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Journal articles on the topic 'Radiative simulation'
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1
Guseva, A. A., and I. S. Grigor’Ev. "Mathematical simulation of aircraft engine jet exhausts radiation." Journal of «Almaz – Antey» Air and Space Defence Corporation, no. 4 (December 30, 2018): 30–36. http://dx.doi.org/10.38013/2542-0542-2018-4-30-36.
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The paper deals with the problems of mathematical simulation of aircraft engine jet exhausts radiation, the simulation being carried out by means of shader subroutines for the concurrent computation of the radiative transfer equation on the video card resources. The combination of an analytical model of an isobaric jet and ray tracing of computation of the radiative transfer equation allows us to develop a flexible model of aircraft jet radiation, the model taking into account the main parameters of streams in the jet and in the co-current flow, the spectral lines of the radiating components, and provides real-time computation. For the graphic implementation of the model, the OpenGL standard is used
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Henrion, Lucca, Michael C. Gross, Sebastian Ferreryo Fernandez, Chandan Paul, Samuel Kazmouz, Volker Sick, and Daniel C. Haworth. "Characterization of radiative heat transfer in a spark-ignition engine through high-speed experiments and simulations." Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles 74 (2019): 61. http://dx.doi.org/10.2516/ogst/2019030.
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A combined experimental and Large-Eddy Simulation (LES) study of molecular radiation is presented for combustion in a homogeneous pre-mixed spark-ignition engine. Molecular radiation can account for ~10% of the engine heat loss and could have a noticeable impact on the local conditions within the combustion chamber. The Transparent Combustion Chamber (TCC) engine, a single-cylinder two-valve research engine with a transparent liner and piston for optical access, was used for this study. High-speed infrared emission spectroscopy and radiative post-processing of LES calculations have been performed to gain insight into the timescales and magnitude of radiative emissions of molecular gases during the combustion process. Both the measurements and simulations show significant Cycle-to-Cycle Variations (CCV) of radiative emission. There is agreement in the instantaneous radiative spectrum of experiment and simulation, but the crank-angle development of the radiative spectrum shows disagreement. The strengths and limitations of the optical experiments and radiative simulations are seen in the results and suggest pathways for future efforts in characterizing the influence of molecular radiation. In particular, focusing on the relative changes of the spectral features will be important as they contain information about the thermochemical properties of the gas mixture.
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Shi, Xiangjun, Chunhan Li, Lijuan Li, Wentao Zhang, and Jiaojiao Liu. "Estimating the CMIP6 Anthropogenic Aerosol Radiative Effects with the Advantage of Prescribed Aerosol Forcing." Atmosphere 12, no. 3 (March 21, 2021): 406. http://dx.doi.org/10.3390/atmos12030406.
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The prescribed anthropogenic aerosol forcing recommended by Coupled Model Intercomparison Project Phase 6 (CMIP6) was implemented in an atmospheric model. With the reduced complexity of anthropogenic aerosol forcing, each component of anthropogenic aerosol effective radiative forcing (ERF) can be estimated by one or more calculation methods, especially for instantaneous radiative forcing (RF) from aerosol–radiation interactions (RFari) and aerosol–cloud interactions (RFaci). Simulation results show that the choice of calculation method might impact the magnitude and reliability of RFari. The RFaci—calculated by double radiation calls—is the definition-based Twomey effect, which previously was impossible to diagnose using the default model with physically based aerosol–cloud interactions. The RFari and RFaci determined from present-day simulations are very robust and can be used as offline simulation results. The robust RFari, RFaci, and corresponding radiative forcing efficiencies (i.e., the impact of environmental properties) are very useful for analyzing anthropogenic aerosol radiative effects. For instance, from 1975 to 2000, both RFari and RFaci showed a clear response to the spatial change of anthropogenic aerosol. The global average RF (RFari + RFaci) has enhanced (more negative) by ~6%, even with a slight decrease in the global average anthropogenic aerosol, and this can be explained by the spatial pattern of radiative forcing efficiency.
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Mashayekhi, R., P. Irannejad, J. Feichter, and A. A. Bidokhti. "Implementation of a new aerosol HAM model within the Weather Research and Forecasting (WRF) modeling system." Geoscientific Model Development Discussions 2, no. 2 (July 1, 2009): 681–707. http://dx.doi.org/10.5194/gmdd-2-681-2009.
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Abstract. A new coupled system of aerosol HAM model and the Weather, Research and Forecasting (WRF) model is presented in this paper. Unlike the current aerosol schemes used in WRF model, the HAM is using a "pseudomodal" approach for the representation of the particle size distribution. The aerosol components considered are sulfate, black carbon, particulate organic matter, sea salt and mineral dust. The preliminary model results are presented for two different 6-day simulation periods from 22 to 28 February 2006 as a winter period and 6 to 12 May 2006 as a mild period. The mean shortwave radiation and thermal forcing were calculated from the model simulations with and without aerosols feedback for two simulation periods. A negative radiative forcing and cooling of the atmosphere were found mainly over the regions of high emission of mineral dust. The absorption of shortwave radiation by black carbon caused warming effects in some regions with positive radiative forcing. The simulated daily mean sulfate mass concentration showed a rather good agreement with the measurements in the European EMEP network. The diurnal variation of the simulated hourly PM10 mass concentration at Tehran was also qualitatively close to the observations in both simulation periods. The model captured diurnal cycle and the magnitude of the observed PM10 concentration during most of the simulation periods. The differences between the observed and simulated PM10 concentration resulted mostly from limitation of the model in simulating the clouds and precipitation, transport errors and uncertainties in the particulate emission rates. The inclusion of aerosols feedback in shortwave radiation scheme improved the simulated daily mean shortwave radiation fluxes in Tehran for both simulation periods.
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Markowski, Paul M., and Jerry Y. Harrington. "A Simulation of a Supercell Thunderstorm with Emulated Radiative Cooling beneath the Anvil." Journal of the Atmospheric Sciences 62, no. 7 (July 1, 2005): 2607–17. http://dx.doi.org/10.1175/jas3497.1.
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Abstract This note reports the preliminary results of an ongoing numerical study designed to investigate what effects, if any, radiative transfer processes can have on the evolution of convective storms. A pair of idealized three-dimensional simulations are conducted to demonstrate the potential dynamical importance of shortwave radiation reductions within the large shadows cast by storms. One of the simulations (the control) is run without surface physics and radiation. In the other simulation, radiative cooling due to cloud shading is emulated by prescribing a cooling rate to the skin temperature at any grid point at which cloud water was present overhead. The imposed skin cooling rate is consistent with past observations. Low-level air temperatures are coupled to the skin cooling in this second simulation by the inclusion of surface sensible heat fluxes using simple bulk aerodynamic drag laws (latent and soil heat fluxes are not included). Significant differences are observed between the two simulated storms, particularly in the evolution of the vertical vorticity field and gust fronts. The storm simulated with emulated cloud shading develops substantially weaker low-level rotation than the storm in the control simulation.
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Mechem, David B., Yefim L. Kogan, Mikhail Ovtchinnikov, Anthony B. Davis, K. Franklin Evans, and Robert G. Ellingson. "Multidimensional Longwave Forcing of Boundary Layer Cloud Systems." Journal of the Atmospheric Sciences 65, no. 12 (December 1, 2008): 3963–77. http://dx.doi.org/10.1175/2008jas2733.1.
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Abstract The importance of multidimensional (MD) longwave radiative effects on cloud dynamics is evaluated in an eddy-resolving model (ERM)—the two-dimensional analog to large-eddy simulation (LES)—framework employing multidimensional radiative transfer [Spherical Harmonics Discrete Ordinate Method (SHDOM)]. Simulations are performed for a case of unbroken, marine boundary layer stratocumulus and a broken field of trade cumulus. “Snapshot” calculations of MD and independent pixel approximation (IPA; 1D) radiative transfer applied to simulated cloud fields show that the total radiative forcing changes only slightly, although the MD effects significantly modify the spatial structure of the radiative forcing. Simulations of each cloud type employing MD and IPA radiative transfer, however, differ little. For the solid cloud case, relative to using IPA, the MD simulation exhibits a slight reduction in entrainment rate and boundary layer total kinetic energy (TKE) relative to the IPA simulation. This reduction is consistent with both the slight decrease in net radiative forcing and a negative correlation between local vertical velocity and radiative forcing, which implies a damping of boundary layer eddies. Snapshot calculations of the broken cloud case suggest a slight increase in radiative cooling, although few systematic differences are noted in the interactive simulations. This result is attributed to the fact that radiative cooling is a relatively minor contribution to the total energetics. For the cloud systems in this study, the use of IPA longwave radiative transfer is sufficiently accurate to capture the dynamical behavior of boundary layer clouds. Further investigations are required to generalize this conclusion for other cloud types and longer time integrations.
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Baró, Rocío, Laura Palacios-Peña, Alexander Baklanov, Alessandra Balzarini, Dominik Brunner, Renate Forkel, Marcus Hirtl, et al. "Regional effects of atmospheric aerosols on temperature: an evaluation of an ensemble of online coupled models." Atmospheric Chemistry and Physics 17, no. 15 (August 11, 2017): 9677–96. http://dx.doi.org/10.5194/acp-17-9677-2017.
