Journal articles on the topic 'Synoptic transport equation'
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1
Dai, Panxi, and Ji Nie. "A Global Quasigeostrophic Diagnosis of Extratropical Extreme Precipitation." Journal of Climate 33, no. 22 (November 15, 2020): 9629–42. http://dx.doi.org/10.1175/jcli-d-20-0146.1.
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AbstractThis paper presents a global picture of the dynamic processes and synoptic characteristics of extratropical extreme precipitation events (EPEs), defined as annual maximum daily precipitation averaged over 7.5° × 7.5° regional boxes. Based on the quasigeostrophic omega equation, extreme precipitation can be decomposed into components forced by large-scale adiabatic disturbances and amplified by diabatic heating feedback. The spatial distribution of the diabatic feedback parameter is largely controlled by atmospheric precipitable water and captured by a simple model. Most spatial heterogeneities of EPEs in the middle and high latitudes are due to the spatial variations of large-scale adiabatic forcing. The adiabatic component includes the processes of vorticity advection, in which the synoptic vorticity advection by background wind dominates; temperature advection, in which the total meridional temperature advection by synoptic wind dominates; and boundary forcing. The synoptic patterns of EPEs in all extratropical regions can be classified into six clusters using the self-organizing map method: two clusters in low latitudes and four clusters in middle and high latitudes. Synoptic disturbances are characterized by strong pressure anomalies throughout the troposphere over the coastal regions and oceans and feature upper-level shortwave disturbances and a large westward tilt with height over land. Synoptic configurations favor moisture transport from ocean to land over coastal regions.
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Song, Dehai, Wen Wu, and Qiang Li. "Effects of Wave–Current Interactions on Bay–Shelf Exchange." Journal of Physical Oceanography 51, no. 5 (May 2021): 1637–54. http://dx.doi.org/10.1175/jpo-d-20-0222.1.
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AbstractBay–shelf exchange is critical to coastal systems because it promotes self-purification or pollution dilution of the systems. In this study, the effects of wave–current interactions on bay–shelf exchange are explored in a micromesotidal system—Daya Bay in southern China. Waves can enlarge the shear-induced seaward transport and reduce the residual-current-induced landward transport, which benefits the bay–shelf exchange; however, tides work oppositely and slow the wave-induced bay–shelf exchange through vertical mixing and reduced shear-induced exchange. Five wave–current interactions are compared, and it is found that the depth-dependent wave radiation stress (WRS) contributes most to the bay–shelf exchange, followed by the wave dissipation as a source term in the turbulence kinetic energy equation, and the mean current advection and refraction of wave energy (CARWE). The vertical transfer of wave-generated pressure to the mean momentum equation (also known as the form drag) and the combined wave–current bottom stress (CWCBS) play minor roles in the bay–shelf exchange. The bay–shelf exchange is faster under southerly wind than under northerly wind because the bay is facing southeast; synoptic events such as storms enhance the bay–shelf exchange. The CARWE terms are dominant in both seasonal and synoptic variations of the bay–shelf exchange because they can considerably change the distribution of significant wave height. The WRS changes the bay–shelf exchange mainly through altering the flow velocity, whereas the wave dissipation on turbulence alters the vertical mixing. The form drag and the CWCBS have little impact on the bay–shelf exchange or its seasonal and synoptic variations.
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Parazoo, N. C., A. S. Denning, S. R. Kawa, K. D. Corbin, R. S. Lokupitiya, and I. T. Baker. "Mechanisms for synoptic variations of atmospheric CO<sub>2</sub> in North America, South America and Europe." Atmospheric Chemistry and Physics 8, no. 23 (December 10, 2008): 7239–54. http://dx.doi.org/10.5194/acp-8-7239-2008.
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Abstract. Synoptic variations of atmospheric CO2 produced by interactions between weather and surface fluxes are investigated mechanistically and quantitatively in midlatitude and tropical regions using continuous in-situ CO2 observations in North America, South America and Europe and forward chemical transport model simulations with the Parameterized Chemistry Transport Model. Frontal CO2 climatologies show consistently strong, characteristic frontal CO2 signals throughout the midlatitudes of North America and Europe. Transitions between synoptically identifiable CO2 air masses or transient spikes along the frontal boundary typically characterize these signals. One case study of a summer cold front shows CO2 gradients organizing with deformational flow along weather fronts, producing strong and spatially coherent variations. In order to differentiate physical and biological controls on synoptic variations in midlatitudes and a site in Amazonia, a boundary layer budget equation is constructed to break down boundary layer CO2 tendencies into components driven by advection, moist convection, and surface fluxes. This analysis suggests that, in midlatitudes, advection is dominant throughout the year and responsible for 60–70% of day-to-day variations on average, with moist convection contributing less than 5%. At a site in Amazonia, vertical mixing, in particular coupling between convective transport and surface CO2 flux, is most important, with advection responsible for 26% of variations, moist convection 32% and surface flux 42%. Transport model sensitivity experiments agree with budget analysis. These results imply the existence of a recharge-discharge mechanism in Amazonia important for controlling synoptic variations of boundary layer CO2, and that forward and inverse simulations should take care to represent moist convective transport. Due to the scarcity of tropical observations at the time of this study, results in Amazonia are not generalized for the tropics, and future work should extend analysis to additional tropical locations.
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Markkanen, Johannes, and Jessica Agarwal. "Scattering, absorption, and thermal emission by large cometary dust particles: Synoptic numerical solution." Astronomy & Astrophysics 631 (November 2019): A164. http://dx.doi.org/10.1051/0004-6361/201936235.
