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1
Schepanski, Kerstin, Bernd Heinold, and Ina Tegen. "Harmattan, Saharan heat low, and West African monsoon circulation: modulations on the Saharan dust outflow towards the North Atlantic." Atmospheric Chemistry and Physics 17, no. 17 (September 1, 2017): 10223–43. http://dx.doi.org/10.5194/acp-17-10223-2017.
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Abstract. The outflow of dust from the northern African continent towards the North Atlantic is stimulated by the atmospheric circulation over North Africa, which modulates the spatio-temporal distribution of dust source activation and consequently the entrainment of mineral dust into the boundary layer, as well as the transport of dust out of the source regions. The atmospheric circulation over the North African dust source regions, predominantly the Sahara and the Sahel, is characterized by three major circulation regimes: (1) the harmattan (trade winds), (2) the Saharan heat low (SHL), and (3) the West African monsoon circulation. The strength of the individual regimes controls the Saharan dust outflow by affecting the spatio-temporal distribution of dust emission, transport pathways, and deposition fluxes.This study aims at investigating the atmospheric circulation pattern over North Africa with regard to its role favouring dust emission and dust export towards the tropical North Atlantic. The focus of the study is on summer 2013 (June to August), during which the SALTRACE (Saharan Aerosol Long-range TRansport and Aerosol-Cloud interaction Experiment) field campaign also took place. It involves satellite observations by the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) flying on board the geostationary Meteosat Second Generation (MSG) satellite, which are analysed and used to infer a data set of active dust sources. The spatio-temporal distribution of dust source activation frequencies (DSAFs) allows for linking the diurnal cycle of dust source activations to dominant meteorological controls on dust emission. In summer, Saharan dust source activations clearly differ from dust source activations over the Sahel regarding the time of day when dust emission begins. The Sahara is dominated by morning dust source activations predominantly driven by the breakdown of the nocturnal low-level jet. In contrast, dust source activations in the Sahel are predominantly activated during the second half of the day, when downdrafts associated with deep moist convection are the major atmospheric driver. Complementary to the satellite-based analysis on dust source activations and implications from their diurnal cycle, simulations on atmosphere and dust life cycle were performed using the mesoscale atmosphere–dust model system COSMO-MUSCAT (COSMO: COnsortium for Small-scale MOdelling; MUSCAT: MUltiScale Chemistry Aerosol Transport Model). Fields from this simulation were analysed regarding the variability of the harmattan, the Saharan heat low, and the monsoon circulation as well as their impact on the variability of the Saharan dust outflow towards the North Atlantic. This study illustrates the complexity of the interaction among the three major circulation regimes and their modulation of the North African dust outflow. Enhanced westward dust fluxes frequently appear following a phase characterized by a deep SHL. Ultimately, findings from this study contribute to the quantification of the interannual variability of the atmospheric dust burden.
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Mulcahy, Jane P., Colin Johnson, Colin G. Jones, Adam C. Povey, Catherine E. Scott, Alistair Sellar, Steven T. Turnock, et al. "Description and evaluation of aerosol in UKESM1 and HadGEM3-GC3.1 CMIP6 historical simulations." Geoscientific Model Development 13, no. 12 (December 21, 2020): 6383–423. http://dx.doi.org/10.5194/gmd-13-6383-2020.
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Abstract. We document and evaluate the aerosol schemes as implemented in the physical and Earth system models, the Global Coupled 3.1 configuration of the Hadley Centre Global Environment Model version 3 (HadGEM3-GC3.1) and the United Kingdom Earth System Model (UKESM1), which are contributing to the sixth Coupled Model Intercomparison Project (CMIP6). The simulation of aerosols in the present-day period of the historical ensemble of these models is evaluated against a range of observations. Updates to the aerosol microphysics scheme are documented as well as differences in the aerosol representation between the physical and Earth system configurations. The additional Earth system interactions included in UKESM1 lead to differences in the emissions of natural aerosol sources such as dimethyl sulfide, mineral dust and organic aerosol and subsequent evolution of these species in the model. UKESM1 also includes a stratospheric–tropospheric chemistry scheme which is fully coupled to the aerosol scheme, while GC3.1 employs a simplified aerosol chemistry mechanism driven by prescribed monthly climatologies of the relevant oxidants. Overall, the simulated speciated aerosol mass concentrations compare reasonably well with observations. Both models capture the negative trend in sulfate aerosol concentrations over Europe and the eastern United States of America (US) although the models tend to underestimate sulfate concentrations in both regions. Interactive emissions of biogenic volatile organic compounds in UKESM1 lead to an improved agreement of organic aerosol over the US. Simulated dust burdens are similar in both models despite a 2-fold difference in dust emissions. Aerosol optical depth is biased low in dust source and outflow regions but performs well in other regions compared to a number of satellite and ground-based retrievals of aerosol optical depth. Simulated aerosol number concentrations are generally within a factor of 2 of the observations, with both models tending to overestimate number concentrations over remote ocean regions, apart from at high latitudes, and underestimate over Northern Hemisphere continents. Finally, a new primary marine organic aerosol source is implemented in UKESM1 for the first time. The impact of this new aerosol source is evaluated. Over the pristine Southern Ocean, it is found to improve the seasonal cycle of organic aerosol mass and cloud droplet number concentrations relative to GC3.1 although underestimations in cloud droplet number concentrations remain. This paper provides a useful characterisation of the aerosol climatology in both models and will facilitate understanding in the numerous aerosol–climate interaction studies that will be conducted as part of CMIP6 and beyond.
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Pérez, C., K. Haustein, Z. Janjic, O. Jorba, N. Huneeus, J. M. Baldasano, T. Black, et al. "Atmospheric dust modeling from meso to global scales with the online NMMB/BSC-Dust model – Part 1: Model description, annual simulations and evaluation." Atmospheric Chemistry and Physics Discussions 11, no. 6 (June 22, 2011): 17551–620. http://dx.doi.org/10.5194/acpd-11-17551-2011.
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Abstract. We describe and evaluate the NMMB/BSC-Dust, a new dust aerosol cycle model embedded online within the NCEP Non-hydrostatic Multiscale Model (NMMB). NMMB is a further evolution of the operational Non-hydrostatic Mesoscale Model (WRF-NMM), which together with other upgrades has been extended from meso to global scales. Its unified non-hydrostatic dynamical core is prepared for regional and global simulation domains. The new NMMB/BSC-Dust is intended to provide short to medium-range weather and dust forecasts from regional to global scales and represents a first step towards the development of a unified chemical-weather model. This paper describes the parameterizations used in the model to simulate the dust cycle including sources, transport, deposition and interaction with radiation. We evaluate monthly and annual means of the global configuration of the model against the AEROCOM dust benchmark dataset for year 2000 including surface concentration, deposition and aerosol optical depth (AOD), and we evaluate the daily AOD variability in a regional domain at high resolution covering Northern Africa, Middle East and Europe against AERONET AOD for year 2006. The NMMB/BSC-Dust provides a good description of the horizontal distribution and temporal variability of the dust. Daily AOD correlations at the regional scale are around 0.6–0.7 on average without dust data assimilation. At the global scale the model lies within the top range of AEROCOM dust models in terms of performance statistics for surface concentration, deposition and AOD. This paper discusses the current strengths and limitations of the modeling system and points towards future improvements.
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Pérez, C., K. Haustein, Z. Janjic, O. Jorba, N. Huneeus, J. M. Baldasano, T. Black, et al. "Atmospheric dust modeling from meso to global scales with the online NMMB/BSC-Dust model – Part 1: Model description, annual simulations and evaluation." Atmospheric Chemistry and Physics 11, no. 24 (December 21, 2011): 13001–27. http://dx.doi.org/10.5194/acp-11-13001-2011.
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Abstract. We describe and evaluate the NMMB/BSC-Dust, a new dust aerosol cycle model embedded online within the NCEP Non-hydrostatic Multiscale Model (NMMB). NMMB is a further evolution of the operational Non-hydrostatic Mesoscale Model (WRF-NMM), which together with other upgrades has been extended from meso to global scales. Its unified non-hydrostatic dynamical core is prepared for regional and global simulation domains. The new NMMB/BSC-Dust is intended to provide short to medium-range weather and dust forecasts from regional to global scales and represents a first step towards the development of a unified chemical-weather model. This paper describes the parameterizations used in the model to simulate the dust cycle including sources, transport, deposition and interaction with radiation. We evaluate monthly and annual means of the global configuration of the model against the AEROCOM dust benchmark dataset for year 2000 including surface concentration, deposition and aerosol optical depth (AOD), and we evaluate the daily AOD variability in a regional domain at high resolution covering Northern Africa, Middle East and Europe against AERONET AOD for year 2006. The NMMB/BSC-Dust provides a good description of the horizontal distribution and temporal variability of the dust. Daily AOD correlations at the regional scale are around 0.6–0.7 on average without dust data assimilation. At the global scale the model lies within the top range of AEROCOM dust models in terms of performance statistics for surface concentration, deposition and AOD. This paper discusses the current strengths and limitations of the modeling system and points towards future improvements.
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Ayache, Mohamed, Jean-Claude Dutay, Kazuyo Tachikawa, Thomas Arsouze, and Catherine Jeandel. "Neodymium budget in the Mediterranean Sea: evaluating the role of atmospheric dusts using a high-resolution dynamical-biogeochemical model." Biogeosciences 20, no. 1 (January 16, 2023): 205–27. http://dx.doi.org/10.5194/bg-20-205-2023.
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Abstract. The relative importance of river solid discharge, deposited sediment remobilisation, and atmospheric dust as sources of neodymium (Nd) to the ocean is the subject of ongoing debate, the magnitudes of these fluxes being associated with a significant uncertainty. The Mediterranean basin is a specific basin; it receives a vast amount of emissions from different sources and is surrounded by continental margins, with a significant input of dust as compared to the global ocean. Furthermore, it is largely impacted by the Atlantic water inflow via the Strait of Gibraltar. Here, we present the first simulation of dissolved Nd concentration ([Nd]) and Nd isotopic composition (εNd) using a high-resolution regional model (NEMO/MED12/PISCES) with an explicit representation of all Nd inputs, and the internal cycle, i.e. the interactions between the particulate and dissolved phases. The high resolution of the oceanic model (at 1/12∘), essential to the simulation of a realistic Mediterranean circulation in present-day conditions, gives a unique opportunity to better apprehend the processes governing the Nd distribution in the marine environment. The model succeeds in simulating the main features of εNd and produces a realistic distribution of [Nd] in the Mediterranean Sea. We estimated the boundary exchange (BE, which represents the transfer of elements from the margin to the sea and their removal by scavenging) flux at 89.43 × 106 g(Nd) yr−1, representing ∼84.4 % of the total external Nd source to the Mediterranean basin. The river discharge provided 3.66 × 106 g(Nd) yr−1, or 3.5 % of the total Nd flow into the Mediterranean. The flux of Nd from partially dissolved atmospheric dusts was estimated at 5.2 × 106 g(Nd) yr−1, representing 5 % of the total Nd input, and 7.62 × 106 g(Nd) yr−1 comes from the Atlantic across the Strait of Gibraltar, i.e. 7.1 % of the total Nd input. The total quantity of Nd in the Mediterranean Sea was estimated to 7.28 × 109 g(Nd); this leads to a new calculated Nd residence time of ∼68 year. This work highlights that the impact of river discharge on [Nd] is localised near the catchments of the main rivers. In contrast, the atmospheric dust input has a basin-wide influence, correcting for a too-radiogenic εNd when only the BE input is considered and improving the agreement of simulated dissolved Nd concentration with field data. This work also suggests that εNd is sensitive to the spatial distribution of Nd in the atmospheric dust, and that the parameterisation of the vertical cycling (scavenging/remineralisation) considerably constrains the ability of the model to simulate the vertical profile of εNd.