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Abstract. The climate effect of atmospheric aerosols is associated with their influence on the radiative budget of the Earth due to the direct aerosol–radiation interactions (ARIs) and indirect effects, resulting from aerosol–cloud–radiation interactions (ACIs). Online coupled meteorology–chemistry models permit the description of these effects on the basis of simulated atmospheric aerosol concentrations, although there is still some uncertainty associated with the use of these models. Thus, the objective of this work is to assess whether the inclusion of atmospheric aerosol radiative feedbacks of an ensemble of online coupled models improves the simulation results for maximum, mean and minimum temperature at 2 m over Europe. The evaluated models outputs originate from EuMetChem COST Action ES1004 simulations for Europe, differing in the inclusion (or omission) of ARI and ACI in the various models. The cases studies cover two important atmospheric aerosol episodes over Europe in the year 2010: (i) a heat wave event and a forest fire episode (July–August 2010) and (ii) a more humid episode including a Saharan desert dust outbreak in October 2010. The simulation results are evaluated against observational data from the E-OBS gridded database. The results indicate that, although there is only a slight improvement in the bias of the simulation results when including the radiative feedbacks, the spatiotemporal variability and correlation coefficients are improved for the cases under study when atmospheric aerosol radiative effects are included.
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Ma, Xu, Tiejun Wang, and Lei Lu. "A Refined Four-Stream Radiative Transfer Model for Row-Planted Crops." Remote Sensing 12, no. 8 (April 18, 2020): 1290. http://dx.doi.org/10.3390/rs12081290.
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In modeling the canopy reflectance of row-planted crops, neglecting horizontal radiative transfer may lead to an inaccurate representation of vegetation energy balance and further cause uncertainty in the simulation of canopy reflectance at larger viewing zenith angles. To reduce this systematic deviation, here we refined the four-stream radiative transfer equations by considering horizontal radiation through the lateral “walls”, considered the radiative transfer between rows, then proposed a modified four-stream (MFS) radiative transfer model using single and multiple scattering. We validated the MFS model using both computer simulations and in situ measurements, and found that the MFS model can be used to simulate crop canopy reflectance at different growth stages with an accuracy comparable to the computer simulations (RMSE < 0.002 in the red band, RMSE < 0.019 in NIR band). Moreover, the MFS model can be successfully used to simulate the reflectance of continuous (RMSE = 0.012) and row crop canopies (RMSE < 0.023), and therefore addressed the large viewing zenith angle problems in the previous row model based on four-stream radiative transfer equations. Our results demonstrate that horizontal radiation is an important factor that needs to be considered in modeling the canopy reflectance of row-planted crops. Hence, the refined four-stream radiative transfer model is applicable to the real world.
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Yamaguchi, Takanobu, and David A. Randall. "Cooling of Entrained Parcels in a Large-Eddy Simulation." Journal of the Atmospheric Sciences 69, no. 3 (March 1, 2012): 1118–36. http://dx.doi.org/10.1175/jas-d-11-080.1.
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Abstract The relative importance, for cloud-top entrainment, of the cooling rates due to longwave radiation, evaporation, and mixing was assessed through analysis of the results produced by a Lagrangian parcel-tracking model (LPTM) incorporated into a large-eddy simulation model. The LPTM predicts each parcel’s trajectory over time, using the resolved velocity simulated by the host model. An LPTM makes it possible to identify entrained parcels; this is almost impossible to do in an observational study. A nocturnal stratocumulus cloud was simulated over 4h using a 5-m horizontal grid spacing and a 2.5-m vertical grid spacing. At the start of the last hour of the simulation, over 40 million parcels were placed near the top of the inversion layer and then tracked. Parcel histories were analyzed to identify entrained parcels. Entrainment occurs in cloud holes, which occur in dry regions of sinking air. Entrainment into the mixed layer is regulated by buoyancy, which requires parcels to be precooled in the inversion layer, prior to entrainment. A mixing fraction analysis was used to separate the cooling due to longwave radiation, evaporation, and mixing. Results show that radiative and evaporative cooling are of comparable importance, but that mixing is by far the dominant cooling mechanism. The radiative cooling rate is strongly inhomogeneous, and only weak radiative cooling is found in regions of entrainment. Therefore, the entrained parcels experience less than the horizontal-mean radiative cooling. Although radiative cooling maintains the boundary layer turbulence, its direct effect on buoyancy of entrained parcels is modest.
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Shang, J. S., and S. T. Surzhikov. "Nonequilibrium radiative hypersonic flow simulation." Progress in Aerospace Sciences 53 (August 2012): 46–65. http://dx.doi.org/10.1016/j.paerosci.2012.02.003.
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Yi, Hong-Liang, Subhash C. Mishra, Yong Huang, Qun-Zhi Zhu, Pedro Coelho, and Denis Lemonnier. "Numerical Simulation of Radiative Transfer." Mathematical Problems in Engineering 2015 (2015): 1–2. http://dx.doi.org/10.1155/2015/827042.
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Pincus, Robert, Piers M. Forster, and Bjorn Stevens. "The Radiative Forcing Model Intercomparison Project (RFMIP): experimental protocol for CMIP6." Geoscientific Model Development 9, no. 9 (September 27, 2016): 3447–60. http://dx.doi.org/10.5194/gmd-9-3447-2016.
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Abstract. The phrasing of the first of three questions motivating CMIP6 – “How does the Earth system respond to forcing?” – suggests that forcing is always well-known, yet the radiative forcing to which this question refers has historically been uncertain in coordinated experiments even as understanding of how best to infer radiative forcing has evolved. The Radiative Forcing Model Intercomparison Project (RFMIP) endorsed by CMIP6 seeks to provide a foundation for answering the question through three related activities: (i) accurate characterization of the effective radiative forcing relative to a near-preindustrial baseline and careful diagnosis of the components of this forcing; (ii) assessment of the absolute accuracy of clear-sky radiative transfer parameterizations against reference models on the global scales relevant for climate modeling; and (iii) identification of robust model responses to tightly specified aerosol radiative forcing from 1850 to present. Complete characterization of effective radiative forcing can be accomplished with 180 years (Tier 1) of atmosphere-only simulation using a sea-surface temperature and sea ice concentration climatology derived from the host model's preindustrial control simulation. Assessment of parameterization error requires trivial amounts of computation but the development of small amounts of infrastructure: new, spectrally detailed diagnostic output requested as two snapshots at present-day and preindustrial conditions, and results from the model's radiation code applied to specified atmospheric conditions. The search for robust responses to aerosol changes relies on the CMIP6 specification of anthropogenic aerosol properties; models using this specification can contribute to RFMIP with no additional simulation, while those using a full aerosol model are requested to perform at least one and up to four 165-year coupled ocean–atmosphere simulations at Tier 1.
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Saleeby, Stephen M., Susan C. van den Heever, Jennie Bukowski, Annette L. Walker, Jeremy E. Solbrig, Samuel A. Atwood, Qijing Bian, et al. "The influence of simulated surface dust lofting and atmospheric loading on radiative forcing." Atmospheric Chemistry and Physics 19, no. 15 (August 14, 2019): 10279–301. http://dx.doi.org/10.5194/acp-19-10279-2019.
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Abstract. This high-resolution numerical modeling study investigates the potential range of impact of surface-lofted dust aerosols on the mean radiative fluxes and temperature changes associated with a dust-lofting episode over the Arabian Peninsula (2–5 August 2016). Assessing the potential for lofted dust to impact the radiation budget and temperature response in regions of the world that are prone to intense dust storms is important due to the impact of such temperature perturbations on thermally driven mesoscale circulations such as sea breezes and convective outflows. As such, sensitivity simulations using various specifications of the dust-erodible fraction were performed using two high-resolution mesoscale models that use similar dust-lofting physics based on threshold friction wind velocity and soil characteristics. The dust-erodible fraction, which represents the fraction (0.0 to 1.0) of surface soil that could be mechanically lifted by the wind and controls the location and magnitude of surface dust flux, was varied for three experiments with each model. The “Idealized” experiments, which used an erodible fraction of 1.0 over all land grid cells, represent the upper limit on dust lofting within each modeling framework, the “Ginoux” experiments used a 1∘ resolution, spatially varying erodible fraction dataset based on topographic depressions, and the “Walker” experiments used satellite-identified, 1 km resolution data with known lofting locations given an erodible fraction of 1.0. These simulations were compared with a “No-Dust” experiment in which no dust aerosols were permitted. The use of erodible fraction databases in the Ginoux and Walker simulations produced similar dust loading which was more realistic than that produced in the Idealized lofting simulations. Idealized lofting in this case study generated unrealistically large amounts of dust compared with observations of aerosol optical depth (AOD) due to the lack of locational constraints. Generally, the simulations with enhanced dust mass via surface lofting experienced reductions in daytime insolation due to aerosol scattering effects as well as reductions in nighttime radiative cooling due to aerosol absorption effects. These radiative responses were magnified with increasing amounts of dust loading. In the Idealized simulation with extreme (AOD > 5) dust amounts, these radiative responses suppressed the diurnal temperature range. In the Ginoux and Walker simulations with moderate (AOD ∼1–3) amounts of lofted dust, the presence of dust still strongly impacted the radiative fluxes but only marginally modified the low-level temperature. The dust-induced near-surface temperature change was limited due to competing thermal responses to changes in the net radiative fluxes and the dust-layer radiative heating rates. Compared to the Ginoux simulation, the use of increased resolution in dust-erodible fraction inventories in the Walker simulations led to enhanced fine-scale horizontal variability in lofted dust and a modest increase in the mean dust concentration profile and radiative or thermal responses. This study discusses the utility of using high-resolution dust source databases for simulating lofted dust, the need for greater spatial coverage of in situ aerosol observations in dust-prone regions, the impacts of dust on the local radiation budget and surface thermal conditions, and the potential dust radiative impacts on thermally driven mesoscale features.