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Context. Remote light scattering and thermal infrared observations provide clues about the physical properties of cometary and interplanetary dust particles. Identifying these properties will lead to a better understanding of the formation and evolution of the Solar System. Aims. We present a numerical solution for the radiative and conductive heat transport in a random particulate medium enclosed by an arbitrarily shaped surface. The method will be applied to study thermal properties of cometary dust particles. Methods. The recently introduced incoherent Monte Carlo radiative transfer method developed for scattering, absorption, and propagation of electromagnetic waves in dense discrete random media is extended for radiative heat transfer and thermal emission. The solution is coupled with the conductive Fourier transport equation that is solved with the finite-element method. Results. The proposed method allows the synoptic analysis of light scattering and thermal emission by large cometary dust particles consisting of submicrometer-sized grains. In particular, we show that these particles can sustain significant temperature gradients resulting in the superheating factor phase function observed for the coma of comet 67P/Churyumov–Gerasimenko.
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Parazoo, N., A. Denning, S. Kawa, K. Corbin, R. Lokupitiya, and I. Baker. "Mechanisms for synoptic transport of atmospheric CO<sub>2</sub> in the midlatitudes and tropics." Atmospheric Chemistry and Physics Discussions 8, no. 3 (June 20, 2008): 12197–225. http://dx.doi.org/10.5194/acpd-8-12197-2008.
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Abstract. Synoptic variations of CO2 mixing ratio produced by interactions between weather and surface fluxes are investigated mechanistically and quantitatively in midlatitude and tropical regions using continuous in-situ CO2 observations in North America, South America and Europe and forward chemical transport model simulations with the Parameterized Chemistry Transport Model. Frontal CO2 climatologies show consistently strong, characteristic frontal CO2 signals throughout the midlatitudes of North America and Europe. Transitions between synoptically identifiable CO2 air masses or transient spikes along the frontal boundary typically characterize these signals. One case study of a summer cold front shows that CO2 gradients organize with deformational flow along weather fronts producing strong and spatially coherent variations. A boundary layer budget equation is constructed in order to determine contributions to boundary layer CO2 tendencies by horizontal and vertical advection, moist convection, and biological and anthropogenic surface fluxes. Analysis of this equation suggests that, in midlatitudes, advection is responsible for 50–90% of the amplitude of frontal variations in the summer, depending on upstream influences, and 50% of all day-to-day variations throughout the year. Simulations testing sensitivity to local cloud and surface fluxes further suggest that horizontal advection is a major source of CO2 variability in midlatitudes. In the tropics, coupling between convective transport and surface CO2 flux is most important. Due to the scarcity of tropical observations available at the time of this study, future work should extend such mechanistic analysis to additional tropical locations.
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Ancona, M. G. "Hydrodynamic Models of Semiconductor Electron Transport at High Fields." VLSI Design 3, no. 2 (January 1, 1995): 101–14. http://dx.doi.org/10.1155/1995/85107.
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Hydrodynamic or continuum descriptions of electron transport have long been used for modeling and simulating semiconductor devices. In this paper, we use classical field theory ideas to discuss the physical foundations of such descriptions as applied specifically to high-field transport regimes. The classical field theory development of these types of models is of interest because it differs significantly from and may be viewed as complementary to conventional derivations based on the Boltzmann equation: After outlining the general field theoretic principles upon which our development of fluid-based high-field transport descriptions is based, we study several specific models both analytically and using numerical simulation. These models provide an overall framework for understanding and extending various theories which have appeared in the literature. Most importantly, they emphasize the importance of including memory or history effects and viscosity in describing high-field transport. In all of this our aim is a unified and synoptic view unencumbered with microscopic details. Obtaining quantitative agreement with specific experiments and/or microscopic simulations is only of secondary importance. We share the view that continuum approaches can provide succinct and computationally-efficient models needed for current and future semiconductor device analysis and engineering. At the same time, we believe that these models need not be phenomenological but can be given solid physical foundation in macroscopic principles.
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Chen, Baode, Wen-wen Tung, and Michio Yanai. "Multiscale Temporal Mean Features of Perturbation Kinetic Energy and Its Budget in the Tropics: Review and Computation." Meteorological Monographs 56 (May 1, 2016): 8.1–8.23. http://dx.doi.org/10.1175/amsmonographs-d-15-0017.1.
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Abstract The authors examined the maintenance mechanisms of perturbation kinetic energy (PKE) in the tropical regions for multiple time scales by computing and analyzing its budget equation. The emphasis has been placed on the mean features of synoptic and subseasonal variabilities using a 33-yr dataset. From analysis of the contributions from u-wind and υ-wind components, the PKE maximum in the Indian Ocean is attributed less to synoptic variability and more to intraseasonal variability in which the Madden–Julian oscillation (MJO) dominates; however, there is strong evidence of seasonal variability affiliated with the Asian monsoon systems. The ones in the eastern Pacific and Atlantic Oceans are closely related to both intraseasonal and synoptic variability that result from the strong MJO and the relatively large amplitude of equatorial waves. The maintenance of the PKE budget mainly depends on the structure of time mean horizontal flows, the location of convection, and the transport of PKE from the extratropics. In the regions with strong convective activities, such as the eastern Indian Ocean to the western Pacific, the production of PKE occurs between 700 and 200 hPa at the expense of perturbation available potential energy (PAPE), which is generated by convective heating. This gain in PKE is largely offset by divergence of the geopotential component of vertical energy flux; that is, it is redistributed to the upper- and lower-atmospheric layers by the pressure field. Strong PKE generation through the horizontal convergence of the extratropical energy flux takes place in the upper troposphere over the eastern Pacific and Atlantic Ocean, and is largely balanced by a PKE loss due to barotropic conversion, which is determined solely by the sign of longitudinal stretching deformation. However, over the Indian Ocean, there is a net PKE loss due to divergence of energy flux, which is compensated by PKE gain through the shear generation.
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Belikov, D., S. Maksyutov, T. Miyasaka, T. Saeki, R. Zhuravlev, and B. Kiryushov. "Mass-conserving tracer transport modelling on a reduced latitude-longitude grid." Geoscientific Model Development Discussions 3, no. 4 (October 20, 2010): 1737–81. http://dx.doi.org/10.5194/gmdd-3-1737-2010.