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Ragusa, Enrico, Daniele Fasano, Claudia Toci, Gaspard Duchêne, Nicolás Cuello, Marion Villenave, Gerrit van der Plas, et al. "Circumbinary and circumstellar discs around the eccentric binary IRAS 04158+2805 — a testbed for binary–disc interaction." Monthly Notices of the Royal Astronomical Society 507, no. 1 (July 30, 2021): 1157–74. http://dx.doi.org/10.1093/mnras/stab2179.
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ABSTRACT IRAS 04158+2805 has long been thought to be a very low mass T-Tauri star (VLMS) surrounded by a nearly edge-on, extremely large disc. Recent observations revealed that this source hosts a binary surrounded by an extended circumbinary disc with a central dust cavity. In this paper, we combine ALMA multiwavelength observations of continuum and 12CO line emission, with H α imaging and Keck astrometric measures of the binary to develop a coherent dynamical model of this system. The system features an azimuthal asymmetry detected at the western edge of the cavity in Band 7 observations and a wiggling outflow. Dust emission in ALMA Band 4 from the proximity of the individual stars suggests the presence of marginally resolved circumstellar discs. We estimate the binary orbital parameters from the measured arc of the orbit from Keck and ALMA astrometry. We further constrain these estimates using considerations from binary–disc interaction theory. We finally perform three SPH gas+dust simulations based on the theoretical constraints; we post-process the hydrodynamic output using radiative transfer Monte Carlo methods and directly compare the models with observations. Our results suggest that a highly eccentric e ∼ 0.5–0.7 equal mass binary, with a semimajor axis of ∼55 au, and small/moderate orbital plane versus circumbinary disc inclination θ ≲ 30° provides a good match with observations. A dust mass of ${\sim}1.5\times 10^{-4} \, {\rm M_\odot }$ best reproduces the flux in Band 7 continuum observations. Synthetic CO line emission maps qualitatively capture both the emission from the central region and the non-Keplerian nature of the gas motion in the binary proximity.
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Spyrou, C., G. Kallos, C. Mitsakou, P. Athanasiadis, C. Kalogeri, and M. Iacono. "Radiative effects of desert dust on weather and regional climate." Atmospheric Chemistry and Physics Discussions 13, no. 1 (January 11, 2013): 1327–65. http://dx.doi.org/10.5194/acpd-13-1327-2013.
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Abstract. Mineral dust aerosols exert a significant effect on both solar and terrestrial radiation. By absorbing and scattering the solar radiation aerosols reduce the amount of energy reaching the surface. In addition, aerosols enhance the greenhouse effect by absorbing and emitting outgoing longwave radiation. Desert dust forcing exhibits large regional and temporal variability due to its short lifetime and diverse optical properties, further complicating the quantification of the Direct Radiative Effect (DRE). The complexity of the links and feedbacks of dust on radiative transfer indicate the need of an integrated approach in order to examine these impacts. In order to examine these feedbacks, the SKIRON limited area model has been upgraded to include the RRTMG (Rapid Radiative Transfer Model – GCM) radiative transfer model that takes into consideration the aerosol radiative effects. It was run for a 6 yr period. Two sets of simulations were performed, one without the effects of dust and the other including the radiative feedback. The results were first evaluated using aerosol optical depth data to examine the capabilities of the system in describing the desert dust cycle. Then the aerosol feedback on radiative transfer has been quantified and the links between dust and radiation have been studied. The study has revealed a strong interaction between dust particles and solar and terrestrial radiation, with several implications on the energy budget of the atmosphere. A profound effect is the increased absorption (in the shortwave and longwave) in the lower troposphere and the induced modification of the atmospheric temperature profile. These feedbacks depend strongly on the spatial distribution of dust and have more profound effects where the number of particles is greater, such as near their source.
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Spyrou, C., G. Kallos, C. Mitsakou, P. Athanasiadis, C. Kalogeri, and M. J. Iacono. "Modeling the radiative effects of desert dust on weather and regional climate." Atmospheric Chemistry and Physics 13, no. 11 (June 4, 2013): 5489–504. http://dx.doi.org/10.5194/acp-13-5489-2013.
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Abstract. Mineral dust aerosols exert a significant effect on both solar and terrestrial radiation. By absorbing and scattering, the solar radiation aerosols reduce the amount of energy reaching the surface. In addition, aerosols enhance the greenhouse effect by absorbing and emitting outgoing longwave radiation. Desert dust forcing exhibits large regional and temporal variability due to its short lifetime and diverse optical properties, further complicating the quantification of the direct radiative effect (DRE). The complexity of the links and feedbacks of dust on radiative transfer indicate the need for an integrated approach in order to examine these impacts. In order to examine these feedbacks, the SKIRON limited area model has been upgraded to include the RRTMG (Rapid Radiative Transfer Model – GCM) radiative transfer model that takes into consideration the aerosol radiative effects. It was run for a 6 year period. Two sets of simulations were performed, one without the effects of dust and the other including the radiative feedback. The results were first evaluated using aerosol optical depth data to examine the capabilities of the system in describing the desert dust cycle. Then the aerosol feedback on radiative transfer was quantified and the links between dust and radiation were studied. The study has revealed a strong interaction between dust particles and solar and terrestrial radiation, with several implications on the energy budget of the atmosphere. A profound effect is the increased absorption (in the shortwave and longwave) in the lower troposphere and the induced modification of the atmospheric temperature profile. These feedbacks depend strongly on the spatial distribution of dust and have more profound effects where the number of particles is greater, such as near their source.
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Poletaev, N. L. "The heating of a stream of particles by thermal counter radiation." Pozharovzryvobezopasnost/Fire and Explosion Safety 30, no. 2 (May 15, 2021): 15–22. http://dx.doi.org/10.22227/pvb.2021.30.02.15-22.
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Introduction. It is accepted that the depth of heating of the dust/gas/air mixture by the radiation of combustion products SR is equal to the length LR of the free path of radiation in the mixture. Numerical simulation of combustion of a gas-air mixture that has inert particles, taking into account the re-radiation of heat by heated particles of the fresh mixture, led to ratio SR >> LR. In this work, the analytical assessment of ratio χS = SR/LR is performed.One-dimensional problem model. The co-authors determined stationary temperature distribution over the flow of initially cold monodisperse particles suspended in vacuum. Particle velocity V is directed toward a heat-radiating, absolutely black surface that is permeable by particles. Simplifying assumptions are used: radiation consists of two oppositely-directed flows of electromagnetic energy; interaction between particles and radiation is described in the approximation of geometric optics; the temperature inside the particle is the same. Problem solving. It is shown that χS is determined by V=Vcp / (εT 0,5, σTb)3 , where cp, εT, σ, Tb are, respectively, heat capacity per unit volume of the suspended matter, integral emissivity of the particle material, the Stefan-Boltzmann constant, and the surface temperature. For ≤ 2.8, re-emission can be neglected: χS ≈ 1. At ≤ 1.2, temperature distribution regulates re-emission: χS ≈ 5 –1/(2 – εT) >> 1.Solution discussion. The analytical solution satisfactorily describes the available numerical solutions and experimental data for the case of combustion of a dust/gas/air mixture after specifying the parameters of a simplified model: the radiating surface should be understood as the flame front, Tb is the combustion temperature, and cp is the overall heat capacity of the mixture. The estimate ≤ 1.2 indicates the final high temperature of the gas suspension, the possibility of its autoignition far from the flame, and the need to change initial assumptions when simulating re-emission.Conclusions. Analytical evaluations make it possible to employ ratios SR >> LR and SR ≈ LR for the suspension over a thermal radiation source in vacuum. Conditions for the application of the results of simplified simulation of re-emission to the combustion of a dust/gas/air mixture are formulated.
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Shrestha, Prabhakar, Jana Mendrok, and Dominik Brunner. "Aerosol characteristics and polarimetric signatures for a deep convective storm over the northwestern part of Europe – modeling and observations." Atmospheric Chemistry and Physics 22, no. 21 (November 3, 2022): 14095–117. http://dx.doi.org/10.5194/acp-22-14095-2022.
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Abstract. The Terrestrial Systems Modeling Platform (TSMP) was extended with a chemical transport model and polarimetric radar forward operator to enable detailed studies of aerosol–cloud–precipitation interactions. The model was used at kilometer-scale (convection-permitting) resolution to simulate a deep convective storm event over Germany which produced large hail, high precipitation, and severe damaging winds. The ensemble model simulation was, in general, able to capture the storm structure, its evolution, and the spatial pattern of accumulated precipitation. However, the model was found to underestimate regions of high accumulated precipitation (> 35 mm) and convective area fraction in the early period of the storm. While the model tends to simulate too high reflectivity in the downdraft region of the storm above the melting layer (mostly contributed by graupel), the model also simulates very weak polarimetric signatures in this region, when compared to the radar observations. The above findings remained almost unchanged when using a narrower cloud drop size distribution (CDSD) acknowledging the missing feedback between aerosol physical and chemical properties and CDSD shape parameters. The kilometer-scale simulation showed that the strong updraft in the convective core produces aerosol-tower-like features, increasing the aerosol number concentrations and hence increasing the cloud droplet number concentration and reducing the mean cloud drop size. This could also be a source of discrepancy between the simulated polarimetric features like differential reflectivity (ZDR) and specific differential-phase (KDP) columns along the vicinity of the convective core compared to the X-band radar observations. However, the use of narrow CDSD did improve the simulation of ZDR columns. Besides, the evaluation of simulated trace gases and aerosols was encouraging; however, a low bias was observed for aerosol optical depth (AOD), which could be partly linked to an underestimation of dust mass in the forcing data associated with a Saharan dust event. This study illustrates the importance and the additional complexity associated with the inclusion of chemistry transport model when studying aerosol–cloud–precipitation interactions. But, along with polarimetric radar data for model evaluation, it allows us to identify and better constrain the traditional two-moment bulk cloud microphysical schemes used in the numerical weather prediction models for weather and climate.
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Kannan, R., E. Garaldi, A. Smith, R. Pakmor, V. Springel, M. Vogelsberger, and L. Hernquist. "Introducing the thesan project: radiation-magnetohydrodynamic simulations of the epoch of reionization." Monthly Notices of the Royal Astronomical Society 511, no. 3 (December 27, 2021): 4005–30. http://dx.doi.org/10.1093/mnras/stab3710.
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ABSTRACT We introduce the thesan project, a suite of large volume ($L_\mathrm{box} = 95.5 \, \mathrm{cMpc}$) radiation-magnetohydrodynamic simulations that simultaneously model the large-scale statistical properties of the intergalactic medium during reionization and the resolved characteristics of the galaxies responsible for it. The flagship simulation has dark matter and baryonic mass resolutions of $3.1 \times 10^6\, {\rm M_\odot }$ and $5.8 \times 10^5\, {\rm M_\odot }$, respectively. The gravitational forces are softened on scales of 2.2 ckpc with the smallest cell sizes reaching 10 pc at z = 5.5, enabling predictions down to the atomic cooling limit. The simulations use an efficient radiation hydrodynamics solver (arepo-rt) that precisely captures the interaction between ionizing photons and gas, coupled to well-tested galaxy formation (IllustrisTNG) and dust models to accurately predict the properties of galaxies. Through a complementary set of medium resolution simulations we investigate the changes to reionization introduced by different assumptions for ionizing escape fractions, varying dark matter models, and numerical convergence. The fiducial simulation and model variations are calibrated to produce realistic reionization histories that match the observed evolution of the global neutral hydrogen fraction and electron scattering optical depth to reionization. They also match a wealth of high-redshift observationally inferred data, including the stellar-to-halo-mass relation, galaxy stellar mass function, star formation rate density, and the mass–metallicity relation, despite the galaxy formation model being mainly calibrated at z = 0. We demonstrate that different reionization models give rise to varied bubble size distributions that imprint unique signatures on the 21 cm emission, especially on the slope of the power spectrum at large spatial scales, enabling current and upcoming 21 cm experiments to accurately characterize the sources that dominate the ionizing photon budget.