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Li, Genong, and Michael F. Modest. "Importance of Turbulence-Radiation Interactions in Turbulent Diffusion Jet Flames." Journal of Heat Transfer 125, no. 5 (September 23, 2003): 831–38. http://dx.doi.org/10.1115/1.1597621.
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Traditional modeling of radiative transfer in reacting flows has ignored turbulence-radiation interactions (TRI). Radiative fluxes, flux divergences and radiative properties have been based on mean temperature and concentration fields. However, both experimental and theoretical work have suggested that mean radiative quantities may differ significantly from those predictions based on the mean parameters because of their strongly nonlinear dependence on the temperature and concentration fields. The composition PDF method is able to consider many nonlinear interactions rigorously, and the method is used here to study turbulence-radiation interactions. This paper tries to answer two basic questions: (1) whether turbulence-radiation interactions are important in turbulent flames or not; and (2) if they are important, then what correlations need to be considered in the simulation to capture them. After conducting many flame simulations, it was observed that, on average, TRI effects account for about 1/3 of the total drop in flame peak temperature caused by radiative heat losses. In addition, this study shows that consideration of the temperature self correlation alone is not sufficient to capture TRI, but that the complete absorption coefficient-Planck function correlation must be considered.
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Makké, Laurent, Luc Musson-Genon, Bertrand Carissimo, Pierre Plion, Maya Milliez, and Alexandre Douce. "A New Method for Fast Computation of Three-Dimensional Atmospheric Infrared Radiative Transfer in a Nonscattering Medium, with an Application to Dynamical Simulation of Radiation Fog in a Built Environment." Journal of the Atmospheric Sciences 73, no. 10 (October 1, 2016): 4137–49. http://dx.doi.org/10.1175/jas-d-15-0012.1.
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Abstract The atmospheric radiation field has seen the development of more accurate and faster methods to take into account absorption. Modeling fog formation, where infrared radiation is involved, requires accurate methods to compute cooling rates. Radiative fog appears under clear-sky conditions owing to a significant cooling during the night where absorption and emission are the dominant processes. Thanks to high-performance computing, high-resolution multispectral approaches to solving the radiative transfer equation are often used. Nevertheless, the coupling of three-dimensional radiative transfer with fluid dynamics is very computationally expensive. Radiation increases the computation time by around 50% over the pure computational fluid dynamics simulation. To reduce the time spent in radiation calculations, a new method using analytical absorption functions fitted by Sasamori on Yamamoto’s radiation chart has been developed to compute an equivalent absorption coefficient (spectrally integrated). Only one solution of the radiative transfer equation is needed against Nband × Ngauss for an Nband model with Ngauss quadrature points on each band. A comparison with simulation data has been done and the new parameterization of radiative properties proposed in this article shows the ability to handle variations of gas concentrations and liquid water.
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Matheou, Georgios, and João Teixeira. "Sensitivity to Physical and Numerical Aspects of Large-Eddy Simulation of Stratocumulus." Monthly Weather Review 147, no. 7 (July 1, 2019): 2621–39. http://dx.doi.org/10.1175/mwr-d-18-0294.1.
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Abstract A series of numerical experiments where both physical and numerical model parameters are varied with respect to a reference setup is used to investigate the physics of a stratocumulus cloud and the performance of a large-eddy simulation (LES) model. The simulations show a delicate balance of physical processes with some sensitivities amplified by numerical model features. A strong feedback between cloud liquid, cloud-top radiative cooling, and turbulence leads to slow grid convergence of the turbulent fluxes. For a methodology that diagnoses cloud liquid from conserved variables, small errors in the total water amount result in large liquid water errors, which are amplified by the cloud-top radiative cooling leading to large variations of buoyancy forcing. In contrast, when the liquid–radiation–buoyancy feedback is not present in simulations without radiation, the turbulence structure of the boundary layer remains essentially identical for grid resolutions between 20 and 1.25 m. The present runs suggest that the buoyancy reversal instability significantly enhances the entrainment rate. Even though cloud-top radiative cooling is regarded as a key attribute of stratocumulus, the present simulations suggest that surface fluxes and surface shear significantly contribute to the total turbulent kinetic energy. Turbulence spectra exhibit inertial range scaling away from the confinement effects of the surface and inversion. Fine grid resolution LESs agree with observations, especially with respect to cloud liquid and vertical velocity variance, and exhibit grid convergence without any model tuning or ad hoc model choices.
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Salim, Mohamed H., Sebastian Schubert, Jaroslav Resler, Pavel Krč, Björn Maronga, Farah Kanani-Sühring, Matthias Sühring, and Christoph Schneider. "Importance of radiative transfer processes in urban climate models: a study based on the PALM 6.0 model system." Geoscientific Model Development 15, no. 1 (January 10, 2022): 145–71. http://dx.doi.org/10.5194/gmd-15-145-2022.
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Abstract. Including radiative transfer processes within the urban canopy layer into microscale urban climate models (UCMs) is essential to obtain realistic model results. These processes include the interaction of buildings and vegetation with shortwave and longwave radiation, thermal emission, and radiation reflections. They contribute differently to the radiation budget of urban surfaces. Each process requires different computational resources and physical data for the urban elements. This study investigates how much detail modellers should include to parameterize radiative transfer in microscale building-resolving UCMs. To that end, we introduce a stepwise parameterization method to the Parallelized Large-eddy Simulation Model (PALM) system 6.0 to quantify individually the effects of the main radiative transfer processes on the radiation budget and on the flow field. We quantify numerical simulations of both simple and realistic urban configurations to identify the major and the minor effects of radiative transfer processes on the radiation budget. The study shows that processes such as surface and vegetation interaction with shortwave and longwave radiation will have major effects, while a process such as multiple reflections will have minor effects. The study also shows that radiative transfer processes within the canopy layer implicitly affect the incoming radiation since the radiative transfer model is coupled to the radiation model. The flow field changes considerably in response to the radiative transfer processes included in the model. The study identified those processes which are essentially needed to assure acceptable quality of the flow field. These processes are receiving radiation from atmosphere based on the sky-view factors, interaction of urban vegetation with radiation, radiative transfer among urban surfaces, and considering at least single reflection of radiation. Omitting any of these processes may lead to high uncertainties in the model results.
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Crnomarkovic, Nenad, Miroslav Sijercic, Srdjan Belosevic, Dragan Tucakovic, and Titoslav Zivanovic. "Influence of application of Hottel’s zonal model and six-flux model of thermal radiation on numerical simulations results of pulverized coal fired furnace." Thermal Science 16, no. 1 (2012): 271–82. http://dx.doi.org/10.2298/tsci110627126c.
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Difference of results of numerical simulation of pulverized coal fired furnace when mathematical models contain various radiation models has been described in paper. Two sets of numerical simulations of pulverized coal fired furnace of 210 MWe power boiler have been performed. One numerical simulation has contained Hottel?s zonal model, whereas the other numerical simulation has contained six-flux model. Other details of numerical simulations have been identical. The influence of radiation models has been examined through comparison of selected variables (gas-phase temperature, oxygen concentration, and absorbed radiative heat rate of surface zones of rear and right furnace walls), selected global parameters of furnace operation (total absorbed heat rate by all furnace walls and furnace exit gas-phase temperature). Computation time has been compared as well. Spatially distributed variables have been compared through maximal local differences and mean differences. Maximal local difference of gas-phase temperature has been 8.44%. Maximal local difference of absorbed radiative heat rate of the surface zones has been almost 80.0%. Difference of global parameters of furnace operation has been expressed in percents of value obtained by mathematical model containing Hottel?s zonal model and has not been bigger than 7.0%. Computation time for calculation of 1000 iterations has been approximately the same. Comparison with other radiation models is necessary for assessment of differences.
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Zhang, Tianyu, Jiming Sun, and Yi Yang. "A Numerical Study of Effects of Radiation on Deep Convective Warm Based Cumulus Cloud Development with a 3-D Radiative Transfer Model." Atmosphere 11, no. 11 (November 2, 2020): 1187. http://dx.doi.org/10.3390/atmos11111187.