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Abstract. The need to perform long-term simulations with reasonable accuracy has led to the development of mass-conservative and efficient numerical methods for solving the transport equation in forward and inverse models. We designed and implemented a flux-form (Eulerian) tracer transport algorithm in the National Institute for Environmental Studies Transport Model (NIES TM), which is used for simulating diurnal and synoptic-scale variations of tropospheric long-lived constituents, as well as their seasonal and inter-annual variability. Implementation of the flux-form method requires the mass conservative wind fields. However, the model is off-line and is driven by datasets from a global atmospheric model or data assimilation system, in which vertically integrated mass changes are not in balance with the surface pressure tendency and mass conservation is not achieved. To rectify the mass-imbalance, a flux-correction method is employed. To avoid singularity near the poles caused by the small grid size arising from the meridional convergence problem, the proposed model uses a reduced latitude-longitude grid scheme, in which the grid size is doubled several times approaching the poles. This approach overcomes the Courant condition in the Polar Regions, maintains a reasonably high integration time-step and ensures adequate model performance during simulations. To assess the model performance, we performed global transport simulations for SF6, 222Rn and CO2. The results were compared with observations available from the World Data Centre for Greenhouse Gases, GLOBALVIEW and the Hateruma monitoring station, Japan. Overall, the results show that the proposed flux-form version of NIES TM can produce tropospheric tracer transport more realistically than previously possible. The reasons for this improvement are discussed.
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Belikov, D., S. Maksyutov, T. Miyasaka, T. Saeki, R. Zhuravlev, and B. Kiryushov. "Mass-conserving tracer transport modelling on a reduced latitude-longitude grid with NIES-TM." Geoscientific Model Development 4, no. 1 (March 22, 2011): 207–22. http://dx.doi.org/10.5194/gmd-4-207-2011.
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Abstract. The need to perform long-term simulations with reasonable accuracy has led to the development of mass-conservative and efficient numerical methods for solving the transport equation in forward and inverse models. We designed and implemented a flux-form (Eulerian) tracer transport algorithm in the National Institute for Environmental Studies Transport Model (NIES TM), which is used for simulating diurnal and synoptic-scale variations of tropospheric long-lived constituents, as well as their seasonal and inter-annual variability. Implementation of the flux-form method requires the mass conservative wind fields. However, the model is off-line and is driven by datasets from a global atmospheric model or data assimilation system, in which vertically integrated mass changes are not in balance with the surface pressure tendency and mass conservation is not achieved. To rectify the mass-imbalance, a flux-correction method is employed. To avoid a singularity near the poles, caused by the small grid size arising from the meridional convergence problem, the proposed model uses a reduced latitude–longitude grid scheme, in which the grid size is doubled several times approaching the poles. This approach overcomes the Courant condition in the Polar Regions, maintains a reasonably high integration time-step, and ensures adequate model performance during simulations. To assess the model performance, we performed global transport simulations for SF6, 222Rn, and CO2. The results were compared with observations available from the World Data Centre for Greenhouse Gases, GLOBALVIEW, and the Hateruma monitoring station, Japan. Overall, the results show that the proposed flux-form version of NIES TM can produce tropospheric tracer transport more realistically than previously possible. The reasons for this improvement are discussed.
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Khouider, Boualem, Ying Han, Andrew J. Majda, and Samuel N. Stechmann. "Multiscale Waves in an MJO Background and Convective Momentum Transport Feedback." Journal of the Atmospheric Sciences 69, no. 3 (March 1, 2012): 915–33. http://dx.doi.org/10.1175/jas-d-11-0152.1.
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Abstract The authors use linear analysis for a simple model to study the evolution of convectively coupled waves (CCWs) in a background shear and background moisture mimicking the observed structure of the Madden–Julian oscillation (MJO). This is motivated by the observation, in an idealized setting, of intraseasonal two-way interactions between CCWs and a background wind. It is found here that profiles with a bottom-heavy moisture content are more favorable to the development of mesoscale/squall line–like waves whereas synoptic-scale CCWs are typically more sensitive to the shear strength. The MJO envelope is thus divided into three regions, in terms of the types of CCWs that are favored: an onset region in front that is favorable to Kelvin waves, a mature or active region in the middle in which squall lines are prominent, and the stratiform and decay phase region in the back that is favorable to westward inertia–gravity (WIG) waves. A plausible convective momentum transport (CMT) feedback is then provided according to the results of the idealized two-way interaction model. The active region, in particular, coincides with the westerly wind burst where both Kelvin waves and squall lines are believed to play a significant role in both the deceleration of low-/high-level easterly/westerly winds and the acceleration of low-/high-level westerly/easterly winds. The WIG waves in the wake could be a precursor for a subsequent MJO event through the acceleration of low-/high-level easterly/westerly winds, which in turn favor Kelvin waves, and the cycle repeats. These results open interesting directions for future studies using observations and/or detailed numerical simulations using the full primitive equation.
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Wang, An-Hsiang, Chung-Chieh Wang, and George Tai-Jen Chen. "A Study on Synoptic Conditions Leading to the Extreme Rainfall in Taiwan during 10–12 June 2012." Atmosphere 12, no. 10 (September 27, 2021): 1255. http://dx.doi.org/10.3390/atmos12101255.