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Panfilov, Ivan, Alexey N. Beskopylny, and Besarion Meskhi. "Numerical Simulation of Heat Transfer and Spread of Virus Particles in the Car Interior." Mathematics 11, no. 3 (February 3, 2023): 784. http://dx.doi.org/10.3390/math11030784.
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The epidemic caused by the coronavirus infection SARS-CoV-2 at the beginning of 2022 affected approximately 500 million people in all countries. The source of infection is the particles of the virus, which, when breathing, talking, and coughing, are released with the respiratory droplets and aerosol dust of an infected person. Actions aimed at combating and minimizing the consequences of coronavirus infection led to taking measures in scientific areas to investigate the processes of the spread of viral particles in the air, in ventilation, and air conditioning systems of premises and transport, filtration through masks, the effect of partitions, face shields, etc. The article presents a mathematical model of the spread of viral particles in technological transport. Air intake diverters and the operator’s respiratory tract are the sources of the virus. The Euler–Lagrange approach was used to simulate liquid droplets in a flow. Here, the liquid phase is considered as a continuous medium using Navier–Stokes equations, the continuity equation, the energy equation, and the diffusion equation. Accounting for diffusion makes it possible to explicitly model air humidity and is necessary to consider the evaporation of droplets (changes in the mass and size of particles containing the virus). Liquid droplets are modeled using the discrete-phase model (DPM), in which each particle is tracked in a Lagrange coordinate system. The DPM method is effective, since the volume fraction of particles is small relative to the total volume of the medium, and the interaction of particles with each other can be neglected. In this case, the discrete and continuous phases are interconnected through the source terms in the equations. The averaged RANS equations are solved numerically using the k-ω turbulence model in the Ansys Fluent package. The task was solved in a static form and in the time domain. For a non-stationary problem, the stabilization time of the variables is found. The simulation results are obtained in the form of fields of pressures, velocities, temperatures and air densities, and the field of propagation of particles containing the virus. Various regimes were studied at various free flow rates and initial velocities of droplets with viral particles. The results of trajectories and velocities of particles, and particle concentrations depending on time, size, and on the evaporability of particles are obtained.
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Fajardo-Zambrano, Carlos Mario, Juan Antonio Bravo-Aranda, María José Granados-Muñoz, Elena Montilla-Rosero, Juan Andrés Casquero-Vera, Fernando Rejano, Sonia Castillo, and Lucas Alados-Arboledas. "Lidar and Radar Signal Simulation: Stability Assessment of the Aerosol–Cloud Interaction Index." Remote Sensing 14, no. 6 (March 9, 2022): 1333. http://dx.doi.org/10.3390/rs14061333.
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Aerosol–cloud interactions (ACI) are in the spotlight of atmospheric science since the limited knowledge about these processes produces large uncertainties in climate predictions. These interactions can be quantified by the aerosol–cloud interaction index (ACI index), which establishes a relationship between aerosol and cloud microphysics. The experimental determination of the ACI index through a synergistic combination of lidar and cloud radar is still quite challenging due to the difficulties in disentangling the aerosol influence on cloud formation from other processes and in retrieving aerosol-particle and cloud microphysics from remote sensing measurements. For a better understanding of the ACI and to evaluate the optimal experimental conditions for the measurement of these processes, a Lidar and Radar Signal Simulator (LARSS) is presented. LARSS simulate vertically-resolved lidar and cloud-radar signals during the formation process of a convective cloud, from the aerosol hygroscopic enhancement to the condensation droplet growth. Through LARSS simulations, it is observed a dependence of the ACI index with height, associated with the increase in number (ACINd) and effective radius (ACIreff) of the droplets with altitude. Furthermore, ACINd and ACIreff for several aerosol types (such as ammonium sulfate, biomass burning, and dust) are estimated using LARSS, presenting different values as a function of the aerosol model. Minimum ACINd values are obtained when the activation of new droplets stops, while ACIreff reaches its maximum values several meters above. These simulations are carried out considering standard atmospheric conditions, with a relative humidity of 30% at the surface, reaching the supersaturation of the air mass at 3500 m. To assess the stability of the ACI index, a sensitivity study using LARSS is performed. It is obtained that the dry modal aerosol radius presents a strong influence on the ACI index fluctuations of 18% cause an ACI variability of 30% while the updraft velocity within the cloud and the wet modal aerosol radius have a weaker impact. LARSS ACI index uncertainty is obtained through the Monte Carlo technique, obtaining ACIreff uncertainty below 16% for the uncertainty of all LARSS input parameters of 10%. Finally, a new ACI index is introduced in this study, called the remote-sensing ACI index (ACIRs), to simplify the quantification of the ACI processes with remote sensors. This new index presents a linear relationship with the ACIreff, which depends on the Angstrom exponent. The use of ACIRs to derive ACIreff presents the advantage that it is possible to quantify the aerosol–cloud interaction without the need to perform microphysical inversion retrievals, thus reducing the uncertainty sources.
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Stoyanovskaya, Olga P., Vitaliy V. Grigoryev, Anastasiya N. Suslenkova, Maxim N. Davydov, and Nikolay V. Snytnikov. "Two-Phase Gas and Dust Free Expansion: Three-Dimensional Benchmark Problem for CFD Codes." Fluids 7, no. 2 (January 24, 2022): 51. http://dx.doi.org/10.3390/fluids7020051.
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In the computational mechanics of multiphase dispersed flows, there is an issue of computing the interaction between phases in a mixture of a carrier fluid and dispersed inclusions. The problem is that an accurate dynamics simulation of a mixture of gas and finely dispersed solids with intense interphase interaction requires much more computational power compared to pure gas or a mixture with moderate interaction between phases. To tackle this problem, effective numerical methods are being searched for to ensure adequate computational cost, accuracy, and stability of the results at an arbitrary intensity of momentum and energy exchange between phases. Thus, to assess the approximation, dispersive, dissipative, and asymptotic properties of numerical methods, benchmark solutions of relevant test problems are required. Such solutions are known for one-dimensional problems with linear plane waves. We introduce a novel analytical solution for the nonlinear problem of spherically symmetric expansion of a gas and dust ball into a vacuum. Therein, the dynamics of carrier and dispersed phases are modeled using equations for a compressible inviscid gas. Solid particles do not have intrinsic pressure and are assumed to be monodisperse. The carrier and dispersed phases exchange momentum. In the derived solution, the velocities of gas and dust clouds depend linearly on the radii. The results were reproduced at high, moderate, and low momentum exchange between phases using the SPH-IDIC (Smoothed Particle Hydrodynamics with Implicit Drag in Cell) method implemented based on the open-source OpenFPM library. We reported an example of using the solution as a benchmark for CFD (computational fluid dynamics) models verification and for the evaluation of numerical methods. Our benchmark solution generator developed in the free Scilab environment is publicly available.
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Gao, Chao, Aijun Xiu, Xuelei Zhang, Qingqing Tong, Hongmei Zhao, Shichun Zhang, Guangyi Yang, and Mengduo Zhang. "Two-way coupled meteorology and air quality models in Asia: a systematic review and meta-analysis of impacts of aerosol feedbacks on meteorology and air quality." Atmospheric Chemistry and Physics 22, no. 8 (April 22, 2022): 5265–329. http://dx.doi.org/10.5194/acp-22-5265-2022.
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Abstract. Atmospheric aerosols can exert an influence on meteorology and air quality through aerosol–radiation interaction (ARI) and aerosol–cloud interaction (ACI), and this two-way feedback has been studied by applying two-way coupled meteorology and air quality models. As one of the regions with the highest aerosol loading in the world, Asia has attracted many researchers to investigate the aerosol effects with several two-way coupled models (WRF-Chem, WRF-CMAQ, GRAPES-CUACE, WRF-NAQPMS, and GATOR-GCMOM) over the last decade. This paper attempts to offer a bibliographic analysis regarding the current status of applications of two-way coupled models in Asia, related research focuses, model performances, and the effects of ARI and/or ACI on meteorology and air quality. There were a total of 160 peer-reviewed articles published between 2010 and 2019 in Asia meeting the inclusion criteria, with more than 79 % of papers involving the WRF-Chem model. The number of relevant publications has an upward trend annually, and East Asia, India, and China, as well as the North China Plain are the most studied areas. The effects of ARI and both ARI and ACI induced by natural aerosols (particularly mineral dust) and anthropogenic aerosols (bulk aerosols, different chemical compositions, and aerosols from different sources) are widely investigated in Asia. Through the meta-analysis of surface meteorological and air quality variables simulated by two-way coupled models, the model performance affected by aerosol feedbacks depends on different variables, simulation time lengths, selection of two-way coupled models, and study areas. Future research perspectives with respect to the development, improvement, application, and evaluation of two-way coupled meteorology and air quality models are proposed.
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Kok, J. F., N. M. Mahowald, S. Albani, G. Fratini, J. A. Gillies, M. Ishizuka, J. F. Leys, et al. "An improved dust emission model with insights into the global dust cycle's climate sensitivity." Atmospheric Chemistry and Physics Discussions 14, no. 5 (March 11, 2014): 6361–425. http://dx.doi.org/10.5194/acpd-14-6361-2014.
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Abstract. Simulations of the global dust cycle and its interactions with a changing Earth system are hindered by the empirical nature of dust emission parameterizations in climate models. Here we take a step towards improving global dust cycle simulations by presenting a physically-based dust emission model. The resulting dust flux parameterization depends only on the wind friction speed and the soil's threshold friction speed, and can therefore be readily implemented into climate models. We show that our parameterization's functional form is supported by a compilation of quality-controlled vertical dust flux measurements, and that it better reproduces these measurements than existing parameterizations. Both our theory and measurements indicate that many climate models underestimate the dust flux's sensitivity to soil erodibility. This finding can explain why dust cycle simulations in many models are improved by using an empirical preferential sources function that shifts dust emissions towards the most erodible regions. In fact, implementing our parameterization in a climate model produces even better agreement against aerosol optical depth measurements than simulations that use such a source function. These results indicate that the need to use a source function is at least partially eliminated by the additional physics accounted for by our parameterization. Since soil erodibility is affected by climate changes, our results further suggest that many models have underestimated the climate sensitivity of the global dust cycle.
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Iaconi, Roberto, Keiichi Maeda, Orsola De Marco, Takaya Nozawa, and Thomas Reichardt. "Properties of the post-inspiral common envelope ejecta – I. Dynamical and thermal evolution." Monthly Notices of the Royal Astronomical Society 489, no. 3 (August 21, 2019): 3334–50. http://dx.doi.org/10.1093/mnras/stz2312.