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The effects of radiation heating and cooling on cumulus cloud development have been the focus of considerable attention for many years. However, it is still not clear how radiation impacts cloud droplet growth. Since cloud inhomogeneity has a great influence on radiation transmission, we coupled the 3D atmospheric radiative transfer model using the spherical harmonic discrete ordinate method with WRF-LES, which can improve the simulation accuracy of the inhomogeneous effect of clouds on radiation compared with that of the 1D radiation method. The shortwave and longwave radiation fluxes for upward and downward directions were simulated with different solar zenith angles. The comparison of 1D and 3D radiative solvers for deep convective cloud cases shows that the 3D radiative solver provides an accurate structure of solar and thermal radiation characteristics and the spatial distribution field. The solar radiation heating is likely to increase perpendicular to the solar incidence direction. For longwave radiation, the cooling effect on the cloud top and the heating effect on the cloud base are both more intense in the 3D radiation model. This study focuses on 3D cloud-radiative interactions in an inhomogeneous cloud field in a large eddy simulation, and the results suggest that compared with the widely used 1D radiative solver in WRF, the 3D radiation model can provide a precise description of the radiation field in an inhomogeneous atmosphere.
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Simon, Helge, Tim Sinsel, and Michael Bruse. "Advances in Simulating Radiative Transfer in Complex Environments." Applied Sciences 11, no. 12 (June 11, 2021): 5449. http://dx.doi.org/10.3390/app11125449.
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Accurate simulation of radiative transfer is a very important aspect in climate modeling. For microclimate models in particular, it is not only important to simulate primary but also secondary radiative fluxes in great detail, i.e., emitted longwave and reflected shortwave radiation. As there are always limitations regarding computational effort and memory, these radiative fluxes are commonly implemented using simplified approaches. To overcome these simplifications and, thus, increase modeling accuracy, a new radiation scheme called indexed view sphere was introduced into the microclimate model ENVI-met. This new scheme actually accounts for radiative contributions of objects that are seen by each grid cell. In order to evaluate the advantages of the new scheme, it is compared against the formerly used averaged view factor scheme. The comparison in a complex realistic urban environment demonstrated that the indexed view sphere scheme improved the accuracy and plausibility of modeling radiative fluxes. It, however, yields an increased demand of memory to store the view facets for each cell. The higher accuracy in simulating secondary radiative fluxes should, however, overturn this shortcoming for most studies, as more detailed knowledge of local microclimatic conditions in general and eventually thermal comfort can be gained.
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Kylling, A., R. Buras, S. Eckhardt, C. Emde, B. Mayer, and A. Stohl. "Simulation of SEVIRI infrared channels: a case study from the Eyjafjallajökull April/May 2010 eruption." Atmospheric Measurement Techniques 6, no. 3 (March 13, 2013): 649–60. http://dx.doi.org/10.5194/amt-6-649-2013.
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Abstract. Infrared satellite images are widely and successfully used to detect and follow atmospheric ash from erupting volcanoes. We describe a new radiative transfer model framework for the simulation of infrared radiances, which can be compared directly with satellite images. This can be helpful to get insight into the processes that affect the satellite retrievals. As input to the radiative transfer model, the distribution of ash is provided by simulations with the FLEXPART Lagrangian particle dispersion model, meteorological cloud information is adopted from the ECMWF analysis and the radiative transfer modelling is performed with the MYSTIC 3-D radiative transfer model. The model framework is used to study an episode during the Eyjafjallajökull eruption in 2010. It is found that to detect ash by the reverse absorption retrieval technique, accurate representation of the ash particle size distribution is required. Detailed investigation of individual pixels displays the radiative effects of various combinations of ash, liquid water and ice clouds. In order to be clearly detectable, the ash clouds need to be located at some distance above other clouds. If ash clouds are mixed with water clouds or are located only slightly above water clouds, detection of the ash becomes difficult. Simulations were also made using the so-called independent pixel approximation (IPA) instead of the fully 3-D radiative transfer modelling. In the two simulations, different clouds (or different parts of the clouds) or the ground are effectively emitting radiation towards the instrument, thus causing differences in the brightness temperature of up to ± 25 K. The presented model framework is useful for further studies of the processes that affect satellite imagery and may be used to test both new and existing ash retrieval algorithms.
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Atashafrooz, M., and SA Gandjalikhan Nassab. "Simulation of three-dimensional laminar forced convection flow of a radiating gas over an inclined backward-facing step in a duct under bleeding condition." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 227, no. 2 (May 17, 2012): 332–45. http://dx.doi.org/10.1177/0954406212447657.
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This study presents a numerical analysis of three-dimensional laminar forced convection flow of a radiating gas over an inclined backward-facing step in a rectangular duct under bleeding condition. The fluid is treated as a gray, absorbing, emitting, and scattering medium. The three-dimensional Cartesian coordinate system is used to solve the governing equations which are the conservations of mass, momentum, and energy. These equations are solved numerically using the computational fluid dynamic techniques to obtain the temperature and velocity fields, while the blocked-off method is employed to simulate the incline surface. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. Since the gas is considered as a radiating medium, besides the convective and conductive terms in the energy equation, the radiative term also presented. For computation of this term, the radiative transfer equation is solved numerically by the discrete ordinates method to find the divergence of radiative heat flux distribution inside the radiating medium. By this numerical procedure, the role of radiation heat transfer on convection flow of a radiating gas which has many engineering applications (for example in heat exchangers and combustion chambers) is studied in detail. Beside, the effects of bleeding coefficient, albedo coefficient, optical thickness, and the radiation–conduction parameter on heat transfer behavior of the system are investigated. Comparison of numerical results with the available data published in the open literature shows a good agreement.
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Wang, Yansen, Xiping Zeng, and Jonathan Decker. "A GPU-Accelerated Radiation Transfer Model Using the Lattice Boltzmann Method." Atmosphere 12, no. 10 (October 9, 2021): 1316. http://dx.doi.org/10.3390/atmos12101316.
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A prototype of a three-dimensional (3-D) radiation model is developed using the lattice Boltzmann method (LBM) and implemented on a graphical processing unit (GPU) to accelerate the model’s computational speed. This radiative transfer-lattice Boltzmann model (RT-LBM) results from a discretization of the radiative transfer equation in time, space, and solid angle. The collision and streaming computation algorithm, widely used in LBM for fluid flow modeling, is applied to speed up the RT-LBM computation on the GPU platform. The isotropic scattering is assumed in this study. The accuracy is evaluated using Monte Carlo method (MCM) simulations, showing RT-LBM is quite accurate when typical atmospheric coefficients of scattering and absorption are used. RT-LBM runs about 10 times faster than the MCM in a same CPU. When implemented on a NVidia Tesla V100 GPU in simulation with a large number of computation grid points, for example, RT-LBM runs ~120 times faster than running on a single CPU. The test results indicate RT-LBM is an accurate and fast model and is viable for simulating radiative transfer in the atmosphere with ranges for the isotropic atmosphere radiative parameters of albedo scattering (0.1~0.9) and optical depth (0.1~12).
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Zhang, Tiejun, Cailing Zhao, Chongshui Gong, and ZhaoXia Pu. "Simulation of Wind Speed Based on Different Driving Datasets and Parameterization Schemes Near Dunhuang Wind Farms in Northwest of China." Atmosphere 11, no. 6 (June 18, 2020): 647. http://dx.doi.org/10.3390/atmos11060647.
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In this study, we evaluate the impacts of different datasets (e.g., NCEP global forecast system (GFS) and ERA5) that are used to derive the initial and boundary conditions, various planetary parameterization boundary layer (PBL) schemes and radiation parameterization schemes on wind speed simulations over wind farms near Dunhuang in Northwest of China. The mesoscale community Weather Research and Forecasting (WRF) model is employed to simulate the wind speeds in March of 2014. The sensitivity of numerical simulations to different PBL schemes, including the Yonsei University (YSU), the Asymmetric Convective Model (ACM2) and the Mellor–Yamada–Janjic (MYJ) scheme are examined. Besides, simulations with different radiation parameterization schemes, including the Rapid Radiative Transfer Model for general circulation model (GCM) applications (RRTMG) and the Fu–Liou–Gu radiative transfer scheme (FLG), are compared. Based on hourly observation data from three national basic meteorological observing stations and an anemometer tower in Dunhuang, the simulation results are evaluated. Results show that, using the GFS data as the initial data, the simulation error of 10-m wind speed is rather smaller under the combination of the YSU and FLG. When using the ERA5 data as the initial data, the error of the 2-m temperature simulation is smaller, and it is also less than that of the 10-m wind speed simulation. The simulation results show significant differences at different altitudes. The relative error of wind speed is larger at higher altitude. In the vertical direction, the wind speed is smaller at a lower height and so is the simulation error. In terms of wind speed from the anemometer tower, the error of the wind speed is related to the magnitude of the observed wind speed. Therefore, according to specific conditions of the simulated area, selecting an appropriate combination of initial data and parameterization schemes can effectively reduce the errors of simulated wind speed.
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Zube, Nicholas G., Xi Zhang, Tao Li, Tianhao Le, Cheng Li, Sandrine Guerlet, and Xianyu Tan. "Radiative-dynamical Simulation of Jupiter’s Stratosphere and Upper Troposphere." Astrophysical Journal 921, no. 2 (November 1, 2021): 174. http://dx.doi.org/10.3847/1538-4357/ac1e95.