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During 10–12 June 2012, heavy rainfall occurred three days in a row in southern and central Taiwan, with daily rainfall maxima exceeding 500 mm on each day. In the Mei-yu season (May–June) during 1993–2000, only two other rainfall events had a comparable amount and duration, but this case was the only one that occurred well before the arrival of the Mei-yu front. The synoptic conditions and their evolution leading to this unique event are thus important and are the foci of this study. Our analysis indicates that the 10–12 June 2012 event in Taiwan was caused by the strong and persistent west-southwesterly low-level jet (LLJ) that transported warm, moist, and unstable air from upstream and then impinged on the island. The LLJ developed due to the enhanced horizontal pressure (or height) gradient when the pressure at low-levels fell significantly (by ~8 hPa) in South China (north of the jet) during 8–10 June, but the subtropical high to the southeast maintained its strength. Further, through a diagnosis using the pressure tendency equation, it is found that both warm air advection and the dynamic effects (column divergence and transport of mass by vertical motion) contributed to the pressure fall in South China. The warm air advection occurred in the southern part of a large-scale confluent pattern in China, and the persistent west-southwesterly flow through deep layer (mainly above 800 hPa) in South China transported warmer and less dense air into the region from lower latitudes. On the other hand, South China was also located under the diffluent zone in the northeastern quadrant of the South Asian upper-level anticyclone, which strengthened during 5–10 June and provided divergence aloft, which exceeded the low-level convergence and upward transport of mass (at a fixed height) into the column by vertical motion on 9 June. As a result, the dynamic effects also contributed to the pressure fall, although secondary to the warm air advection. The destabilization process in South China during 8–10 June was also helpful to increase convective activity and upper-level divergence.
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Seo, Jihoon, Doo-Sun R. Park, Jin Young Kim, Daeok Youn, Yong Bin Lim, and Yumi Kim. "Effects of meteorology and emissions on urban air quality: a quantitative statistical approach to long-term records (1999–2016) in Seoul, South Korea." Atmospheric Chemistry and Physics 18, no. 21 (November 9, 2018): 16121–37. http://dx.doi.org/10.5194/acp-18-16121-2018.
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Abstract. Together with emissions of air pollutants and precursors, meteorological conditions play important roles in local air quality through accumulation or ventilation, regional transport, and atmospheric chemistry. In this study, we extensively investigated multi-timescale meteorological effects on the urban air pollution using the long-term measurements data of PM10, SO2, NO2, CO, and O3 and meteorological variables over the period of 1999–2016 in Seoul, South Korea. The long-term air quality data were decomposed into trend-free short-term components and long-term trends by the Kolmogorov–Zurbenko filter, and the effects of meteorology and emissions were quantitatively isolated using a multiple linear regression with meteorological variables. In terms of short-term variability, intercorrelations among the pollutants and meteorological variables and composite analysis of synoptic meteorological fields exhibited that the warm and stagnant conditions in the migratory high-pressure system are related to the high PM10 and primary pollutant, while the strong irradiance and low NO2 by high winds at the rear of a cyclone are related to the high O3. In terms of long-term trends, decrease in PM10 (−1.75 µg m−3 yr−1) and increase in O3 (+0.88 ppb yr−1) in Seoul were largely contributed by the meteorology-related trends (−0.94 µg m−3 yr−1 for PM10 and +0.47 ppb yr−1 for O3), which were attributable to the subregional-scale wind speed increase. Comparisons with estimated local emissions and socioeconomic indices like gross domestic product (GDP) growth and fuel consumptions indicate probable influences of the 2008 global economic recession as well as the enforced regulations from the mid-2000s on the emission-related trends of PM10 and other primary pollutants. Change rates of local emissions and the transport term of long-term components calculated by the tracer continuity equation revealed a decrease in contributions of local emissions to the primary pollutants including PM10 and an increase in contributions of local secondary productions to O3. The present results not only reveal an important role of synoptic meteorological conditions on the episodic air pollution events but also give insights into the practical effects of environmental policies and regulations on the long-term air pollution trends. As a complementary approach to the chemical transport modeling, this study will provide a scientific background for developing and improving effective air quality management strategy in Seoul and its metropolitan area.
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M K, AL-MUTAIRI, and BASSET H ABDEL. "Diagnostic study of diabatic heating and potential vorticity during a case of cyclogenesis." MAUSAM 71, no. 2 (August 3, 2021): 255–74. http://dx.doi.org/10.54302/mausam.v71i2.24.
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On 16-17 November, 2015, north and middle regions of Saudi Arabia were hit by a case of cyclogenesisassociated with heavy rainfall. This work presents a diagnostic study of this heavy rainfallcase based on the analysis of diabatic heating and potential vorticity. The synoptic analysis investigate that the important dynamical factors that causes this case are the northward extension of Red Sea Trough, anticyclone over the Arabian Peninsula, a travailing midlatitude upper trough, moisture transport pathways and strong upward motion arising from tropospheric instability. The calculation of diabatic heating by the thermodynamic equation illustrate that the contribution of vertical temperature advection and the adiabatic term are opposite to each other during the period of study. The largest contribution of the horizontal cold advection occurs during the first two days while the largest contribution of the horizontal warm advection occurs during the maximum development days. The dynamics of the studied case are also investigated in terms of isobaric Potential Vorticity. It is found that the location of the low-level Potential Vorticity anomaly and the Potential Vorticity generation estimates coincides with the heating region, which implies that condensation supports a large enough source to explain the existence of the low-level Potential Vorticity anomaly.
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Yang, Long, Maofeng Liu, James A. Smith, and Fuqiang Tian. "Typhoon Nina and the August 1975 Flood over Central China." Journal of Hydrometeorology 18, no. 2 (January 31, 2017): 451–72. http://dx.doi.org/10.1175/jhm-d-16-0152.1.
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Abstract The August 1975 flood in central China was one of the most destructive floods in history. Catastrophic flooding was the product of extreme rainfall from Typhoon Nina over a 3-day period from 5 to 7 August 1975. Despite the prominence of the August 1975 flood, relatively little is known about the evolution of rainfall responsible for the flood. Details of extreme rainfall and flooding for the August 1975 event in central China are examined based on empirical analyses of rainfall and streamflow measurements and based on downscaling simulations using the Weather Research and Forecasting (WRF) Model, driven by Twentieth Century Reanalysis (20CR) fields. Key hydrometeorological features of the flood event are placed in a climatological context through hydroclimatological analyses of 20CR fields. Results point to the complex evolution of rainfall over the 3-day period with distinctive periods of storm structure controlling rainfall distribution in the flood region. Blocking plays a central role in controlling anomalous storm motion of Typhoon Nina and extreme duration of heavy rainfall. Interaction of Typhoon Nina with a second tropical depression played a central role in creating a zone of anomalously large water vapor transport, a central feature of heavy rainfall during the critical storm period on 7 August. Analyses based on the quasigeostrophic omega equation identified the predominant role of warm air advection for synoptic-scale vertical motion. Back-trajectory analyses using a Lagrangian parcel tracking algorithm are used to assess and quantify water vapor transport for the flood. The analytical framework developed in this study is designed to improve hydrometeorological approaches for flood-control design.