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ABSTRACT We investigate the common envelope binary interaction, that leads to the formation of compact binaries, such as the progenitors of Type Ia supernovae or of mergers that emit detectable gravitational waves. In this work, we diverge from the classic numerical approach that models the dynamic inspiral. We focus instead on the asymptotic behaviour of the common envelope expansion after the dynamic inspiral terminates. We use the SPH code phantom to simulate one of the set-ups from Passy et al., with a 0.88 M⊙, 83 R⊙ RGB primary and a 0.6 M⊙ companion, then we follow the ejecta expansion for 50 yr. Additionally, we utilize a tabulated equation of state including the envelope recombination energy in the simulation (Reichardt et al.), achieving a full unbinding. We show that, as time passes, the envelope’s radial velocities dominate over the tangential ones, hence allowing us to apply an homologous expansion kinematic model to the ejecta. The external layers of the envelope become homologous as soon as they are ejected, but it takes 5000 d (14 yr) for the bulk of the unbound gas to achieve the homologously expanding regime. We observe that the complex distribution generated by the dynamic inspiral evolves into a more ordered, shell-like shaped one in the asymptotic regime. We show that the thermodynamics of the expanding envelope are in very good agreement with those expected for an adiabatically expanding sphere under the homologous condition and give a prediction for the location and temperature of the photosphere assuming dust to be the main source of opacity. This technique ploughs the way to determining the long-term light behaviour of common envelope transients.
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Sarkar, Geetanjali, and Raghvendra Sahai. "A Study of the Dusty Disks and Shells around Post-RGB Stars in the LMC." Galaxies 10, no. 2 (April 2, 2022): 56. http://dx.doi.org/10.3390/galaxies10020056.
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A new class of dusty post-Red Giant Branch (post-RGB) stars has recently been identified in the Magellanic Clouds. Their spectral energy distributions (SEDs) suggest that their mass-ejecta are similar to dusty post-Asymptotic Giant Branch (post-AGB) stars. We modeled the SEDs of a select sample of post-RGB and post-AGB stars in the Large Magellanic Cloud (LMC), quantified the total dust mass in the disks and shells and set rough constraints on the dust grain compositions and sizes. The shells were significantly more massive than the disks. Our models suggest that circumstellar disks, when present, are geometrically thick with a substantial opening angle, which is consistent with numerical simulations of CE evolution (CEE). Comparison of our model dust mass values with the predictions of dust production during CEE on the RGB suggest that CEE occurred near or at the tip of the RGB for the post-RGB sources in our sample. Amorphous silicate emission features at 10 and 18 μm are seen in the model spectra of several post-RGBs. A surprising result is that the ejected dust in certain post-RGB sources appears to be carbon-rich, thus, providing independent support for the hypothesis of binary interactions leading to the formation of dusty post-RGB objects.
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Misiorowski, Matthew P., Farhan S. Gandhi, and Assad A. Oberai. "Computational Analysis and Flow Physics of a Ducted Rotor in Edgewise Flight." Journal of the American Helicopter Society 64, no. 4 (October 1, 2019): 1–14. http://dx.doi.org/10.4050/jahs.64.042004.
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This study examines the performance of the ducted rotor in hover and edgewise flight conditions. The flow over a threedimensional model of a ducted rotor was simulated using the Spalart–Allmaras Reynolds-averaged Navier–Stokes model implemented in a stabilized finite element method. A sliding mesh was used to conveniently account for the large-scale motion associated with rotor revolutions. The simulation results were analyzed to understand the flow physics and quantify the contributions of the rotor and various sections of the duct interior surfaces on the total aerodynamic forces (thrust, drag, and side force) and moments (pitching and rolling). In edgewise flight, freestream flow separates off the front of the duct inlet, causing a region of recirculating flow and upwash in the rotor plane. The upwash region biases rotor thrust production to the front of the disk. The swirl velocity further biases the region of flow separation over the inlet and upwash at the front of the rotor toward the retreating side of the disk. The shift of thrust production on the rotor and duct toward the front produces a strong nose-up pitching moment on the ducted rotor. The rear of the diffuser is a significant contributor to the total drag; this force includes a nose-down pitch moment, which partially negates the moment from the duct inlet. The rotor is the primary source of vertical vibratory forces as well as vibratory pitching and rolling moments. The small tip clearance of the rotor causes a local interaction between the blade tip and duct that is the dominant contributor to in-plane vibratory forces on the ducted rotor.
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Sarkar, Geetanjali, and Raghvendra Sahai. "Common Envelope Mass Ejection in Evolved Stars: Modeling the Dust Emission from Post-RGB Stars in the LMC." Astrophysical Journal 940, no. 1 (November 1, 2022): 54. http://dx.doi.org/10.3847/1538-4357/ac8d03.
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Abstract Common envelope (CE) systems are the result of Roche lobe overflow in interacting binaries. The subsequent evolution of the CE, its ejection, and the formation of dust in its ejecta while the primary is on the red giant branch (RGB) gives rise to a recently identified evolutionary class—dusty post-RGB stars. Their spectral energy distributions (SEDs) suggest that their mass-ejecta are similar to dusty post-asymptotic giant branch (post-AGB) stars. We have modeled the SEDs of a select sample of post-RGB and post-AGB stars in the Large Magellanic Cloud, quantified the total dust mass (and gas mass assuming gas-to-dust ratio) in the disks and shells and set constraints on the dust grain compositions and sizes. We find that the shell masses in the post-RGBs are generally less than those in post-AGBs, with the caveat that substantial amount of mass in both types of objects may lie in cold, extended shells. Our models suggest that circumstellar disks, when present, are geometrically thick structures with a substantial opening angle, consistent with numerical simulations of CE evolution (CEE). Comparison of our model dust masses with the predictions of dust production during CEE on the RGB suggest that CEE occurred near or at the tip of the RGB for our post-RGB sources. A surprising result is that some post-RGB stars harbor carbon-rich dust, believed to form when C/O > 1, e.g., following triple-alpha nucleosynthesis and third dredge-up events in AGB stars. This anomaly strengthens the hypothesis that dusty post-RGBs are born in binary systems.
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Wu, Chenglai, Zhaohui Lin, and Xiaohong Liu. "The global dust cycle and uncertainty in CMIP5 (Coupled Model Intercomparison Project phase 5) models." Atmospheric Chemistry and Physics 20, no. 17 (September 8, 2020): 10401–25. http://dx.doi.org/10.5194/acp-20-10401-2020.
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Abstract. The dust cycle is an important component of the Earth system and has been implemented in climate models and Earth system models (ESMs). An assessment of the dust cycle in these models is vital to address their strengths and weaknesses in simulating dust aerosol and its interactions with the Earth system and enhance the future model developments. This study presents a comprehensive evaluation of the global dust cycle in 15 models participating in the fifth phase of the Coupled Model Intercomparison Project (CMIP5). The various models are compared with each other and with an aerosol reanalysis as well as station observations. The results show that the global dust emission in these models varies by a factor of 4–5 for the same size range. The models generally agree with each other and observations in reproducing the “dust belt”, which extends from North Africa, the Middle East, Central and South Asia to East Asia, although they differ greatly in the spatial extent of this dust belt. The models also differ in other dust source regions such as North America and Australia. We suggest that the coupling of dust emission with dynamic vegetation can enlarge the range of simulated dust emission. For the removal process, all the models estimate that wet deposition is smaller than dry deposition and wet deposition accounts for 12 %–39 % of total deposition. The models also estimate that most (77 %–91 %) dust particles are deposited onto continents and 9 %–23 % of dust particles are deposited into oceans. Compared to the observations, most models reproduce the dust deposition and dust concentrations within a factor of 10 at most stations, but larger biases by more than a factor of 10 are also noted at specific regions and for certain models. These results highlight the need for further improvements of the dust cycle especially on dust emission in climate models.
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Wu, Longtao, Yu Gu, Jonathan H. Jiang, Hui Su, Nanpeng Yu, Chun Zhao, Yun Qian, Bin Zhao, Kuo-Nan Liou, and Yong-Sang Choi. "Impacts of aerosols on seasonal precipitation and snowpack in California based on convection-permitting WRF-Chem simulations." Atmospheric Chemistry and Physics 18, no. 8 (April 23, 2018): 5529–47. http://dx.doi.org/10.5194/acp-18-5529-2018.
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Abstract. A version of the WRF-Chem model with fully coupled aerosol–meteorology–snowpack is employed to investigate the impacts of various aerosol sources on precipitation and snowpack in California. In particular, the impacts of locally emitted anthropogenic and dust aerosols, and aerosols transported from outside California are studied. We differentiate three pathways of aerosol effects: aerosol–radiation interaction (ARI), aerosol–snow interaction (ASI), and aerosol–cloud interaction (ACI). The convection-permitting model simulations show that precipitation, snow water equivalent (SWE), and surface air temperature averaged over the whole domain (34–42∘ N, 117–124∘ W, not including ocean points) are reduced when aerosols are included, therefore reducing large biases in these variables due to the absence of aerosol effects in the model. Aerosols affect California water resources through the warming of mountaintops and the reduction of precipitation; however, different aerosol sources play different roles in changing surface temperature, precipitation, and snowpack in California by means of various weights of the three pathways. ARI by all aerosols mainly cools the surface, leading to slightly increased SWE over the mountains. Locally emitted dust aerosols warm the surface of mountaintops through ASI, in which the reduced snow albedo associated with dusty snow leads to more surface absorption of solar radiation and reduced SWE. Transported aerosols and local anthropogenic aerosols play a dominant role in increasing nonprecipitating clouds but reducing precipitation through ACI, leading to reduced SWE and runoff on the Sierra Nevada, as well as the warming of mountaintops associated with decreased SWE and hence lower surface albedo. The average changes in surface temperature from October 2012 to June 2013 are about −0.19 and 0.22 K for the whole domain and over mountaintops, respectively. Overall, the averaged reduction during October to June is about 7 % for precipitation, 3 % for SWE, and 7 % for surface runoff for the whole domain, while the corresponding numbers are 12, 10, and 10 % for the mountaintops. The reduction in SWE is more significant in a dry year, with 9 % for the whole domain and 16 % for the mountaintops. The maximum reduction of ∼ 20 % in precipitation occurs in May and is associated with the maximum aerosol loading, leading to the largest decrease in SWE and surface runoff over that period. It is also found that dust aerosols can cause early snowmelt on the mountaintops and reduced surface runoff after April.
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Klose, Martina, Oriol Jorba, María Gonçalves Ageitos, Jeronimo Escribano, Matthew L. Dawson, Vincenzo Obiso, Enza Di Tomaso, et al. "Mineral dust cycle in the Multiscale Online Nonhydrostatic AtmospheRe CHemistry model (MONARCH) Version 2.0." Geoscientific Model Development 14, no. 10 (October 25, 2021): 6403–44. http://dx.doi.org/10.5194/gmd-14-6403-2021.
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Abstract. We present the dust module in the Multiscale Online Non-hydrostatic AtmospheRe CHemistry model (MONARCH) version 2.0, a chemical weather prediction system that can be used for regional and global modeling at a range of resolutions. The representations of dust processes in MONARCH were upgraded with a focus on dust emission (emission parameterizations, entrainment thresholds, considerations of soil moisture and surface cover), lower boundary conditions (roughness, potential dust sources), and dust–radiation interactions. MONARCH now allows modeling of global and regional mineral dust cycles using fundamentally different paradigms, ranging from strongly simplified to physics-based parameterizations. We present a detailed description of these updates along with four global benchmark simulations, which use conceptually different dust emission parameterizations, and we evaluate the simulations against observations of dust optical depth. We determine key dust parameters, such as global annual emission/deposition flux, dust loading, dust optical depth, mass-extinction efficiency, single-scattering albedo, and direct radiative effects. For dust-particle diameters up to 20 µm, the total annual dust emission and deposition fluxes obtained with our four experiments range between about 3500 and 6000 Tg, which largely depend upon differences in the emitted size distribution. Considering ellipsoidal particle shapes and dust refractive indices that account for size-resolved mineralogy, we estimate the global total (longwave and shortwave) dust direct radiative effect (DRE) at the surface to range between about −0.90 and −0.63 W m−2 and at the top of the atmosphere between −0.20 and −0.28 W m−2. Our evaluation demonstrates that MONARCH is able to reproduce key features of the spatiotemporal variability of the global dust cycle with important and insightful differences between the different configurations.
