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Michael S. Fox-rabinovitz - One of the best experts on this subject based on the ideXlab platform.
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Final Progress Report submitted via the DOE Energy Link (E-Link) in June 2009 [Collaborative Research: Decadal-to-Centennial Climate & Climate Change Studies with Enhanced Variable and Uniform Resolution GCMs Using Advanced Numerical Techniques]
2009Co-Authors: Michael S. Fox-rabinovitz, Jean CoteAbstract:The joint U.S-Canadian project has been devoted to: (a) decadal climate studies using developed state-of-the-art GCMs (General Circulation Models) with enhanced variable and uniform resolution; (b) development and implementation of advanced numerical techniques; (c) research in parallel computing and associated numerical methods; (d) atmospheric chemistry experiments related to climate issues; (e) validation of regional climate modeling strategies for nested- and Stretched-Grid models. The variable-resolution Stretched-Grid (SG) GCMs produce accurate and cost-efficient regional climate simulations with mesoscale resolution. The advantage of the Stretched Grid approach is that it allows us to preserve the high quality of both global and regional circulations while providing consistent interactions between global and regional scales and phenomena. The major accomplishment for the project has been the successful international SGMIP-1 and SGMIP-2 (Stretched-Grid Model Intercomparison Project, phase-1 and phase-2) based on this research developments and activities. The SGMIP provides unique high-resolution regional and global multi-model ensembles beneficial for regional climate modeling and broader modeling community. The U.S SGMIP simulations have been produced using SciDAC ORNL supercomputers. The results of the successful SGMIP multi-model ensemble simulations of the U.S. climate are available at the SGMIP web site (http://essic.umd.edu/~foxrab/sgmip.html) and through the link to the WMO/WCRP/WGNE web site: http://collaboration.cmc.ec.gc.ca/science/wgne. Collaborations with other international participants M. Deque (Meteo-France) and J. McGregor (CSIRO, Australia) and their centers and groups have been beneficial for the strong joint effort, especially for the SGMIP activities. The WMO/WCRP/WGNE endorsed the SGMIP activities in 2004-2008. This project reflects a trend in the modeling and broader communities to move towards regional and sub-regional assessments and applications important for the U.S. and Canadian public, business and policy decision makers, as well as for international collaborations on regional, and especially climate related issues.
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Stretched-Grid Model Intercomparison Project: decadal regional climate simulations with enhanced variable and uniform-resolution GCMs
Meteorology and Atmospheric Physics, 2008Co-Authors: Michael S. Fox-rabinovitz, Michel Deque, Bernard Dugas, John L Mcgregor, Jean Cote, A. BelochitskiAbstract:Variable-resolution GCMs using a global Stretched-Grid (SG) with enhanced resolution over the region(s) of interest is an established approach to regional climate modeling providing an efficient means for regional down-scaling to mesoscales. This approach has been used since the early-mid 90s by the French, U.S., Canadian, Australian and other climate modeling groups along with, or as an alternative to, the current widely-used nested-Grid approach. Stretched-Grid GCMs are used for continuous climate simulations as usual GCMs, with the only difference that variable-resolution Grids are used instead of more traditional uniform Grids. The important advantages of variable-resolution Stretched-Grid GCMs are that they do not require any lateral boundary conditions/forcing and are free of the associated undesirable computational problems. As a result, Stretched-Grid GCMs provide self-consistent interactions between global and regional scales while a high quality of global circulation is preserved, as in uniform-Grid GCMs.