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Lane, LJ, KG Renard, GR Foster, and JM Laflen. "Development and application of modern soil erosion prediction technology - The USDA experience." Soil Research 30, no. 6 (1992): 893. http://dx.doi.org/10.1071/sr9920893.
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Erosion prediction efforts are described to provide a synopsis of the USDA's experience in developing and applying soil erosion prediction technology in its research and development activities and its soil conservation programs. For almost five decades, equations to predict soil erosion by water have been useful m developing plans for controlling soil erosion and sedimentation. The Universal Soil Low Equation (USLE) is the most widely known and used of the erosion prediction equations. The USLE presents a simply understood and easily applied technology which has been of incalculable benefit to soil conservation and land management. The Chemicals, Runoff, and Erosion from Agricultural Management Systems Model (CREAMS) contains a sophisticated erosion component based, in part, on the USLE and on flow hydraulics and the processes of sediment detachment, transport, and deposition. In 1985, the USDA in cooperation with BLM and several universities initiated a national project called the Water Erosion Prediction Project (WEPP) to develop a next generation water erosion prediction technology. The Revised Universal Soil Loss Equation (RUSLE) is an update of the USLE to improve erosion prediction in the interim before WEPP is adopted and to provide and adjunct technology thereafter.
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Majda, Andrew J. "New Multiscale Models and Self-Similarity in Tropical Convection." Journal of the Atmospheric Sciences 64, no. 4 (April 1, 2007): 1393–404. http://dx.doi.org/10.1175/jas3880.1.
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Abstract One of the unexplained striking features of tropical convection is the observed statistical self-similarity in clusters, superclusters, and intraseasonal oscillations through complex multiscale processes ranging from the mesoscales to the equatorial synoptic scales to the intraseasonal/planetary scales. Here new multispatial-scale, multitime-scale, simplified asymptotic models are derived systematically from the equatorial primitive equations on the range of scales from mesoscale to equatorial synoptic to planetary/intraseasonal, which provide a useful analytic framework for addressing these issues. New mesoscale equatorial synoptic dynamical (MESD) models and balanced MESD (BMESD) models are developed for the multitime, multispace interaction from mesoscales to equatorial synoptic scales; new multitime versions of the intraseasonal planetary equatorial synoptic dynamics (IPESD) models are developed for multiple spatiotemporal interactions on equatorial synoptic scales and planetary scales. The mathematical character derived below for all these simplified models explicitly demonstrates that the main nonlinear interactions across scales are quasi-linear where eddy flux divergences of momentum and temperature from nonlinear advection from the smaller-scale spatiotemporal flows as well as mean source effects accumulate in time and drive the waves on the successively larger spatiotemporal scales. Furthermore, these processes that transfer energy to the next larger, longer, spatiotemporal scales are self-similar in a suitable sense established here. On the other hand, the larger scales set the environment for this transport through processes such as mean advection of the smaller scales.
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Chhiber, Rohit, Arcadi V. Usmanov, William H. Matthaeus, and Melvyn L. Goldstein. "Large-scale Structure and Turbulence Transport in the Inner Solar Wind: Comparison of Parker Solar Probe’s First Five Orbits with a Global 3D Reynolds-averaged MHD Model." Astrophysical Journal 923, no. 1 (December 1, 2021): 89. http://dx.doi.org/10.3847/1538-4357/ac1ac7.
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Abstract Simulation results from a global magnetohydrodynamic model of the solar corona and solar wind are compared with Parker Solar Probe (PSP) observations during its first five orbits. The fully three-dimensional model is based on Reynolds-averaged mean-flow equations coupled with turbulence-transport equations. The model includes the effects of electron heat conduction, Coulomb collisions, turbulent Reynolds stresses, and heating of protons and electrons via a turbulent cascade. Turbulence-transport equations for average turbulence energy, cross helicity, and correlation length are solved concurrently with the mean-flow equations. Boundary conditions at the coronal base are specified using solar synoptic magnetograms. Plasma, magnetic field, and turbulence parameters are calculated along the PSP trajectory. Data from the first five orbits are aggregated to obtain trends as a function of heliocentric distance. Comparison of simulation results with PSP data shows good agreement, especially for mean-flow parameters. Synthetic distributions of magnetic fluctuations are generated, constrained by the local rms turbulence amplitude given by the model. Properties of this computed turbulence are compared with PSP observations.
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Waite, Michael L., and Boualem Khouider. "Boundary Layer Dynamics in a Simple Model for Convectively Coupled Gravity Waves." Journal of the Atmospheric Sciences 66, no. 9 (September 1, 2009): 2780–95. http://dx.doi.org/10.1175/2009jas2871.1.
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Abstract A simplified model of intermediate complexity for convectively coupled gravity waves that incorporates the bulk dynamics of the atmospheric boundary layer is developed and analyzed. The model comprises equations for velocity, potential temperature, and moist entropy in the boundary layer as well as equations for the free tropospheric barotropic (vertically uniform) velocity and first two baroclinic modes of vertical structure. It is based on the multicloud model of Khouider and Majda coupled to the bulk boundary layer–shallow cumulus model of Stevens. The original multicloud model has a purely thermodynamic boundary layer and no barotropic velocity mode. Here, boundary layer horizontal velocity divergence is matched with barotropic convergence in the free troposphere and yields environmental downdrafts. Both environmental and convective downdrafts act to transport dry midtropospheric air into the boundary layer. Basic states in radiative–convective equilibrium are found and are shown to be consistent with observations of boundary layer and free troposphere climatology. The linear stability of these basic states, in the case without rotation, is then analyzed for a variety of tropospheric regimes. The inclusion of boundary layer dynamics—specifically, environmental downdrafts and entrainment of free tropospheric air—enhances the instability of both the synoptic-scale moist gravity waves and nonpropagating congestus modes in the multicloud model. The congestus mode has a preferred synoptic-scale wavelength, which is absent when a purely thermodynamic boundary layer is employed. The weak destabilization of a fast mesoscale wave, with a phase speed of 26 m s−1 and coupling to deep convection, is also discussed.