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Zhang, D. F., A. S. Zakey, X. J. Gao, F. Giorgi, and F. Solmon. "Simulation of dust aerosol and its regional feedbacks over East Asia using a regional climate model." Atmospheric Chemistry and Physics 9, no. 4 (February 16, 2009): 1095–110. http://dx.doi.org/10.5194/acp-9-1095-2009.
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Abstract. The ICTP regional climate model (RegCM3) coupled with a desert dust aerosol model is used to simulate the net radiative forcing (short-wave and long-wave) and related climate effects of dust aerosols over East Asia. Two sets of experiments are completed and intercompared, one without (Exp. 1) and one with (Exp. 2) the radiative effects of dust aerosols. The experiments encompass the main dust producing months, February through May, for 10 years (1997–2006), and the simulation results are evaluated against ground station and satellite data. The model captures the basic observed climatology over the area of interest. The spatial and temporal variations of near surface concentration, mass load, optical depth and emission of dust aerosols from the main source regions are reproduced by model. The main model deficiency is an overestimate of dust amounts over the source regions and an underestimate downwind of these source areas, which indicates an underestimate of dust dispersal. Over the desert source regions, the net TOA radiative forcing is positive, while it is small over the other regions as a result of high surface albedo values which reduce the short-wave radiative forcing. The net surface radiative fluxes are decreased by dust and this causes a surface cooling locally up to −1°C. The inclusion of net (short-wave and long-wave) dust radiative forcing leads to a reduction of dust emission in the East Asia source regions, which is mainly caused by an increase in local stability and a corresponding decrease in dust lifting. Our results indicate that dust effects should be included in the assessment of climate change over East Asia.
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Zhang, D. F., A. S. Zakey, X. J. Gao, and F. Giorgi. "Simulation of dust aerosol and its regional feedbacks over East Asia using a regional climate model." Atmospheric Chemistry and Physics Discussions 8, no. 2 (March 4, 2008): 4625–67. http://dx.doi.org/10.5194/acpd-8-4625-2008.
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Abstract. The ICTP regional climate model (RegCM3) coupled with a desert dust model is used to simulate the radiative forcing and related climate effects of dust aerosols over East Asia. Two sets of experiments encompassing the main dust producing months, February to May, for 10 years (1997–2006) are conducted and inter-compared, one without (Exp. 1) and one with (Exp. 2) the radiative effects of dust aerosols. The simulation results are evaluated against ground station and satellite data. The model captures the basic observed climatology over the area of interest. The spatial and temporal variations of near surface concentration, mass load, and emission of dust aerosols from the main source regions are reproduced by model, with the main model deficiency being an overestimate of dust amount over the source regions and underestimate downwind of these source areas. Both the top-of-the-atmosphere (TOA) and surface radiative fluxes are decreased by dust and this causes a surface cooling locally up to −1°C. The inclusion of dust radiative forcing leads to a reduction of dust emission in the East Asia source regions, which is mainly caused by an increase in local stability and a corresponding decrease in dust lifting. Our results indicate that dust effects should be included in the assessment of climate change over East Asia.
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Palacios-Peña, Laura, Rocío Baró, Juan Luis Guerrero-Rascado, Lucas Alados-Arboledas, Dominik Brunner, and Pedro Jiménez-Guerrero. "Evaluating the representation of aerosol optical properties using an online coupled model over the Iberian Peninsula." Atmospheric Chemistry and Physics 17, no. 1 (January 5, 2017): 277–96. http://dx.doi.org/10.5194/acp-17-277-2017.
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Abstract. The effects of atmospheric aerosol particles on the Earth's climate mainly depend on their optical, microphysical and chemical properties, which modify the Earth's radiative budget. The aerosol radiative effects can be divided into direct and semi-direct effects, produced by the aerosol–radiation interactions (ARIs), and indirect effects, produced by aerosol–cloud interactions (ACIs). In this sense the objective of this work is to assess whether the inclusion of aerosol radiative feedbacks in the online coupled WRF-Chem model improves the modelling outputs over the Iberian Peninsula (IP) and surrounding water areas. For this purpose, the methodology is based on the evaluation of modelled aerosol optical properties under different simulation scenarios. The evaluated data come from two WRF-Chem simulations for the IP differing in the inclusion/no-inclusion of ARIs and ACIs (RF/NRF simulations). The case studies cover two episodes with different aerosol types over the IP in 2010, namely a Saharan dust outbreak and a forest fire episode. The evaluation uses observational data from AERONET (Aerosol Robotic Network) stations and MODIS (Moderate Resolution Imaging Spectroradiometer) sensor, including aerosol optical depth (AOD) and Ångström exponent (AE). Experimental data of aerosol vertical distribution from the EARLINET (European Aerosol Research Lidar Network) Granada station are used for checking the models. The results indicate that for the spatial distribution the best-represented variable is AOD and the largest improvements when including the aerosol radiative feedbacks are found for the vertical distribution. In the case of the dust outbreak, a slight improvement (worsening) is produced over the areas with medium (high/low) levels of AOD(−9 % / +12 % of improvement) when including the aerosol radiative feedbacks. For the wildfire episode, improvements of AOD representation (up to 11 %) over areas further away from emission sources are estimated, which compensates for the computational effort of including aerosol feedbacks in the simulations. No clear improvement is observed for the AE representation, the variability of which is largely underpredicted by both simulations.
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Wagner, Robert, Michael Jähn, and Kerstin Schepanski. "Wildfires as a source of airborne mineral dust – revisiting a conceptual model using large-eddy simulation (LES)." Atmospheric Chemistry and Physics 18, no. 16 (August 20, 2018): 11863–84. http://dx.doi.org/10.5194/acp-18-11863-2018.
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Abstract. Airborne mineral dust is a key player in the Earth system and shows manifold impacts on atmospheric properties such as the radiation budget and cloud microphysics. Investigations of smoke plumes originating from wildfires found significant fractions of mineral dust within these plumes – most likely raised by strong, turbulent fire-related winds. This study presents and revisits a conceptual model describing the emission of mineral dust particles during wildfires. This is achieved by means of high-resolution large-eddy simulation (LES), conducted with the All Scale Atmospheric Model (ASAM). The impact of (a) different fire properties representing idealized grassland and shrubland fires, (b) different ambient wind conditions modulated by the fire's energy flux, and (c) the wind's capability to mobilize mineral dust particles was investigated. Results from this study illustrate that the energy release of the fire leads to a significant increase in near-surface wind speed, which consequently enhances the dust uplift potential. This is in particular the case within the fire area where vegetation can be assumed to be widely removed and uncovered soil is prone to wind erosion. The dust uplift potential is very sensitive to fire properties, such as fire size, shape, and intensity, but also depends on the ambient wind velocity. Although measurements already showed the importance of wildfires for dust emissions, pyro-convection is so far neglected as a dust emission process in atmosphere–aerosol models. The results presented in this study can be seen as the first step towards a systematic parameterization representing the connection between typical fire properties and related dust emissions.
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Tabone, B., A. Raga, S. Cabrit, and G. Pineau des Forêts. "Interaction between a pulsating jet and a surrounding disk wind." Astronomy & Astrophysics 614 (June 2018): A119. http://dx.doi.org/10.1051/0004-6361/201732031.
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Context. The molecular richness of fast protostellar jets within 20–100 au of their source, despite strong ultraviolet irradiation, remains a challenge for the models investigated so far. Aim.We aim to investigate the effect of interaction between a time-variable jet and a surrounding steady disk wind, to assess the possibility of jet chemical enrichement by the wind, and the characteristic signatures of such a configuration. Methods. We have constructed an analytic model of a jet bow shock driven into a surrounding slower disk wind in the thin shell approximation. The refilling of the post bow shock cavity from below by the disk wind is also studied. An extension of the model to the case of two or more successive internal working surfaces (IWS) is made. We then compared this analytic model with numerical simulations with and without a surrounding disk wind. Results. We find that at early times (of order the variability period), jet bow shocks travel in refilled pristine disk wind material, before interacting with the cocoon of older bow shocks. This opens the possibility of bow shock chemical enrichment (if the disk wind is molecular and dusty) and of probing the unperturbed disk wind structure near the jet base. Several distinctive signatures of the presence of a surrounding disk wind are identified, in the bow shock morphology and kinematics. Numerical simulations validate our analytical approach and further show that at large scale, the passage of many jet IWS inside a disk wind produces a stationary V-shaped cavity, closing down onto the axis at a finite distance from the source.
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Flock, Mario, and Andrea Mignone. "Streaming instability in a global patch simulation of protoplanetary disks." Astronomy & Astrophysics 650 (June 2021): A119. http://dx.doi.org/10.1051/0004-6361/202040104.
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Aims. In recent years, sub-millimeter (mm) observations of protoplanetary disks have revealed an incredible diversity of substructures in the dust emission. An important result was the finding that dust grains of mm size are embedded in very thin dusty disks. This implies that the dust mass fraction in the midplane becomes comparable to that of the gas, increasing the importance of the interaction between the two components there. Methods. We use numerical 2.5D simulations to study the interaction between gas and dust in fully globally stratified disks. To this end, we employ the recently developed dust grain module of the PLUTO code. Our model focuses on a typical T Tauri disk model, simulating a short patch of the disk at 10 au which includes grains of a constant Stokes number of St = 0.01 and St = 0.1, corresponding to grains with sizes of 0.9 cm and 0.9 mm, respectively, for the given disk model. Results. By injecting a constant pebble flux at the outer domain, the system reaches a quasi-steady state of turbulence and dust concentrations driven by the streaming instability. For our given setup, and using resolutions up to 2500 cells per scale height, we resolve the streaming instability that leads to local dust clumping and concentrations. Our results show dust density values of around 10–100 times the gas density with a steady-state pebble flux of between 3.5 × 10−4 and 2.5 × 10−3 MEarth yr−1 for the models with St = 0.01 and St = 0.1. Conclusions. Grain size and pebble flux for model St = 0.01 compare well with dust evolution models of the first million years of disk evolution. For those grains, the scatter opacity dominates the extinction coefficient at mm wavelengths. These types of global dust and gas simulations are a promising tool for studies of the gas and dust evolution at pressure bumps in protoplanetary disks.
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Nersesian, Angelos, Sébastien Viaene, Ilse De Looze, Maarten Baes, Emmanuel M. Xilouris, Matthew W. L. Smith, Simone Bianchi, et al. "High-resolution, 3D radiative transfer modelling." Astronomy & Astrophysics 643 (November 2020): A90. http://dx.doi.org/10.1051/0004-6361/202038939.
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Context. Investigating the dust heating mechanisms in galaxies provides a deeper understanding of how the internal energy balance drives their evolution. Over the last decade radiative transfer simulations based on the Monte Carlo method have emphasised the role of the various stellar populations heating the diffuse dust. Beyond the expected heating through ongoing star formation, older stellar populations (≥8 Gyr) and even active galactic nuclei can both contribute energy to the infrared emission of diffuse dust. Aims. In this particular study we examine how the radiation of an external heating source, such as the less massive galaxy NGC 5195 in the M 51 interacting system, could affect the heating of the diffuse dust of its parent galaxy NGC 5194, and vice versa. Our goal is to quantify the exchange of energy between the two galaxies by mapping the 3D distribution of their radiation field. Methods. We used SKIRT, a state-of-the-art 3D Monte Carlo radiative transfer code, to construct the 3D model of the radiation field of M 51, following the methodology defined in the DustPedia framework. In the interest of modelling, the assumed centre-to-centre distance separation between the two galaxies is ∼10 kpc. Results. Our model is able to reproduce the global spectral energy distribution of the system, and it matches the resolved optical and infrared images fairly well. In total, 40.7% of the intrinsic stellar radiation of the combined system is absorbed by dust. Furthermore, we quantify the contribution of the various dust heating sources in the system, and find that the young stellar population of NGC 5194 is the predominant dust-heating agent, with a global heating fraction of 71.2%. Another 23% is provided by the older stellar population of the same galaxy, while the remaining 5.8% has its origin in NGC 5195. Locally, we find that the regions of NGC 5194 closer to NGC 5195 are significantly affected by the radiation field of the latter, with the absorbed energy fraction rising up to 38%. The contribution of NGC 5195 remains under the percentage level in the outskirts of the disc of NGC 5194. This is the first time that the heating of the diffuse dust by a companion galaxy is quantified in a nearby interacting system.