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Abstract We present a two-dimensional radiative-dynamical model of the combined stratosphere and upper troposphere of Jupiter to understand its temperature distribution and meridional circulation pattern. Our study highlights the importance of radiative and mechanical forcing for driving the middle atmospheric circulation on Jupiter. Our model adopts a state-of-the-art radiative transfer scheme with recent observations of Jovian gas abundances and haze distribution. Assuming local radiative equilibrium, latitudinal variation of hydrocarbon abundances is not able to explain the observed latitudinal temperature variations in the mid-latitudes. With mechanical forcing parameterized as a frictional drag on zonal wind, our model produces ∼2 K latitudinal temperature variations observed in low to mid-latitudes in the troposphere and lower stratosphere, but cannot reproduce the observed 5 K temperature variations in the middle stratosphere. In the high latitudes, temperature and meridional circulation depend strongly on polar haze radiation. The simulated residual mean circulation shows either two broad equator-to-pole cells or multi-cell patterns, depending on the frictional drag timescale and polar haze properties. A more realistic wave parameterization and a better observational characterization of haze distribution and optical properties are needed to better understand latitudinal temperature distributions and circulation patterns in the middle atmosphere of Jupiter.
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Verlinden, Kathryn L., and Simon P. de Szoeke. "Simulating Radiative Fluxes through Southeastern Pacific Stratocumulus Clouds during VOCALS-REx." Journal of Atmospheric and Oceanic Technology 35, no. 4 (April 2018): 821–36. http://dx.doi.org/10.1175/jtech-d-17-0169.1.
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ABSTRACTTime series of solar and thermal infrared radiative flux profiles are simulated with the Rapid Radiative Transfer Model (RRTM) using a hierarchy of constraints from radar reflectivity and passive microwave cloud remote sensing measurements collected over a ship in the southeastern tropical Pacific Ocean (20°S) during the second leg of the Variability of American Monsoon Systems (VAMOS) Ocean–Cloud–Atmosphere–Land Study Regional Experiment (VOCALS-REx). Incorporating additional constraints results in simulations of physically consistent radiative profiles throughout the atmosphere, especially within the cloud, where they are difficult to observe precisely. Simulated surface radiative fluxes are compared with those observed on the ship and by aircraft.Due to the strong Rayleigh scattering of drizzle drops compared to cloud droplets that absorb, emit, and scatter natural radiation, cloud radar reflectivity overestimates cloud liquid water content (LWC). As a result, clouds are optically too thick and transmission ratios are too low in simulations using radar LWC. Imposing a triangular (increasing linearly with height from zero at cloud base) LWC profile in agreement with microwave liquid water path (LWP) improves the simulation of the transmission ratio. Constraining the corresponding microphysical cloud effective radius to that retrieved from optical depth, LWP, and cloud thickness results in additional improvements to the simulations. Time series, averages, and composite diurnal cycles of radiative fluxes, heating rates, and cloud radiative forcing are presented.
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Emde, C., and B. Mayer. "Simulation of solar radiation during a total eclipse: a challenge for radiative transfer." Atmospheric Chemistry and Physics 7, no. 9 (May 4, 2007): 2259–70. http://dx.doi.org/10.5194/acp-7-2259-2007.
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Abstract. A solar eclipse is a rare but spectacular natural phenomenon and furthermore it is a challenge for radiative transfer modelling. Whereas a simple one-dimensional radiative transfer model with reduced solar irradiance at the top of the atmosphere can be used to calculate the brightness during partial eclipses a much more sophisticated model is required to calculate the brightness (i.e. the diffuse radiation) during the total eclipse. The reason is that radiation reaching a detector in the shadow gets there exclusively by horizontal transport of photons in a spherical shell atmosphere, which requires a three-dimensional radiative transfer model. In this study the first fully three-dimensional simulations for a solar eclipse are presented exemplified by the solar eclipse at 29 March 2006. Using a backward Monte Carlo model we calculated the diffuse radiation in the umbra and simulated the changing colours of the sky. Radiance and irradiance are decreased by 3 to 4 orders of magnitude, depending on wavelength. We found that aerosol has a comparatively small impact on the radiation in the umbra. We also estimated the contribution of the solar corona to the radiation under the umbra and found that it is negligible compared to the diffuse solar radiation in the wavelength region from 310 to 500 nm.
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Mignon-Risse, R., M. González, B. Commerçon, and J. Rosdahl. "A new hybrid radiative transfer method for massive star formation." Astronomy & Astrophysics 635 (March 2020): A42. http://dx.doi.org/10.1051/0004-6361/201936605.
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Context. Frequency-dependent and hybrid approaches for the treatment of stellar irradiation are of primary importance in numerical simulations of massive star formation. Aims. We seek to compare outflow and accretion mechanisms in star formation simulations. We investigate the accuracy of a hybrid radiative transfer method using the gray M1 closure relation for proto-stellar irradiation and gray flux-limited diffusion (FLD) for photons emitted everywhere else. Methods. We have coupled the FLD module of the adaptive-mesh refinement code RAMSES with RAMSES-RT, which is based on the M1 closure relation and the reduced speed-of-light-approximation. Our hybrid (M1+FLD) method takes an average opacity at the stellar temperature for the M1 module, instead of the local environmental radiation field. Due to their construction, the opacities are consistent with the photon origin. We have tested this approach in radiative transfer tests of disks irradiated by a star for three levels of optical thickness and compared the temperature structure with the radiative transfer codes RADMC-3D and MCFOST. We applied it to a radiation-hydrodynamical simulation of massive star formation. Results. Our tests validate our hybrid approach for determining the temperature structure of an irradiated disk in the optically-thin (2% maximal error) and moderately optically-thick (error smaller than 25%) regimes. The most optically-thick test shows the limitation of our hybrid approach with a maximal error of 65% in the disk mid-plane against 94% with the FLD method. The optically-thick setups highlight the ability of the hybrid method to partially capture the self-shielding in the disk while the FLD alone cannot. The radiative acceleration is ≈100 times greater with the hybrid method than with the FLD. The hybrid method consistently leads to about + 50% more extended and wider-angle radiative outflows in the massive star formation simulation. We obtain a 17.6 M⊙ star at t ≃ 0.7τff, while the accretion phase is still ongoing, with a mean accretion rate of ≃7 × 10−4 M⊙ yr−1. Finally, despite the use of refinement to resolve the radiative cavities, no Rayleigh–Taylor instability appears in our simulations, and we justify their absence by physical arguments based on the entropy gradient.
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Rempel, M., M. Schüssler, and M. Knölker. "RADIATIVE MAGNETOHYDRODYNAMIC SIMULATION OF SUNSPOT STRUCTURE." Astrophysical Journal 691, no. 1 (January 16, 2009): 640–49. http://dx.doi.org/10.1088/0004-637x/691/1/640.
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Gristey, Jake J., Graham Feingold, Ian B. Glenn, K. Sebastian Schmidt, and Hong Chen. "Surface Solar Irradiance in Continental Shallow Cumulus Fields: Observations and Large-Eddy Simulation." Journal of the Atmospheric Sciences 77, no. 3 (March 1, 2019): 1065–80. http://dx.doi.org/10.1175/jas-d-19-0261.1.
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Abstract This study examines shallow cumulus cloud fields and their surface shortwave radiative effects using large-eddy simulation (LES) along with observations across multiple days at the Atmospheric Radiation Measurement Southern Great Plains atmospheric observatory. Pronounced differences are found between probability density functions (PDFs) of downwelling surface solar irradiance derived from observations and LES one-dimensional (1D) online radiation calculations. The shape of the observed PDF is bimodal, which is only reproduced by offline three-dimensional (3D) radiative transfer calculations, demonstrating PDF bimodality as a 3D radiative signature of continental shallow cumuli. Local differences between 3D and 1D radiative transfer calculations of downwelling surface solar irradiance are, on average, larger than 150 W m−2 on one afternoon. The differences are substantially reduced when spatially averaged over the LES domain and temporally averaged over the diurnal cycle, but systematic 3D biases ranging from 2 to 8 W m−2 persist across different days. Covariations between the domain-averaged surface irradiance, framed as a surface cloud radiative effect, and the simulated cloud fraction are found to follow a consistent diurnal relationship, often exhibiting hysteresis. In contrast, observations show highly variable behavior. By subsampling the LES domain, it is shown that this is due to the limited sampling density of inherently 3D observations. These findings help to define observational requirements for detecting such relationships, provide valuable insight for evaluating weather and climate models against surface observations as they push to ever higher resolutions, and have important implications for future assessments of solar renewable energy potential.
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Heidari, Mohammad Reza, Zhaoyang Song, Enrico Degregori, Jörg Behrens, and Hendryk Bockelmann. "Concurrent calculation of radiative transfer in the atmospheric simulation in ECHAM-6.3.05p2." Geoscientific Model Development 14, no. 12 (December 6, 2021): 7439–57. http://dx.doi.org/10.5194/gmd-14-7439-2021.