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Ferreira, David, John Marshall, and Brian Rose. "Climate Determinism Revisited: Multiple Equilibria in a Complex Climate Model." Journal of Climate 24, no. 4 (February 15, 2011): 992–1012. http://dx.doi.org/10.1175/2010jcli3580.1.
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Abstract Multiple equilibria in a coupled ocean–atmosphere–sea ice general circulation model (GCM) of an aquaplanet with many degrees of freedom are studied. Three different stable states are found for exactly the same set of parameters and external forcings: a cold state in which a polar sea ice cap extends into the midlatitudes; a warm state, which is ice free; and a completely sea ice–covered “snowball” state. Although low-order energy balance models of the climate are known to exhibit intransitivity (i.e., more than one climate state for a given set of governing equations), the results reported here are the first to demonstrate that this is a property of a complex coupled climate model with a consistent set of equations representing the 3D dynamics of the ocean and atmosphere. The coupled model notably includes atmospheric synoptic systems, large-scale circulation of the ocean, a fully active hydrological cycle, sea ice, and a seasonal cycle. There are no flux adjustments, with the system being solely forced by incoming solar radiation at the top of the atmosphere. It is demonstrated that the multiple equilibria owe their existence to the presence of meridional structure in ocean heat transport: namely, a large heat transport out of the tropics and a relatively weak high-latitude transport. The associated large midlatitude convergence of ocean heat transport leads to a preferred latitude at which the sea ice edge can rest. The mechanism operates in two very different ocean circulation regimes, suggesting that the stabilization of the large ice cap could be a robust feature of the climate system. Finally, the role of ocean heat convergence in permitting multiple equilibria is further explored in simpler models: an atmospheric GCM coupled to a slab mixed layer ocean and an energy balance model.
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Moshonkin, S. N., and N. A. Diansky. "Upper mixed layer temperature anomalies at the North Atlantic storm-track zone." Annales Geophysicae 13, no. 10 (October 31, 1995): 1015–26. http://dx.doi.org/10.1007/s00585-995-1015-x.
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Abstract. Synoptic sea surface temperature anomalies (SSTAs) were determined as a result of separation of time scales smaller than 183 days. The SSTAs were investigated using daily data of ocean weather station "C" (52.75°N; 35.5°W) from 1 January 1976 to 31 December 1980 (1827 days). There were 47 positive and 50 negative significant SSTAs (lifetime longer than 3 days, absolute value greater than 0.10 °C) with four main intervals of the lifetime repetitions: 1. 4–7 days (45% of all cases), 2. 9–13 days (20–25%), 3. 14–18 days (10–15%), and 4. 21–30 days (10–15%) and with a magnitude 1.5–2.0 °C. An upper layer balance model based on equations for temperature, salinity, mechanical energy (with advanced parametrization), state (density), and drift currents was used to simulate SSTA. The original method of modelling taking into account the mean observed temperature profiles proved to be very stable. The model SSTAs are in a good agreement with the observed amplitudes and phases of synoptic SSTAs during all 5 years. Surface heat flux anomalies are the main source of SSTAs. The influence of anomalous drift heat advection is about 30–50% of the SSTA, and the influence of salinity anomalies is about 10–25% and less. The influence of a large-scale ocean front was isolated only once in February-April 1978 during all 5 years. Synoptic SSTAs develop just in the upper half of the homogeneous layer at each winter. We suggest that there are two main causes of such active sublayer formation: 1. surface heat flux in the warm sectors of cyclones and 2. predominant heat transport by ocean currents from the south. All frequency functions of the ocean temperature synoptic response to heat and momentum surface fluxes are of integral character (red noise), though there is strong resonance with 20-days period of wind-driven horizontal heat advection with mixed layer temperature; there are some other peculiarities on the time scales from 5.5 to 13 days. Observed and modelled frequency functions seem to be in good agreement.
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Schnitzer, Ory, and Ehud Yariv. "The Taylor–Melcher leaky dielectric model as a macroscale electrokinetic description." Journal of Fluid Mechanics 773 (May 14, 2015): 1–33. http://dx.doi.org/10.1017/jfm.2015.242.
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While the Taylor–Melcher electrohydrodynamic model entails ionic charge carriers, it addresses neither ionic transport within the liquids nor the formation of diffuse space-charge layers about their common interface. Moreover, as this model is hinged upon the presence of non-zero interfacial-charge density, it appears to be in contradiction with the aggregate electro-neutrality implied by ionic screening. Following a brief synopsis published by Baygents & Saville (Third International Colloquium on Drops and Bubbles, AIP Conference Proceedings, vol. 7, 1989, American Institute of Physics, pp. 7–17) we systematically derive here the macroscale description appropriate for leaky dielectric liquids, starting from the primitive electrokinetic equations and addressing the double limit of thin space-charge layers and strong fields. This derivation is accomplished through the use of matched asymptotic expansions between the narrow space-charge layers adjacent to the interface and the electro-neutral bulk domains, which are homogenized by the strong ionic advection. Electrokinetic transport within the electrical ‘triple layer’ comprising the genuine interface and the adjacent space-charge layers is embodied in effective boundary conditions; these conditions, together with the simplified transport within the bulk domains, constitute the requisite macroscale description. This description essentially coincides with the familiar equations of Melcher & Taylor (Annu. Rev. Fluid Mech., vol. 1, 1969, pp. 111–146). A key quantity in our macroscale description is the ‘apparent’ surface-charge density, provided by the transversely integrated triple-layer microscale charge. At leading order, this density vanishes due to the expected Debye-layer screening; its asymptotic correction provides the ‘interfacial’ surface-charge density appearing in the Taylor–Melcher model. Our unified electrohydrodynamic treatment provides a reinterpretation of both the Taylor–Melcher conductivity-ratio parameter and the electrical Reynolds number. The latter, expressed in terms of fundamental electrokinetic properties, becomes $O(1)$ only for intense applied fields, comparable with the transverse field within the space-charge layers; at this limit the asymptotic scheme collapses. Surface-charge advection is accordingly absent in the macroscale description. Owing to the inevitable presence of (screened) net charge on the genuine interface, the drop also undergoes electrophoretic motion. The associated flow, however, is asymptotically smaller than that corresponding to the Taylor–Melcher circulation. Our successful matching procedure contrasts the analysis of Baygents & Saville, who considered more general electrolytes and were unable to directly match the inner and outer regions. We discuss this difference in detail.