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Vukovic, A., M. Vujadinovic, G. Pejanovic, J. Andric, M. R. Kumjian, V. Djurdjevic, M. Dacic, et al. "Numerical simulation of "An American Haboob"." Atmospheric Chemistry and Physics Discussions 13, no. 10 (October 10, 2013): 26175–215. http://dx.doi.org/10.5194/acpd-13-26175-2013.
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Abstract. A dust storm of fearful proportions hit Phoenix in the early evening hours of 5 July 2011. This storm, an American haboob, was predicted hours in advance because numerical, land-atmosphere modeling, computing power and remote sensing of dust events have improved greatly over the past decade. High resolution numerical models are required for accurate simulation of the small-scales of the haboob process, with high velocity surface winds produced by strong convection and severe downbursts. Dust productive areas in this region consist mainly of agricultural fields, with soil surfaces disturbed by plowing and tracks of land in the high Sonoran desert laid barren by ongoing draught. Model simulation of the 5 July 2011 dust storm uses the coupled atmospheric-dust model NMME-DREAM with 3.5 km horizontal resolution. A mask of the potentially dust productive regions is obtained from the land cover and the Normalized Difference Vegetation Index (NDVI) data from the Moderate Resolution Imaging Spectroradiometer (MODIS). Model results are compared with radar and other satellite-based images and surface meteorological and PM10 observations. The atmospheric model successfully hindcasted the position of the front in space and time, with about 1 h late arrival in Phoenix. The dust model predicted the rapid uptake of dust and high values of dust concentration in the ensuing storm. South of Phoenix, over the closest source regions (~ 25 km), the model PM10 surface dust concentration reached ~ 2500 μg m−3, but underestimated the values measured by the PM10stations within the city. Model results are also validated by the MODIS aerosol optical depth (AOD), employing deep blue (DB) algorithms for aerosol loadings. Model validation included Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), equipped with the lidar instrument, to disclose the vertical structure of dust aerosols as well as aerosol subtypes. Promising results encourage further research and application of high-resolution modeling and satellite-based remote sensing to warn of approaching severe dust events and reduce risks for safety and health.
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Vukovic, A., M. Vujadinovic, G. Pejanovic, J. Andric, M. R. Kumjian, V. Djurdjevic, M. Dacic, et al. "Numerical simulation of "an American haboob"." Atmospheric Chemistry and Physics 14, no. 7 (April 2, 2014): 3211–30. http://dx.doi.org/10.5194/acp-14-3211-2014.
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Abstract. A dust storm of fearful proportions hit Phoenix in the early evening hours of 5 July 2011. This storm, an American haboob, was predicted hours in advance because numerical, land–atmosphere modeling, computing power and remote sensing of dust events have improved greatly over the past decade. High-resolution numerical models are required for accurate simulation of the small scales of the haboob process, with high velocity surface winds produced by strong convection and severe downbursts. Dust productive areas in this region consist mainly of agricultural fields, with soil surfaces disturbed by plowing and tracks of land in the high Sonoran Desert laid barren by ongoing draught. Model simulation of the 5 July 2011 dust storm uses the coupled atmospheric-dust model NMME–DREAM (Non-hydrostatic Mesoscale Model on E grid, Janjic et al., 2001; Dust REgional Atmospheric Model, Nickovic et al., 2001; Pérez et al., 2006) with 4 km horizontal resolution. A mask of the potentially dust productive regions is obtained from the land cover and the normalized difference vegetation index (NDVI) data from the Moderate Resolution Imaging Spectroradiometer (MODIS). The scope of this paper is validation of the dust model performance, and not use of the model as a tool to investigate mechanisms related to the storm. Results demonstrate the potential technical capacity and availability of the relevant data to build an operational system for dust storm forecasting as a part of a warning system. Model results are compared with radar and other satellite-based images and surface meteorological and PM10 observations. The atmospheric model successfully hindcasted the position of the front in space and time, with about 1 h late arrival in Phoenix. The dust model predicted the rapid uptake of dust and high values of dust concentration in the ensuing storm. South of Phoenix, over the closest source regions (~25 km), the model PM10 surface dust concentration reached ~2500 μg m−3, but underestimated the values measured by the PM10 stations within the city. Model results are also validated by the MODIS aerosol optical depth (AOD), employing deep blue (DB) algorithms for aerosol loadings. Model validation included Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), equipped with the lidar instrument, to disclose the vertical structure of dust aerosols as well as aerosol subtypes. Promising results encourage further research and application of high-resolution modeling and satellite-based remote sensing to warn of approaching severe dust events and reduce risks for safety and health.
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Peng, Y., K. von Salzen, and J. Li. "Simulation of mineral dust aerosol with Piecewise Log-normal Approximation (PLA) in CanAM4-PAM." Atmospheric Chemistry and Physics 12, no. 15 (August 1, 2012): 6891–914. http://dx.doi.org/10.5194/acp-12-6891-2012.
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Abstract. A new size-resolved dust scheme based on the numerical method of piecewise log-normal approximation (PLA) was developed and implemented in the fourth generation of the Canadian Atmospheric Global Climate Model with the PLA Aerosol Model (CanAM4-PAM). The total simulated annual global dust emission is 2500 Tg yr−1, and the dust mass load is 19.3 Tg for year 2000. Both are consistent with estimates from other models. Results from simulations are compared with multiple surface measurements near and away from dust source regions, validating the generation, transport and deposition of dust in the model. Most discrepancies between model results and surface measurements are due to unresolved aerosol processes. Biases in long-range transport are also contributing. Radiative properties of dust aerosol are derived from approximated parameters in two size modes using Mie theory. The simulated aerosol optical depth (AOD) is compared with satellite and surface remote sensing measurements and shows general agreement in terms of the dust distribution around sources. The model yields a dust AOD of 0.042 and dust aerosol direct radiative forcing (ADRF) of −1.24 W m−2 respectively, which show good consistency with model estimates from other studies.
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Xie, Xiaoning, Xiaodong Liu, Huizheng Che, Xiaoxun Xie, Xinzhou Li, Zhengguo Shi, Hongli Wang, Tianliang Zhao, and Yangang Liu. "Radiative feedbacks of dust in snow over eastern Asia in CAM4-BAM." Atmospheric Chemistry and Physics 18, no. 17 (August 31, 2018): 12683–98. http://dx.doi.org/10.5194/acp-18-12683-2018.
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Abstract. Dust in snow on the Tibetan Plateau (TP) could reduce the visible snow albedo by changing surface optical properties and removing the snow cover through increased snowmelt, which leads to a significant positive radiative forcing and remarkably alters the regional energy balance and the eastern Asian climate system. This study extends our previous investigation in dust–radiation interactions to investigate the dust-in-snow radiative forcing (SRF) and its feedbacks on the regional climate and the dust cycle over eastern Asia through the use of the Community Atmosphere Model version 4 with a Bulk Aerosol Model parameterizations of the dust size distribution (CAM4-BAM). Our results show that SRF increases the eastern Asian dust emissions significantly by 13.7 % in the spring, countering a 7.6 % decrease in the regional emissions by the dust direct radiative forcing (DRF). SRF also remarkably affects the whole dust cycle, including transport and deposition of dust aerosols over eastern Asia. The simulations indicate an increase in dust emissions of 5.1 %, due to the combined effect of DRF and SRF. Further analysis reveals that these results are mainly due to the regional climatic feedbacks induced by SRF over eastern Asia. By reducing the snow albedo over the TP, the dust in snow mainly warms the TP and influences its thermal effects by increasing the surface sensible and latent heat flux, which in turn increases the aridity and westerly winds over northwestern China and affects the regional dust cycle. Additionally, the dust in snow also accelerates the snow-melting process, reduces the snow cover and then expands the eastern Asian dust source region, which results in increasing the regional dust emissions. Hence, a significant feature of SRF on the TP is the creation of a positive feedback loop that affects the dust cycle over eastern Asia.
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Zamora, Lauren M., Ralph A. Kahn, Nikolaos Evangeliou, Christine D. Groot Zwaaftink, and Klaus B. Huebert. "Comparisons between the distributions of dust and combustion aerosols in MERRA-2, FLEXPART, and CALIPSO and implications for deposition freezing over wintertime Siberia." Atmospheric Chemistry and Physics 22, no. 18 (September 20, 2022): 12269–85. http://dx.doi.org/10.5194/acp-22-12269-2022.
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Abstract. Aerosol distributions have a potentially large influence on climate-relevant cloud properties but can be difficult to observe over the Arctic given pervasive cloudiness, long polar nights, data paucity over remote regions, and periodic diamond dust events that satellites can misclassify as aerosol. We compared Arctic 2008–2015 mineral dust and combustion aerosol distributions from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite, the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) reanalysis products, and the FLEXible PARTicle (FLEXPART) dispersion model. Based on coincident, seasonal Atmospheric Infrared Sounder (AIRS) Arctic satellite meteorological data, diamond dust may occur up to 60 % of the time in winter, but it hardly ever occurs in summer. In its absence, MERRA-2 and FLEXPART each predict the vertical and horizontal distribution of large-scale patterns in combustion aerosols with relatively high confidence (Kendall tau rank correlation > 0.6), although a sizable amount of variability is still unaccounted for. They do the same for dust, except in conditions conducive to diamond dust formation where CALIPSO is likely misclassifying diamond dust as mineral dust and near the surface (< ∼ 2 km) where FLEXPART may be overpredicting local dust emissions. Comparisons to ground data suggest that MERRA-2 Arctic dust concentrations can be improved by the addition of local dust sources. All three products predicted that wintertime dust and combustion aerosols occur most frequently over the same Siberian regions where diamond dust is most common in the winter. This suggests that dust aerosol impacts on ice phase processes may be particularly high over Siberia, although further wintertime model validation with non-CALIPSO observations is needed. This assessment paves the way for applying the model-based aerosol simulations to a range of regional-scale Arctic aerosol–cloud interaction studies with greater confidence.
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Wang, Jikang, Bihui Zhang, Hengde Zhang, Cong Hua, Linchang An, and Hailin Gui. "Simulation of a Severe Sand and Dust Storm Event in March 2021 in Northern China: Dust Emission Schemes Comparison and the Role of Gusty Wind." Atmosphere 13, no. 1 (January 10, 2022): 108. http://dx.doi.org/10.3390/atmos13010108.