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Abstract. The scalability of the atmospheric model ECHAM6 at low resolution, as used in palaeoclimate simulations, suffers from the limited number of grid points. As a consequence, the potential of current high-performance computing architectures cannot be used at full scale for such experiments, particularly within the available domain decomposition approach. Radiation calculations are a relatively expensive part of the atmospheric simulations, taking up to approximately 50 % or more of the total runtime. This current level of cost is achieved by calculating the radiative transfer only once in every 2 h of simulation. In response, we propose extending the available concurrency within the model further by running the radiation component in parallel with other atmospheric processes to improve scalability and performance. This paper introduces the concurrent radiation scheme in ECHAM6 and presents a thorough analysis of its impact on the performance of the model. It also evaluates the scientific results from such simulations. Our experiments show that ECHAM6 can achieve a speedup of over 1.9× using the concurrent radiation scheme. By performing a suite of stand-alone atmospheric experiments, we evaluate the influence of the concurrent radiation scheme on the scientific results. The simulated mean climate and internal climate variability by the concurrent radiation generally agree well with the classical radiation scheme, with minor improvements in the mean atmospheric circulation in the Southern Hemisphere and the atmospheric teleconnection to the Southern Annular Mode. This empirical study serves as a successful example that can stimulate research on other concurrent components in atmospheric modelling whenever scalability becomes challenging.
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Chapman, E. G., W. I. Gustafson, R. C. Easter, J. C. Barnard, S. J. Ghan, M. S. Pekour, and J. D. Fast. "Coupling aerosol-cloud-radiative processes in the WRF-Chem model: Investigating the radiative impact of elevated point sources." Atmospheric Chemistry and Physics 9, no. 3 (February 6, 2009): 945–64. http://dx.doi.org/10.5194/acp-9-945-2009.
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Abstract. The local and regional influence of elevated point sources on summertime aerosol forcing and cloud-aerosol interactions in northeastern North America was investigated using the WRF-Chem community model. The direct effects of aerosols on incoming solar radiation were simulated using existing modules to relate aerosol sizes and chemical composition to aerosol optical properties. Indirect effects were simulated by adding a prognostic treatment of cloud droplet number and adding modules that activate aerosol particles to form cloud droplets, simulate aqueous-phase chemistry, and tie a two-moment treatment of cloud water (cloud water mass and cloud droplet number) to precipitation and an existing radiation scheme. Fully interactive feedbacks thus were created within the modified model, with aerosols affecting cloud droplet number and cloud radiative properties, and clouds altering aerosol size and composition via aqueous processes, wet scavenging, and gas-phase-related photolytic processes. Comparisons of a baseline simulation with observations show that the model captured the general temporal cycle of aerosol optical depths (AODs) and produced clouds of comparable thickness to observations at approximately the proper times and places. The model overpredicted SO2 mixing ratios and PM2.5 mass, but reproduced the range of observed SO2 to sulfate aerosol ratios, suggesting that atmospheric oxidation processes leading to aerosol sulfate formation are captured in the model. The baseline simulation was compared to a sensitivity simulation in which all emissions at model levels above the surface layer were set to zero, thus removing stack emissions. Instantaneous, site-specific differences for aerosol and cloud related properties between the two simulations could be quite large, as removing above-surface emission sources influenced when and where clouds formed within the modeling domain. When summed spatially over the finest resolution model domain (the extent of which corresponds to the typical size of a single global climate model grid cell) and temporally over a three day analysis period, total rainfall in the sensitivity simulation increased by 31% over that in the baseline simulation. Fewer optically thin clouds, arbitrarily defined as a cloud exhibiting an optical depth less than 1, formed in the sensitivity simulation. Domain-averaged AODs dropped from 0.46 in the baseline simulation to 0.38 in the sensitivity simulation. The overall net effect of additional aerosols attributable to primary particulates and aerosol precursors from point source emissions above the surface was a domain-averaged reduction of 5 W m−2 in mean daytime downwelling shortwave radiation.
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Chapman, E. G., W. I. Gustafson,, R. C. Easter, J. C. Barnard, S. J. Ghan, M. S. Pekour, and J. D. Fast. "Coupling aerosol-cloud-radiative processes in the WRF-Chem model: investigating the radiative impact of elevated point sources." Atmospheric Chemistry and Physics Discussions 8, no. 4 (August 1, 2008): 14765–817. http://dx.doi.org/10.5194/acpd-8-14765-2008.
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Abstract. The local and regional influence of elevated point sources on summertime aerosol forcing and cloud-aerosol interactions in northeastern North America was investigated using the WRF-Chem community model. The direct effects of aerosols on incoming solar radiation were simulated using existing modules to relate aerosol sizes and chemical composition to aerosol optical properties. Indirect effects were simulated by adding a prognostic treatment of cloud droplet number and adding modules that activate aerosol particles to form cloud droplets, simulate aqueous-phase chemistry, and tie a two-moment treatment of cloud water (cloud water mass and cloud droplet number) to an existing radiation scheme. Fully interactive feedbacks thus were created within the modified model, with aerosols affecting cloud droplet number and cloud radiative properties, and clouds altering aerosol size and composition via aqueous processes, wet scavenging, and gas-phase-related photolytic processes. Comparisons of a baseline simulation with observations show that the model captured the general temporal cycle of aerosol optical depths (AODs) and produced clouds of comparable thickness to observations at approximately the proper times and places. The model overpredicted SO2 mixing ratios and PM2.5 mass, but reproduced the range of observed SO2 to sulfate aerosol ratios, suggesting that atmospheric oxidation processes leading to aerosol sulfate formation are captured in the model. The baseline simulation was compared to a sensitivity simulation in which all emissions at model levels above the surface layer were set to zero, thus removing stack emissions. Instantaneous, site-specific differences for aerosol and cloud related properties between the two simulations could be quite large, as removing above-surface emission sources influenced when and where clouds formed within the modeling domain. When summed spatially over the finest resolution model domain (the extent of which corresponds to the typical size of a single GCM grid cell) and temporally over a three day analysis period, total rainfall in the sensitivity simulation increased by 31% over that in the baseline simulation. Fewer optically thin clouds, arbitrarily defined as a cloud exhibiting an optical depth less than 1, formed in the sensitivity simulation. Domain-averaged AODs dropped from 0.46 in the baseline simulation to 0.38 in the sensitivity simulation. The overall net effect of additional aerosols attributable to primary particulates and aerosol precursors from point source emissions above the surface was a domain-averaged reduction of 5 W m−2 in mean daytime downwelling shortwave radiation.
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Santese, M., M. R. Perrone, A. S. Zakey, F. De Tomasi, and F. Giorgi. "Modeling of Saharan dust outbreaks over the Mediterranean by RegCM3: case studies." Atmospheric Chemistry and Physics Discussions 9, no. 5 (September 17, 2009): 19387–433. http://dx.doi.org/10.5194/acpd-9-19387-2009.
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Abstract. The regional climate model RegCM3 coupled with a radiatively active aerosol model with online feedback is used to investigate direct and semi-direct radiative aerosol effects over the Sahara and Europe in a test case of July 2003. The aerosol model includes dust particles in addition to sulfates, hydrophobic and hydrophilic black carbon and organic carbon. The role of the aerosol online feedback on the radiation budget and the direct radiative forcing (short-wave and long-wave) by dust particles are investigated by intercomparing results from three experiments: REF, including all interactive aerosol components, Exp1, not accounting for the aerosol radiative feedback, and Exp2 not accounting for desert dust particles. The comparison of results in the REF experiment with satellite observations, sun/sky radiometer measurements, and lidar profiles at selected Central Mediterranean sites reveals that the spatio-temporal evolution of the aerosol optical depth is reasonably well reproduced by the model during the entire month of July. Results for the dust outbreaks of 17 and 24 July, averaged over the simulation domain, show that the daily-mean SW direct radiative forcing by all particles is −24 W/m2 and −3.4 W/m2 on 17 July and −25 W/m2 and −3.5 W/m2 on 24 July at the surface and top of the atmosphere, respectively. This is partially offset by a LW direct radiative forcing of ~30% at the surface and of ~50% at the ToA. It is also shown that atmospheric dynamics and hence dust production and advection processes are dependent on the simulation assumptions and may significantly change within few tens of kilometers. The comparison of REF and Exp1 shows that the aerosol online feedback on the radiation budget decreases the domain-average daily-mean value of the 2 m-temperature, aerosol column burden (CB), and short-wave (SW) atmospheric forcing by 0.52°C, 14%, and 0.9%, respectively on 17 July and by 0.39°C, 12% and 12%, respectively on 24 July. The comparison of REF and Exp2 reveals that on 17 July, radiatively-active dust particles decrease the daily-mean 2-m temperature averaged over the whole simulation domain by 0.12°C even if are responsible for 99.8% and 97% of the daily-mean aerosol column burden and SW atmospheric forcing, respectively.
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Xia, Yan, Yongyun Hu, and Yi Huang. "Strong modification of stratospheric ozone forcing by cloud and sea-ice adjustments." Atmospheric Chemistry and Physics 16, no. 12 (June 21, 2016): 7559–67. http://dx.doi.org/10.5194/acp-16-7559-2016.