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Princevac, M., J. C. R. Hunt, and H. J. S. Fernando. "Quasi-Steady Katabatic Winds on Slopes in Wide Valleys: Hydraulic Theory and Observations." Journal of the Atmospheric Sciences 65, no. 2 (February 1, 2008): 627–43. http://dx.doi.org/10.1175/2007jas2110.1.
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Abstract Theoretical and field observational studies on mean velocity and temperature fields of quasi-steady nocturnal downslope (katabatic) flows on sloping surfaces are reported for the case of very wide valleys in the presence of weak synoptic winds. Because of the lateral constraints on the flow, Coriolis effects are considered negligible. The layer-averaged equations of Manins and Sawford were used for the analysis. It is shown that (i) in the absence of significant turbulent entrainment into the current (i.e., at large Richardson numbers Ri = Δh cosα/U2) the downslope flow velocity U is related to the slope length (LH), slope angle (α), and the buoyancy jump between the current and the background atmosphere (Δ) as U = λu(ΔLH sinα)1/2, where λu is a constant and h is the flow depth; (ii) on very long slopes h is proportional to Lh(tanα)1/2; and (iii) under highly stable conditions (i.e., Ri > 1) the katabatic flow exhibits pulsations with period T0 = 2π/N sinα, where N is the buoyancy frequency of the background atmosphere. These predictions are verified principally using observations made during the Vertical Transport and Mixing Experiment (VTMX) conducted in Salt Lake City, Utah, in October 2000. By assuming the flow follows a straight line trajectory to the nearest ridgeline a good agreement was found between the predictions and observations over appropriate Richardson number ranges. For Ri > 1.5, λu ≈ 0.2, although λu was a decreasing function of Ri at lesser stabilities. Oscillations with period T0 are simply alongslope (critical) internal-wave oscillations with a slope-normal wavenumber, which are liable for degeneration into turbulence during their reflection. These critical internal waves may be responsible, at least partly, for weak sustained turbulence often observed in complex-terrain nocturnal boundary layer flows.
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Sun, Pengfei, Ruimei Cheng, Wenfa Xiao, Lixiong Zeng, Yafei Shen, Lijun Wang, Tian Chen, and Meng Zhang. "The Relationship between Ectomycorrhizal Fungi, Nitrogen Deposition, and Pinus massoniana Seedling Nitrogen Transporter Gene Expression and Nitrogen Uptake Kinetics." Journal of Fungi 9, no. 1 (December 31, 2022): 65. http://dx.doi.org/10.3390/jof9010065.
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Analyzing the molecular and physiological processes that govern the uptake and transport of nitrogen (N) in plants is central to efforts to fully understand the optimization of plant N use and the changes in the N-use efficiency in relation to changes in atmospheric N deposition changes. Here, a field experiment was conducted using the ectomycorrhizal fungi (EMF), Pisolithus tinctorius (Pt) and Suillus grevillei (Sg). The effects of N deposition were investigated using concentrations of 0 kg·N·hm−2a−1 (N0), a normal N deposition of 30 kg·N·hm−2a−1 (N30), a moderate N deposition of 60 kg·N·hm−2a−1 (N60), and a severe N deposition of 90 kg·N·hm−2a−1 (N90), with the goal of examining how these factors impacted root activity, root absorbing area, NH4+ and NO3− uptake kinetics, and the expression of ammonium and nitrate transporter genes in Pinus massoniana seedlings under different levels of N deposition. These data revealed that EMF inoculation led to increased root dry weight, activity, and absorbing area. The NH4+ and NO3− uptake kinetics in seedlings conformed to the Michaelis–Menten equation, and uptake rates declined with increasing levels of N addition, with NH4+ uptake rates remaining higher than NO3− uptake rates for all tested concentrations. EMF inoculation was associated with higher Vmax values than were observed for non-mycorrhizal plants. Nitrogen addition resulted in the upregulation of genes in the AMT1 family and the downregulation of genes in the NRT family. EMF inoculation under the N60 and N90 treatment conditions resulted in the increased expression of each of both these gene families. NH4+ and NO3− uptake kinetics were also positively correlated with associated transporter gene expression in P. massoniana roots. Together, these data offer a theoretical foundation for EMF inoculation under conditions of increased N deposition associated with climate change in an effort to improve N absorption and transport rates through the regulation of key nitrogen transporter genes, thereby enhancing N utilization efficiency and promoting plant growth. Synopsis: EMF could enhance the efficiency of N utilization and promote the growth of Pinus massoniana under conditions of increased N deposition.
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陳冠杰, 陳冠杰, and 鄒治華 Kuan-Chieh Chen. "尺度交互作用對夏與秋季颱風強度發展之影響." 大氣科學 50, no. 2 (July 2022): 151–87. http://dx.doi.org/10.53106/025400022022075002003.