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Northern China experienced a severe sand and dust storm (SDS) on 14/15 March 2021. It was difficult to simulate this severe SDS event accurately. This study compared the performances of three dust-emission schemes on simulating PM10 concentration during this SDS event by implementing three vertical dust flux parameterizations in the Comprehensive Air-Quality Model with Extensions (CAMx) model. Additionally, a statistical gusty-wind model was implemented in the dust-emission scheme, and it was used to quantify the gusty-wind contribution to dust emissions and peak PM10 concentration. As a result, the LS scheme (Lu and Shao 1999) produced the minimum errors for peak PM10 concentrations, the MB scheme (Marticorena and Bergametti 1995) underestimated the PM10 concentrations by 70–90%, and the KOK scheme (Kok et al. 2014) overestimated PM10 concentrations by 10–50% in most areas. The gusty-wind model could reasonably reproduce the probability density function of 2-min wind speeds. There were 5–40% more dust-emission flux and 5–40% more peak PM10 concentrations generated by the gusty wind than the hourly wind in the dust-source regions. The increase of peak PM10 concentration caused by gusty wind in the non-dust-source regions was higher than in the dust-source regions, with 10–50%. Implementing the gusty-wind model could help improve the LS scheme’s performance in simulating PM10 concentrations of this severe SDS event. More work is still needed to investigate the reliability of the gusty-wind model and LS scheme on various SDS events.
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Palacios-Peña, Laura, Juan P. Montávez, José M. López-Romero, Sonia Jerez, Juan J. Gómez-Navarro, Raquel Lorente-Plazas, Jesús Ruiz, and Pedro Jiménez-Guerrero. "Added Value of Aerosol-Cloud Interactions for Representing Aerosol Optical Depth in an Online Coupled Climate-Chemistry Model over Europe." Atmosphere 11, no. 4 (April 8, 2020): 360. http://dx.doi.org/10.3390/atmos11040360.
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Aerosol-cloud interactions (ACI) represent one of the most important sources of uncertainties in climate modelling. In this sense, realistic simulations of ACI are needed for a better understanding of the complex interactions between air pollution and the climate system. This work quantifies the added value of including ACI in an online coupled climate/chemistry model (WRF-Chem, 0.44 ∘ horizontal resolution, years 2003 to 2010) in order to assess whether there is an improvement in the representation of aerosol optical depth (AOD). Modelling results for each species have been evaluated against the Copernicus Atmosphere Monitoring Service (CAMS) reanalysis, and AOD at 675 nm has been compared to AERONET data. Results indicate that the improvements of the monthly biases are around 8% for total AOD550 when including ACI, reaching 20% for the monthly bias in AOD550 coming from dust. Moreover, the temporal representation of AOD550 largely improves (increase in the Pearson time correlation coefficients), ranging from 6% to 20% depending on the chemical species considered. The benefits from this improvement overcome the problems derived from the high computational time required in ACI simulations (eight times higher with respect to simulations not including aerosol-cloud interactions).
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Tollefsen, Dag, Paul van Walree, Trond Jenserud, and Vidar Forsmo. "Under-ice 4-8 kHz acoustic transmission and communication in ducted environments in the Arctic Ocean." Journal of the Acoustical Society of America 152, no. 4 (October 2022): A109. http://dx.doi.org/10.1121/10.0015708.
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Underwater communications and navigation for small platforms can typically involve acoustic systems operating at kHz frequencies. For under-ice applications, this motivates studies of acoustic transmission in present-day Arctic conditions. This paper presents data from recent mid-frequency (4–8 kHz) under-ice acoustic transmission and communication experiments to ∼10 km range in the Nansen Basin and in the Beaufort Sea of the Arctic Ocean. For shallow sources and receivers, delay profiles show early arrivals due to ducted paths followed by a group of strong arrivals due to bottom-interacting paths. The relative amplitudes of these groups depend on duct and under-ice properties. We demonstrate that despite shallow (∼25 m) source/receiver depths, good communication performance can be achieved in these single- and double-ducted environments by exploiting the bottom-interacting paths. Simulations with the Bellhop ray model support the findings.
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Lee, Y. H., K. Chen, and P. J. Adams. "Development of a global model of mineral dust aerosol microphysics." Atmospheric Chemistry and Physics Discussions 8, no. 6 (October 31, 2008): 18765–802. http://dx.doi.org/10.5194/acpd-8-18765-2008.
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Abstract. A mineral dust module is developed and implemented into the global aerosol microphysics model, GISS-TOMAS. The model is evaluated against long-term measurements of dust surface mass concentrations and deposition fluxes. Predicted mass concentrations and deposition fluxes are in error on average by a factor of 3 and 5, respectively. The comparison shows that the model performs better near the dust source regions but underestimates surface concentrations and deposition fluxes in more remote regions. For example, including only sites with measured dust concentrations of at least 0.5 μg m−3, the model prediction agrees with observations to within a factor of 2. It was hypothesized that the lifetime of dust, 2.6 days in our base case, is too short and causes the underestimation in remote areas. However, a sensitivity simulation with smaller dust particles and increased lifetime, 3.7 days, does not significantly improve the comparison. We conclude that the underestimation of mineral dust in remote areas results from local factors and sources not well described by the dust source function and/or the GCM meteorology. The effect of dust aerosols on CCN(0.2%) concentrations is negligible in most regions of the globe; however, CCN(0.2%) concentrations decrease by 10–20% in dusty regions as a result of coagulational scavenging of CCN particles by dust and a decrease in H2SO4 condensation to CCN particles due to the additional surface area of dust.
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Poppe, A. R. "The contribution of Centaur-emitted dust to the interplanetary dust distribution." Monthly Notices of the Royal Astronomical Society 490, no. 2 (October 9, 2019): 2421–29. http://dx.doi.org/10.1093/mnras/stz2800.
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ABSTRACT Interplanetary dust grains originate from a variety of source bodies, including comets, asteroids, and Edgeworth–Kuiper belt objects. Centaurs, generally defined as those objects with orbits that cross the outer planets, have occasionally been observed to exhibit cometary-like outgassing at distances beyond Jupiter, implying that they may be an important source of dust grains in the outer Solar system. Here, we use an interplanetary dust grain dynamics model to study the behaviour and equilibrium distribution of Centaur-emitted interplanetary dust grains. We focus on the five Centaurs with the highest current mass-loss rates: 29P/Schwassmann-Wachmann 1, 166P/2001 T4, 174P/Echeclus, C/2001 M10, and P/2004 A1, which together comprise 98 per cent of the current mass loss from all Centaurs. Our simulations show that Centaur-emitted dust grains with radii s < 2 μm have median lifetimes consistent with Poynting–Robertson (P–R) drag lifetimes, while grains with radii s > 2 μm have median lifetimes much shorter than their P–R drag lifetimes, suggesting that dynamical interactions with the outer planets are effective in scattering larger grains, in analogy to the relatively short lifetimes of Centaurs themselves. Equilibrium density distributions of grains emitted from specific Centaurs show a variety of structure including local maxima in the outer Solar system and azimuthal asymmetries, depending on the orbital elements of the parent Centaur. Finally, we compare the total Centaur interplanetary dust density to dust produced from Edgeworth–Kuiper belt objects, Jupiter-family comets, and Oort cloud comets, and conclude that Centaur-emitted dust may be an important component between 5 and 15 au, contributing approximately 25 per cent of the local interplanetary dust density at Saturn.
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Pavel, Amosov, Baklanov Alexander, Makarov Dmitriy, and Masloboev Vladimir. "Estimating air pollution levels by numerical simulation depending on wind flow speed and dust source area." Izvestiya vysshikh uchebnykh zavedenii Gornyi zhurnal, no. 5 (August 6, 2020): 80–89. http://dx.doi.org/10.21440/0536-1028-2020-5-80-89.
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Research aim is to estimate atmospheric pollution levels in the town of Apatity, by numerical simulation, depending on the discrete arrangement of dust sources at the tailing dump closest to the town and the speed of wind flow. Methodology. For computer 3D modeling, the COMSOL software was used. To calculate the aerodynamic properties the approach of incompressible fluid and standard (k–ε)-model of turbulence were used. The spread of dust pollution has been modeled by numerically solving the convective-diffusion equation of impurity transfer taking into account the deposition rate. Numerical experiments were performed for wind flow speeds between 5 and 23 m/s and a discrete representation of the dust source area between 2 and 10 ha. Results. The spatial distributions of the model's aerodynamic properties and the interval (and total) distributions of dust pollution were obtained. The Starye Apatity area is most exposed to atmospheric pollution. Atmospheric pollution levels were analyzed and generalized to functional dependencies, depending on the values of the model's variable parameters. It is shown that the calculated dependencies between the maximum dust concentration and the dust source area can be described by linear functions, which allows predicting the critical dust source area, at which the level of air pollution reaches the threshold limit value. It is demonstrated that the dependence of the maximum dust concentration on wind flow speed at fixed dust source area values can be approximated by a power-law function. Summary. A generalized analytical formula has been derived that allows predicting maximum dust concentrations in the town of Apatity depending on the discrete locations of dust sources at the tailing dump and the speed of wind flow.
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Reader, M. C., I. Fung, and N. McFarlane. "Mineral aerosols: a comparison of the last glacial maximum and preindustrial Holocene." Canadian Journal of Earth Sciences 37, no. 5 (May 1, 2000): 751–67. http://dx.doi.org/10.1139/e99-109.
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A passive mineral dust aerosol model based on source strengths deduced from polar ice core dust concentrations is introduced into the Canadian Centre for Climate Modelling and Analysis (CCCma) second-generation atmospheric general circulation model (GCMII) and used to compare features of the fine particle mineral dust aerosol in a last glacial maximum (LGM) simulation to those of a preindustrial Holocene (MOD) dust simulation. The resulting dust optical thickness is 8-16 times greater over most of the globe during the LGM. The model displays several seasonal characteristics observed in present-day satellite observations of dust, such as the summer maximum over the Arabian Sea and the seasonal north-south shift of the Sahara-Sahel plume. Both of these features are also present in the LGM simulation, though there are some noticeable differences in seasonal variation of dust between the last glacial maximum and the preindustrial Holocene. Since the simulated dust lifetimes are very similar for the MOD and LGM climates, it seems that increased LGM dust lifetime is not the major reason for the observed increase in dust concentration in polar ice cores during the LGM relative to the present.
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Jin, Jianbing, Arjo Segers, Hong Liao, Arnold Heemink, Richard Kranenburg, and Hai Xiang Lin. "Source backtracking for dust storm emission inversion using an adjoint method: case study of Northeast China." Atmospheric Chemistry and Physics 20, no. 23 (December 8, 2020): 15207–25. http://dx.doi.org/10.5194/acp-20-15207-2020.
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Abstract. Emission inversion using data assimilation fundamentally relies on having the correct assumptions about the emission background error covariance. A perfect covariance accounts for the uncertainty based on prior knowledge and is able to explain differences between model simulations and observations. In practice, emission uncertainties are constructed empirically; hence, a partially unrepresentative covariance is unavoidable. Concerning its complex parameterization, dust emissions are a typical example where the uncertainty could be induced from many underlying inputs, e.g., information on soil composition and moisture, land cover and erosive wind velocity, and these can hardly be taken into account together. This paper describes how an adjoint model can be used to detect errors in the emission uncertainty assumptions. This adjoint-based sensitivity method could serve as a supplement of a data assimilation inverse modeling system to trace back the error sources in case large observation-minus-simulation residues remain after assimilation based on empirical background covariance. The method follows an application of a data assimilation emission inversion for an extreme severe dust storm over East Asia (Jin et al., 2019b). The assimilation system successfully resolved observation-minus-simulation errors using satellite AOD observations in most of the dust-affected regions. However, a large underestimation of dust in Northeast China remained despite the fact that the assimilated measurements indicated severe dust plumes there. An adjoint implementation of our dust simulation model is then used to detect the most likely source region for these unresolved dust loads. The backward modeling points to the Horqin desert as the source region, which was indicated as a non-source region by the existing emission scheme. The reference emission and uncertainty are then reconstructed over the Horqin desert by assuming higher surface erodibility. After the emission reconstruction, the emission inversion is performed again, and the posterior dust simulations and reality are now in much closer harmony. Based on our results, it is advised that emission sources in dust transport models include the Horqin desert as a more active source region.