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Abstract. We investigate the climatic impact of stratospheric ozone recovery (SOR), with a focus on the surface temperature change in atmosphere–slab ocean coupled climate simulations. We find that although SOR would cause significant surface warming (global mean: 0.2 K) in a climate free of clouds and sea ice, it causes surface cooling (−0.06 K) in the real climate. The results here are especially interesting in that the stratosphere-adjusted radiative forcing is positive in both cases. Radiation diagnosis shows that the surface cooling is mainly due to a strong radiative effect resulting from significant reduction of global high clouds and, to a lesser extent, from an increase in high-latitude sea ice. Our simulation experiments suggest that clouds and sea ice are sensitive to stratospheric ozone perturbation, which constitutes a significant radiative adjustment that influences the sign and magnitude of the global surface temperature change.
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Yoshioka, Masaru, Natalie M. Mahowald, Andrew J. Conley, William D. Collins, David W. Fillmore, Charles S. Zender, and Dani B. Coleman. "Impact of Desert Dust Radiative Forcing on Sahel Precipitation: Relative Importance of Dust Compared to Sea Surface Temperature Variations, Vegetation Changes, and Greenhouse Gas Warming." Journal of Climate 20, no. 8 (April 15, 2007): 1445–67. http://dx.doi.org/10.1175/jcli4056.1.
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Abstract The role of direct radiative forcing of desert dust aerosol in the change from wet to dry climate observed in the African Sahel region in the last half of the twentieth century is investigated using simulations with an atmospheric general circulation model. The model simulations are conducted either forced by the observed sea surface temperature (SST) or coupled with the interactive SST using the Slab Ocean Model (SOM). The simulation model uses dust that is less absorbing in the solar wavelengths and has larger particle sizes than other simulation studies. As a result, simulations show less shortwave absorption within the atmosphere and larger longwave radiative forcing by dust. Simulations using SOM show reduced precipitation over the intertropical convergence zone (ITCZ) including the Sahel region and increased precipitation south of the ITCZ when dust radiative forcing is included. In SST-forced simulations, on the other hand, significant precipitation changes are restricted to over North Africa. These changes are considered to be due to the cooling of global tropical oceans as well as the cooling of the troposphere over North Africa in response to dust radiative forcing. The model simulation of dust cannot capture the magnitude of the observed increase of desert dust when allowing dust to respond to changes in simulated climate, even including changes in vegetation, similar to previous studies. If the model is forced to capture observed changes in desert dust, the direct radiative forcing by the increase of North African dust can explain up to 30% of the observed precipitation reduction in the Sahel between wet and dry periods. A large part of this effect comes through atmospheric forcing of dust, and dust forcing on the Atlantic Ocean SST appears to have a smaller impact. The changes in the North and South Atlantic SSTs may account for up to 50% of the Sahel precipitation reduction. Vegetation loss in the Sahel region may explain about 10% of the observed drying, but this effect is statistically insignificant because of the small number of years in the simulation. Greenhouse gas warming seems to have an impact to increase Sahel precipitation that is opposite to the observed change. Although the estimated values of impacts are likely to be model dependent, analyses suggest the importance of direct radiative forcing of dust and feedbacks in modulating Sahel precipitation.
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Melot, Matthieu, Jean-Yves Trépanier, Ricardo Camarero, and Eddy Petro. "Comparison of Two Models for Radiative Heat Transfer in High Temperature Thermal Plasmas." Modelling and Simulation in Engineering 2011 (2011): 1–7. http://dx.doi.org/10.1155/2011/285108.
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Numerical simulation of the arc-flow interaction in high-voltage circuit breakers requires a radiation model capable of handling high-temperature participating thermal plasmas. The modeling of the radiative transfer plays a critical role in the overall accuracy of such CFD simulations. As a result of the increase of computational power, CPU intensive methods based on the radiative transfer equation, leading to more accurate results, are now becoming attractive alternatives to current approximate models. In this paper, the predictive capabilities of the finite volume method (RTE-FVM) and the P1 model are investigated. A systematic comparison between these two models and analytical solutions are presented for a variety of relevant test cases. Two implementations of each approach are compared, and a critical evaluation is presented.
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Klinger, Carolin, Graham Feingold, and Takanobu Yamaguchi. "Cloud droplet growth in shallow cumulus clouds considering 1-D and 3-D thermal radiative effects." Atmospheric Chemistry and Physics 19, no. 9 (May 14, 2019): 6295–313. http://dx.doi.org/10.5194/acp-19-6295-2019.
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Abstract. The effect of 1-D and 3-D thermal radiation on cloud droplet growth in shallow cumulus clouds is investigated using large eddy simulations with size-resolved cloud microphysics. A two-step approach is used for separating microphysical effects from dynamical feedbacks. In step one, an offline parcel model is used to describe the onset of rain. The growth of cloud droplets to raindrops is simulated with bin-resolved microphysics along previously recorded Lagrangian trajectories. It is shown that thermal heating and cooling rates can enhance droplet growth and raindrop production. Droplets grow to larger size bins in the 10–30 µm radius range. The main effect in terms of raindrop production arises from recirculating parcels, where a small number of droplets are exposed to strong thermal cooling at cloud edge. These recirculating parcels, comprising about 6 %–7 % of all parcels investigated, make up 45 % of the rain for the no-radiation simulation and up to 60 % when 3-D radiative effects are considered. The effect of 3-D thermal radiation on rain production is stronger than that of 1-D thermal radiation. Three-dimensional thermal radiation can enhance the rain amount up to 40 % compared to standard droplet growth without radiative effects in this idealized framework. In the second stage, fully coupled large eddy simulations show that dynamical effects are stronger than microphysical effects, as far as the production of rain is concerned. Three-dimensional thermal radiative effects again exceed one-dimensional thermal radiative effects. Small amounts of rain are produced in more clouds (over a larger area of the domain) when thermal radiation is applied to microphysics. The dynamical feedback is shown to be an enhanced cloud circulation with stronger subsiding shells at the cloud edges due to thermal cooling and stronger updraft velocities in the cloud center. It is shown that an evaporation–circulation feedback reduces the amount of rain produced in simulations where 3-D thermal radiation is applied to microphysics and dynamics, in comparison to where 3-D thermal radiation is only applied to dynamics.
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Wu, Xiaoqing, and Xin-Zhong Liang. "Radiative Effects of Cloud Horizontal Inhomogeneity and Vertical Overlap Identified from a Monthlong Cloud-Resolving Model Simulation." Journal of the Atmospheric Sciences 62, no. 11 (November 1, 2005): 4105–12. http://dx.doi.org/10.1175/jas3565.1.
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Abstract The representation of subgrid horizontal and vertical variability of clouds in radiation schemes remains a major challenge for general circulation models (GCMs) due to the lack of cloud-scale observations and incomplete physical understanding. The development of cloud-resolving models (CRMs) in the last decade provides a unique opportunity to make progress in this area of research. This paper extends the study of Wu and Moncrieff to quantify separately the impacts of cloud horizontal inhomogeneity (optical property) and vertical overlap (geometry) on the domain-averaged shortwave and longwave radiative fluxes at the top of the atmosphere and the surface, and the radiative heating profiles. The diagnostic radiation calculations using the monthlong CRM-simulated tropical cloud optical properties and cloud fraction show that both horizontal inhomogeneity and vertical overlap of clouds are equally important for obtaining accurate radiative fluxes and heating rates. This study illustrates an objective approach to use long-term CRM simulations to separate cloud overlap and inhomogeneity effects, based on which GCM representation (such as mosaic treatment) of subgrid cloud–radiation interactions can be evaluated and improved.
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EFREMOV, G. F., V. V. SHARKOV, and D. V. KRUPENNIKOV. "NONDIVERGENT STATISTICAL QUANTUM ELECTRODYNAMICS." International Journal of Bifurcation and Chaos 18, no. 09 (September 2008): 2817–24. http://dx.doi.org/10.1142/s0218127408022056.
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Quantum space-time nonlocality, i.e. retardation of the interaction between an electron and its own radiation field at distances about the Compton wavelength, is established. By taking into account a finite variance of electron-coordinate increment in the intrinsic coordinate system, the radiative damping coefficient is obtained as a divergence-free function of frequency that is not subject to the well-known paradoxes of the classical theory of radiative damping. A relation between radiative damping and the electromagnetic mass of the electron is found.
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Park, Sang Seo, Yun Gon Lee, Migyoung Kim, Jaemin Kim, Ja-Ho Koo, Chang Ki Kim, Junshik Um, and Jongmin Yoon. "Simulation of Threshold UV Exposure Time for Vitamin D Synthesis in South Korea." Advances in Meteorology 2019 (January 27, 2019): 1–15. http://dx.doi.org/10.1155/2019/4328151.