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<p>本研究利用綜觀尺度擾動(SSE)動能方程式，定量分析尺度交互作用對颱風強度發展的影響。研究結果發現，強烈颱風(C3-C5等級，最大強度≥96 knots)的移動速度(發展時間)較弱颱風(C1-C2等級，最大強度64~95 knots)慢(長)，增強率較大。分析強颱移動速度較慢的原因，發現弱颱風與強烈颱風主要受到大尺度副高環流場的導引而移動。然而，強颱伴隨的駛流場較弱，其可能與副高環流場減弱及季風槽和季內震盪(ISO)氣旋式環流的增強有關。此外，強(弱)颱往西北方向(往西以及往北轉向)移動。而強颱增強率較強的原因為其東南-西北向的移動路徑，經過西北太平洋海溫最高、對流層頂溫度最低、垂直風切場最弱，以及ISO擾動動能最大的區域，有利強颱的強度發展。</p> <p>SSE動能方程式的研究結果顯示，在颱風從生成增強至最大強度的過程中，正壓能量轉換(CK項)與斜壓能量轉換(CE項)均是颱風強度增強的能量來源。CK項中的CKS-M 和CKS-ISO兩項均有正貢獻，即季節平均環流與ISO均傳送能量給颱風發展。然而，在颱風發展後期，強颱與弱颱CKS-ISO差異大，強颱自ISO 獲得較多能量。CKS-ISO差異主要來源為CKS-ISO中的-(〖u_s^’ v〗_s^’ (∂u_I^’)/∂y) ̅ 項，該項與強颱伴隨ISO氣旋式環流(-(∂u_I^’)/∂y>0)的增強及強颱 〖u_s^’ v〗_s^’向北傳送動量較多有關。因此，當ISO與颱風增強，強颱將自ISO 獲得更多能量。此外，因強颱與伴隨強颱的ISO氣旋式環流移速較慢，在颱風發展後期，強颱與ISO氣旋式環流仍位在暖洋面上。而ISO氣旋式環流南側西南氣流所提供的水氣，亦有利強颱的潛熱釋放，將強颱可用位能轉換成更多的強颱動能。此正回饋效應，使強颱得到較多能量而強度較強。因此，尺度交互作用是颱風強度發展的重要機制。</p> <p> </p><p>This study quantitatively analyzed the influence of scale interaction on typhoon intensity by using the synoptic-scale eddy (SSE) kinetic energy equation. Our research showed that speed of movement, development time, and intensification rate of intense typhoons (categories 3–5 with maximum sustained wind speeds greater than 96 knots) are slower, longer, and larger, respectively, than those of weak typhoons (categories 1–2 with maximum sustained wind speeds between 64 and 95 knots). By analyzing the reasons for the slower speed of movement of intense typhoons, we discovered that weak and intense typhoons are mainly steered by large-scale subtropical high circulation during the intensification process. However, the steering flow of intense typhoons are much weaker which may result from the weakened subtropical high circulation, the enhanced monsoon trough and strengthened intraseasonal oscillation (ISO) cyclonic circulation. In addition, intense typhoons were steered northwestward, while weak typhoons moved westward or northward recurving. The northwestward propagation of intense typhoons experienced the highest sea surface temperature (SST), lowest tropopause temperature, weakest vertical wind shear, and largest ISO kinetic energy region over the western North Pacific (WNP). These large-scale environments were favorable for the growth (a larger intensification rate) of intense typhoons.</p> <p>Further diagnosis of the SSE kinetic energy budget suggested that the enhancement of typhoon intensity is contributed by both barotropic (CK) and baroclinic (CE) energy conversions during the intensification process. The positive contributions of CKS-M and CKS-ISO in the CK term indicate that both seasonal mean circulation and ISO flow provide energy to typhoons. However, intense typhoons gain more eddy kinetic energy from the ISO flow during the late period of typhoon development. This CKS-ISO difference is dominated by the -(〖u_s^’ v〗_s^’ (∂u_I^’)/∂y) ̅ term associated with the strengthened ISO cyclonic circulation (-(∂u_I^’)/∂y>0) and the greater momentum transport (〖u_s^’ v〗_s^’) of intense typhoons. Thus, as ISO and typhoons intensified, intense typhoons gain more energy from ISO. In addition, both the intense typhoons and their accompanying ISO cyclonic circulation are still located over the warm ocean due to their slower speed of movement. The moisture provided by the southwesterly flows at the southern flank of this ISO cyclonic circulation was also favorable for the latent heat release of intense typhoons and converted more typhoon available potential energy into typhoon kinetic energy. This positive feedback causes intense typhoons to receive more energy and further results in more intensification of intense typhoons. This research indicates that scale interaction plays an important role in the development of typhoon intensity.</p> <p> </p>
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Hsu, Tzu-Han, Wei-Ting Chen, Chien-Ming Wu, and Min-Ken Hsieh. "The Observation-Based Index to Investigate the Role of the Lee Vortex in Enhancing Air Pollution over Northwestern Taiwan." Journal of Applied Meteorology and Climatology, January 23, 2023. http://dx.doi.org/10.1175/jamc-d-22-0102.1.
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Abstract This study quantifies the potential effect of the lee vortex on the fine particulate matter (PM2.5) pollution deterioration under the complex topography in Taiwan using observational data. We select the lee-vortex days that favor the development of the lee vortices in northwestern Taiwan under the southeasterly synoptic winds. We then define the enhancement index that discerns the areas with the high occurrence frequencies of the PM2.5 enhancement under the flow regime relative to the seasonal background concentrations. Under the lee-vortex days, the center of western Taiwan exhibits enhancement indices higher than 0.65. In addition, during the consecutive lee-vortex days, the index characterizes a northward shift in the PM2.5 enhanced areas under the subtle transition of the background wind directions. The areas with indices higher than 0.65 expand on the 2nd day in northwestern Taiwan; the number of stations exhibiting indices higher than 0.8 increases by three folds from the 1st to the 2nd day. The idealized numerical simulations using the Taiwan vector vorticity equation cloud-resolving model (TaiwanVVM) explicitly resolve the structures of lee side circulations and the associated pollutant transport, and their evolutions are highly sensitive to the background winds.