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Lee, Y. H., K. Chen, and P. J. Adams. "Development of a global model of mineral dust aerosol microphysics." Atmospheric Chemistry and Physics 9, no. 7 (April 3, 2009): 2441–58. http://dx.doi.org/10.5194/acp-9-2441-2009.
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Abstract. A mineral dust module is developed and implemented into the global aerosol microphysics model, GISS-TOMAS. The model is evaluated against long-term measurements of dust surface mass concentrations and deposition fluxes. Predicted mass concentrations and deposition fluxes are in error on average by a factor of 3 and 5, respectively. The comparison shows that the model performs better near the dust source regions but underestimates surface concentrations and deposition fluxes in more remote regions. Including only sites with measured dust concentrations of at least 0.5 μg m−3, the model prediction agrees with observations to within a factor of 2. It was hypothesized that the lifetime of dust, 2.6 days in our base case, is too short and causes the underestimation in remote areas. However, a sensitivity simulation with smaller dust particles and increased lifetime, 3.7 days, does not significantly improve the comparison. These results suggest that the underestimation of mineral dust in remote areas may result from local factors/sources not well described by the global dust source function used here or the GCM meteorology. The effect of dust aerosols on CCN(0.2%) concentrations is negligible in most regions of the globe; however, CCN(0.2%) concentrations change decrease by 10–20% in dusty regions the impact of dust on CCN(0.2%) concentrations in dusty regions is very sensitive to the assumed size distribution of emissions. If emissions are predominantly in the coarse mode, CCN(0.2%) decreases in dusty regions up to 10–20% because dust competes for condensable H2SO4, reducing the condensational growth of ultrafine mode particles to CCN sizes. With significant fine mode emissions, however, CCN(0.2%) doubles in Saharan source regions because the direct emission of dust particles outweighs any microphysical feedbacks. The impact of dust on CCN concentrations active at various water supersaturations is also investigated. Below 0.1%, CCN concentrations increase significantly in dusty regions due to the presence of coarse dust particles. Above 0.2%, CCN concentrations show a similar behavior as CCN(0.2%).
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Peng, Y., K. von Salzen, and J. Li. "Simulation of mineral dust aerosol with piecewise log-normal approximation (PLA) in CanAM4-PAM." Atmospheric Chemistry and Physics Discussions 11, no. 9 (September 22, 2011): 26477–520. http://dx.doi.org/10.5194/acpd-11-26477-2011.
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Abstract. A new size-resolved dust scheme based on the numerical method of piecewise log-normal approximation (PLA) was developed and implemented in the fourth generation of the Canadian Atmospheric Global Climate Model with the PLA Aerosol Module (CanAM4-PAM). The total simulated annual mean dust burden is 37.8 mg m−2 for year 2000, which is consistent with estimates from other models. Results from simulations are compared with multiple surface measurements near and away from dust source regions, validating the generation, transport and deposition of dust in the model. Most discrepancies between model results and surface measurements are due to unresolved aerosol processes. Radiative properties of dust aerosol are derived from approximated parameters in two size modes using Mie theory. The simulated aerosol optical depth (AOD) is compared with several satellite observations and shows good agreements. The model yields a dust AOD of 0.042 and total AOD of 0.126 for the year 2000. The simulated aerosol direct radiative forcings (ADRF) of dust and total aerosol over ocean are −1.24 W m−2 and −4.76 W m−2 respectively, which show good consistency with satellite estimates for the year 2001.
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Zhang, Fei Fan, Hua Yong Zhang, and Tou Sheng Huang. "Dynamics on the Interaction between Vegetation Growth and Aeolian Dust Deposition." Advanced Materials Research 356-360 (October 2011): 2430–33. http://dx.doi.org/10.4028/www.scientific.net/amr.356-360.2430.
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From the holistic perspective, a new dynamic model is proposed in this research to investigate the interaction between vegetation growth and aeolian dust deposition. Three cases of equilibrium distribution can be obtained and the stability of interior equilibriums is determined. When there is a stable interior equilibrium, a critical curve exists and separates the coexistent area where vegetation can survive in the environment of aeolian dust deposition, from the other area where vegetation is to be excluded. Simulation analysis further reveals the variation of the critical curve with the parameters and the anthropic influences. The critical curve and the coexistent equilibrium described by the model may be used as a theoretical basis to evaluate the feasibility of vegetation restoration in the environment of aeolian dust deposition.
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Dong, X., J. S. Fu, K. Huang, and D. Tong. "Model development of dust emission and heterogeneous chemistry within the Community Multiscale Air Quality modeling system and its application over East Asia." Atmospheric Chemistry and Physics Discussions 15, no. 24 (December 17, 2015): 35591–643. http://dx.doi.org/10.5194/acpd-15-35591-2015.
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Abstract. The Community Multiscale Air Quality (CMAQ) model has been further developed in terms of simulating natural wind-blown dust in this study, with a series of modifications aimed at improving the model's capability to predict the emission, transport, and chemical reactions of dust aerosols. The default parameterization of threshold friction velocity constants in the CMAQ are revised to avoid double counting of the impact of soil moisture based on the re-analysis of field experiment data; source-dependent speciation profiles for dust emission are derived based on local measurements for the Gobi and Taklamakan deserts in East Asia; and dust heterogeneous chemistry is implemented to simulate the reactions involving dust aerosol. The improved dust module in the CMAQ was applied over East Asia for March and April from 2006 to 2010. Evaluation against observations has demonstrated that simulation bias of PM10 and aerosol optical depth (AOD) is reduced from −55.42 and −31.97 % in the original CMAQ to −16.05 and −22.1 % in the revised CMAQ, respectively. Comparison with observations at the nearby Gobi stations of Duolun and Yulin indicates that applying a source-dependent profile helps reduce simulation bias for trace metals. Implementing heterogeneous chemistry is also found to result in better agreement with observations for sulfur dioxide (SO2), sulfate (SO42-), nitric acid (HNO3), nitrous oxides (NOx), and nitrate (NO3-). Investigation of a severe dust storm episode from 19 to 21 March 2010 suggests that the revised CMAQ is capable of capturing the spatial distribution and temporal variations of dust aerosols. Model evaluation indicates potential uncertainties within the excessive soil moisture fraction used by meteorological simulation. The mass contribution of fine mode aerosol in dust emission may be underestimated by 50 %. The revised revised CMAQ provides a useful tool for future studies to investigate the emission, transport, and impact of wind-blown dust over East Asia and elsewhere.
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Castellanos-Ramírez, A., A. Rodríguez-González, Z. Meliani, P. R. Rivera-Ortiz, A. C. Raga, and J. Cantó. "Two-wind interactions in binaries with two orbiting giant stars." Monthly Notices of the Royal Astronomical Society 507, no. 3 (August 19, 2021): 4044–52. http://dx.doi.org/10.1093/mnras/stab2373.
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ABSTRACT Some red giant envelopes present spiral structures (seen either in dust-scattered stellar continuum or in molecular line emission), the most striking example probably being AFGL 3068. This object has been modeled (both analytically and numerically) in terms of a wind ejected from a star in orbit around a binary companion. We revisit both analytical models and 3D simulations of a wind from an orbiting red giant star, and extend the numerical simulations to the case of a binary with two red giants with strong winds. We find that most two-wind models on the orbital plane show a ‘double spiral’ structure close to the binary source, and that these two arms merge into a single spiral structure at larger distances. However, for the case of a binary with two identical winds, the two spiral arms are still present at large distances from the binary source. We also find that for models of two (not identical) dynamically important winds, a region close to the orbital plane has material from both winds. Also, an approximately conical region centered on the orbital axis is filled exclusively by the wind with larger momentum rate. These two structures lead to morphologies reminiscent of the so-called ‘hour glass’ planetary nebulae. Finally, we find that increasing wind velocity disparities lead to the formation of clumpy structures along the spiral arms. Observations of ‘clumpy spirals’ are therefore likely to indicate the presence of two strong winds from the stars in the central binary system.
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Dong, Xinyi, Joshua S. Fu, Kan Huang, Daniel Tong, and Guoshun Zhuang. "Model development of dust emission and heterogeneous chemistry within the Community Multiscale Air Quality modeling system and its application over East Asia." Atmospheric Chemistry and Physics 16, no. 13 (July 6, 2016): 8157–80. http://dx.doi.org/10.5194/acp-16-8157-2016.
Full textAbstract:
Abstract. The Community Multiscale Air Quality (CMAQ) model has been further developed in terms of simulating natural wind-blown dust in this study, with a series of modifications aimed at improving the model's capability to predict the emission, transport, and chemical reactions of dust. The default parameterization of initial threshold friction velocity constants are revised to correct the double counting of the impact of soil moisture in CMAQ by the reanalysis of field experiment data; source-dependent speciation profiles for dust emission are derived based on local measurements for the Gobi and Taklamakan deserts in East Asia; and dust heterogeneous chemistry is also implemented. The improved dust module in the CMAQ is applied over East Asia for March and April from 2006 to 2010. The model evaluation result shows that the simulation bias of PM10 and aerosol optical depth (AOD) is reduced, respectively, from −55.42 and −31.97 % by the original CMAQ to −16.05 and −22.1 % by the revised CMAQ. Comparison with observations at the nearby Gobi stations of Duolun and Yulin indicates that applying a source-dependent profile helps reduce simulation bias for trace metals. Implementing heterogeneous chemistry also results in better agreement with observations for sulfur dioxide (SO2), sulfate (SO42−), nitric acid (HNO3), nitrous oxides (NOx), and nitrate (NO3−). The investigation of a severe dust storm episode from 19 to 21 March 2010 suggests that the revised CMAQ is capable of capturing the spatial distribution and temporal variation of dust. The model evaluation also indicates potential uncertainty within the excessive soil moisture used by meteorological simulation. The mass contribution of fine-mode particles in dust emission may be underestimated by 50 %. The revised CMAQ model provides a useful tool for future studies to investigate the emission, transport, and impact of wind-blown dust over East Asia and elsewhere.
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Soleimani Sardoo, Farshad, Tayyebeh Mesbahzadeh, Ali Salajeghe, Gholamreza Zehtabian, Abbas Ranjbar, Mario Marcello Miglietta, and Nir Krakauer. "Antecedent Soil Moisture Conditions Influenced Vertical Dust Flux: A Case Study in Iran Using WRF-Chem Model." Land 11, no. 6 (May 31, 2022): 819. http://dx.doi.org/10.3390/land11060819.
Full textAbstract:
Soil moisture is one of the most important parameters affecting dust emission flux. This study was conducted to investigate the effects of soil moisture on vertical dust flux in the central plateau region of Iran. In this study, the WRF-Chem (Weather Research and Forecast with Chemistry) model, with the GOCART (Global Ozone Chemistry Aerosol Radiation and Transport) scheme, was used to estimate the dust emission flux during a major storm from 19 to 21 July 2015, and to discriminate between dust sources. The results showed that the Kyrgyz deserts in Turkmenistan, the Arabian deserts in Saudi Arabia, the deserts of Iraq, and the Helmand region in Afghanistan are sources of foreign dust. Additionally, the central desert plain was identified as an internal dust source, where the dust level reached 7000 µg m−2 s−1. The results of WRF-Chem simulation were verified with reanalysis data from MERRA2 and AERONET data from Natanz station, which showed good agreement with the simulation. Based on the GLDAS reanalysis, soil moisture content varied between 2.6% and 34%. Linear and nonlinear regression of vertical dust flux values and soil moisture showed nonlinear behavior following the exponential function, with a correlation coefficient of 0.8 and a strong negative association between soil moisture and vertical dust flux.