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The threshold exposure time for synthesis of vitamin D was simulated by using a radiative transfer model considering variations in total ozone, cloud, and surface conditions. The prediction of total ozone took the form of an empirical linear regression with the variables of meteorological parameters in the upper troposphere and lower stratosphere and the climatology value of total ozone. Additionally, to consider cloud extinction after the estimation of clear-sky UV radiation using a radiative transfer model simulation, a cloud modification factor was applied. The UV irradiance was estimated at one-hour intervals, and then, to improve the temporal resolution of the exposure time simulation, it was interpolated to a one-minute resolution. Exposure times from the simulation clearly followed seasonal and diurnal cycles. However, upon comparison with observations, biases with large variations were found, and the discrepancy in the exposure time between the observations and simulations was higher in low UV irradiance conditions. The large deviations in the prediction errors for total ozone and the simplified assumption for the cloud modification factor contributed to the large deviations in exposure time differences between the model estimation and observations. To improve the accuracy of the simulated exposure time, improved predictions of total ozone with a more detailed cloud treatment will be essential.
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Chao, Yipeng, Xin Luo, Chao Zheng, and Yipeng Chao. "Numerical calculation of passenger compartment cooling effect under the action of radiative cooling film based on MATLAB." Journal of Physics: Conference Series 2125, no. 1 (November 1, 2021): 012027. http://dx.doi.org/10.1088/1742-6596/2125/1/012027.
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Abstract Radiative cooling uses space cold source to cool the object, and the radiative cooling film made by using this principle can be applied to automobiles effectively to save the refrigeration resources of automobiles. However, due to the limitation of economy, time, space and other factors, it is difficult to carry out comprehensive research on the actual film-forming cooling effect. Based on the principle of passive radiative cooling, a set of simulation models is developed, which is applied to the selection of infrared radiation materials for automotive radiative cooling film and the study of the influence of environmental factors on the radiative cooling effect. SiO2 was finally selected as infrared radiation material. At the same time, the theoretical cooling temperature of the radiative cooling film applied to the passenger compartment of automobiles can reach 6.8°C under the conditions of 35°C ambient temperature, 0.99 atmospheric transmittance and 10 heat transfer coefficient, using SiO2 as infrared radiation material and PE as dispersion substrate. At the same time, the cooling effect of the radiative cooling film is positively correlated with the ambient temperature, atmospheric transmittance to some extent.
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Keeler, Jason M., Brian F. Jewett, Robert M. Rauber, Greg M. McFarquhar, Roy M. Rasmussen, Lulin Xue, Changhai Liu, and Gregory Thompson. "Dynamics of Cloud-Top Generating Cells in Winter Cyclones. Part I: Idealized Simulations in the Context of Field Observations." Journal of the Atmospheric Sciences 73, no. 4 (February 24, 2016): 1507–27. http://dx.doi.org/10.1175/jas-d-15-0126.1.
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Abstract This paper assesses the influence of radiative forcing and latent heating on the development and maintenance of cloud-top generating cells (GCs) in high-resolution idealized Weather Research and Forecasting Model simulations with initial conditions representative of the vertical structure of a cyclone observed during the Profiling of Winter Storms campaign. Simulated GC kinematics, structure, and ice mass are shown to compare well quantitatively with Wyoming Cloud Radar, cloud probe, and other observations. Sensitivity to radiative forcing was assessed in simulations with longwave-only (nighttime), longwave-and-shortwave (daytime), and no-radiation parameterizations. The domain-averaged longwave cooling rate exceeded 0.50 K h−1 near cloud top, with maxima greater than 2.00 K h−1 atop GCs. Shortwave warming was weaker by comparison, with domain-averaged values of 0.10–0.20 K h−1 and maxima of 0.50 K h−1 atop GCs. The stabilizing influence of cloud-top shortwave warming was evident in the daytime simulation’s vertical velocity spectrum, with 1% of the updrafts in the 6.0–8.0-km layer exceeding 1.20 m s−1, compared to 1.80 m s−1 for the nighttime simulation. GCs regenerate in simulations with radiative forcing after the initial instability is released but do not persist when radiation is not parameterized, demonstrating that radiative forcing is critical to GC maintenance under the thermodynamic and vertical wind shear conditions in this cyclone. GCs are characterized by high ice supersaturation (RHice > 150%) and latent heating rates frequently in excess of 2.00 K h−1 collocated with vertical velocity maxima. Ice precipitation mixing ratio maxima of greater than 0.15 g kg−1 were common within GCs in the daytime and nighttime simulations.
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Wang, Yuzhu, Yuan Zhao, Wei Li, Jinrong Jiang, Xiaohui Ji, and Albert Y. Zomaya. "Using a GPU to Accelerate a Longwave Radiative Transfer Model with Efficient CUDA-Based Methods." Applied Sciences 9, no. 19 (September 27, 2019): 4039. http://dx.doi.org/10.3390/app9194039.
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Climatic simulations rely heavily on high-performance computing. As one of the atmospheric radiative transfer models, the rapid radiative transfer model for general circulation models (RRTMG) is used to calculate the radiative transfer of electromagnetic radiation through a planetary atmosphere. Radiation physics is one of the most time-consuming physical processes, so the RRTMG presents large-scale and long-term simulation challenges to the development of efficient parallel algorithms that fit well into multicore clusters. This paper presents a method for improving the calculative efficiency of radiation physics, an RRTMG long-wave radiation scheme (RRTMG_LW) that is accelerated on a graphics processing unit (GPU). First, a GPU-based acceleration algorithm with one-dimensional domain decomposition is proposed. Then, a second acceleration algorithm with two-dimensional domain decomposition is presented. After the two algorithms were implemented in Compute Unified Device Architecture (CUDA) Fortran, a GPU version of the RRTMG_LW, namely G-RRTMG_LW, was developed. Results demonstrated that the proposed acceleration algorithms were effective and that the G-RRTMG_LW achieved a significant speedup. In the case without I/O transfer, the 2-D G-RRTMG_LW on one K40 GPU obtained a speed increase of 18.52× over the baseline performance on a single Intel Xeon E5-2680 CPU core.
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GHOSH, S., R. FRIEDRICH, M. PFITZNER, CHR STEMMER, B. CUENOT, and M. EL HAFI. "Effects of radiative heat transfer on the structure of turbulent supersonic channel flow." Journal of Fluid Mechanics 677 (April 15, 2011): 417–44. http://dx.doi.org/10.1017/jfm.2011.92.
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The interaction between turbulence in a minimal supersonic channel and radiative heat transfer is studied using large-eddy simulation. The working fluid is pure water vapour with temperature-dependent specific heats and molecular transport coefficients. Its line spectra properties are represented with a statistical narrow-band correlated-k model. A grey gas model is also tested. The parallel no-slip channel walls are treated as black surfaces concerning thermal radiation and are kept at a constant temperature of 1000 K. Simulations have been performed for different optical thicknesses (based on the Planck mean absorption coefficient) and different Mach numbers. Results for the mean flow variables, Reynolds stresses and certain terms of their transport equations indicate that thermal radiation effects counteract compressibility (Mach number) effects. An analysis of the total energy balance reveals the importance of radiative heat transfer, compared to the turbulent and mean molecular heat transport.
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Moscibrodzka, Monika A., Daniel Proga, Bożena Czerny, and Aneta Siemiginowska. "Radiation spectra from MHD simulations of low angular momentum flows." Proceedings of the International Astronomical Union 2, S238 (August 2006): 411–12. http://dx.doi.org/10.1017/s1743921307005704.
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AbstractWe perform Monte Carlo calculation to determine the radiation spectra from magnetized, low angular momentum accretion flow. Magneto-hydrodynamical simulation (with angular momentum parameter lambda of about 2 Rg c) was performed by Proga & Begelman 2003. Because simulation neglect radiative cooling, we compute electron temperature separately, including ohmic heating, parametrized with small δ coefficient, ion-electron coupling, radiative cooling and advection. Radiation spectra are obtained taking into account, thermal synchrotron and bremsstrahlung radiation, self absorption and Comptonization processes.We show which parts of the flow are responsible for characteristic spectral features and how the spectrum changes in different accretion states. We compare our results with Galactic Center black hole radiation spectra, where low angular momentum accretion is suggested. Accretion state changes seems to be a promising model for the flaring behavior of Galactic Center black hole. We also show the radiation intensity maps in radio and X-rays energy band for viewing angle i = 90°.
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Gatti, C. "Monte Carlo simulation for radiative kaon decays." European Physical Journal C 45, no. 2 (November 30, 2005): 417–20. http://dx.doi.org/10.1140/epjc/s2005-02435-2.
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Nunes Pereira, E. J., M. N. Berberan‐Santos, and J. M. G. Martinho. "Molecular radiative transport. II. Monte‐Carlo simulation." Journal of Chemical Physics 104, no. 22 (June 8, 1996): 8950–65. http://dx.doi.org/10.1063/1.471629.
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Wolf, S., and L. A. Hillenbrand. "Debris disk radiative transfer simulation tool (DDS)." Computer Physics Communications 171, no. 3 (October 2005): 208–18. http://dx.doi.org/10.1016/j.cpc.2005.04.014.
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Sheremet, Mikhail A. "Numerical Simulation of Convective-Radiative Heat Transfer." Energies 14, no. 17 (August 30, 2021): 5399. http://dx.doi.org/10.3390/en14175399.
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Heat transfer including heat conduction, thermal convection, and thermal radiation is a major transport process that occurs in various engineering and natural systems such as heat exchangers, solar collectors, nuclear reactors, atmospheric boundary layers, electronical and biomedical systems, and others [...]