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decadal regional climate simulations with enhanced variable and uniform-resolution GCMs
2008Co-Authors: Michael S. Fox-rabinovitz, Michel Deque, Jean Cote, A. BelochitskiAbstract:Springer-Verlag 2008SummaryVariable-resolution GCMs using a global Stretched-Grid(SG) with enhanced resolution over the region(s) of interestis an established approach to regional climate modelingproviding an efficient means for regional down-scaling tomesoscales. This approach has been used since the early-mid 90s by the French, U.S., Canadian, Australian andother climate modeling groups along with, or as an alter-native to, the current widely-used nested-Grid approach.Stretched-Grid GCMs are used for continuous climate simu-lations as usual GCMs, with the only difference that vari-able-resolution Grids are used instead of more traditionaluniform Grids. The important advantages of variable-reso-lution Stretched-Grid GCMs are that they do not require anylateral boundary conditions=forcing and are free of the as-sociated undesirable computational problems. As a result,Stretched-Grid GCMs provide self-consistent interactionsbetween global and regional scales while a high qualityof global circulation is preserved, as in uniform-Grid GCMs.The international SGMIP-2 (Stretched-Grid Model Inter-comparison Project, phase-2) includes 25-year (1979–2003)climate simulations using enhanced variable and uniform-resolution GCMs developed at major centers=groups inAustralia, Canada, France, and the U.S. The SGMIP-2 re-gional (North American) and global products are availableas a link of the WMO=WCRP=WGNE web site: http:==collaboration.cmc.ec.gc.ca=science=wgne. The SGMIP-2multi-model regional ensembles compare well with reanaly-sis and observations, in terms of spatial and temporaldiagnostics. Regional biases are mostly limited to about half(or less) of typical observational or reanalysis errors while ahigh quality of global circulation is preserved. SGMIP-2 wasendorsed by the WMO=WCRP=WGNE at its annual meet-ings in 2004–2007.
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Variable resolution general circulation models: Stretched‐Grid model intercomparison project (SGMIP)
Journal of Geophysical Research, 2006Co-Authors: Michael S. Fox-rabinovitz, Michel Deque, Bernard Dugas, Jean Cote, John L McgregorAbstract:[1] Variable resolution general circulation models (GCMs) using a global Stretched Grid with enhanced uniform resolution over the region(s) of interest have proven to be an established approach to regional climate modeling providing an efficient regional downscaling to mesoscales. This approach has been used since the early to mid-1990s by climate modeling groups from France, the United States, Canada, and Australia, among others, along with or as an alternative to the current widely used nested-Grid approach. Stretched-Grid GCMs are used for continuous/autonomous climate simulations, as are usual GCMs, with the only difference being that variable resolution Grids are used instead of more traditional uniform Grids. The important advantages of variable resolution Stretched-Grid GCMs are that they do not require any lateral boundary conditions/forcing and are free of the associated undesirable computational problems; as a result, they provide self-consistent interactions between global and regional scales of motion and their associated phenomena as in uniform Grid GCMs. The international Stretched-Grid model intercomparison project, phase 1 (SGMIP-1), using variable resolution GCMs developed at major centers/groups in Australia, Canada, France, and the United States, was initiated in 2001 and successfully conducted in 2002–2005. The results of the 12-year (1987–1998) climate simulations for a major part of North America are available at the SGMIP Web site: http://essic.umd.edu/∼foxrab/sgmip.html. The SGMIP-1 multimodel ensemble results for the region compare well with reanalysis and observations in terms of spatial and temporal diagnostics. Regional biases for time-averaged model products are mostly limited to about half (or less) of typical reanalysis errors, i.e., within the uncertainties of the available reanalyses, while a high quality of global circulation is preserved. SGMIP products are available to national and international programs such as the World Meteorological Organization/World Climate Research Program/Working Group on Numerical Experimentation (WMO/WCRP/WGNE).
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A Multiyear Ensemble Simulation of the U.S. Climate with a Stretched-Grid GCM
Monthly Weather Review, 2005Co-Authors: Michael S. Fox-rabinovitz, Lawrence L. Takacs, Ernesto H. Berbery, Ravi C. GovindarajuAbstract:Abstract Multiyear (1987–97) limited ensemble integrations using a Stretched-Grid GCM, previously developed and experimented with by the authors, are employed for U.S. regional climate simulations. The ensemble members (six in total) are produced at two different regional resolutions: three members with 60-km and the other three members with 10-km regional resolution. The use of these two finer and coarser regional resolution ensemble members allows one to examine the impact of resolution on the overall quality of the simulated regional fields. For the multiyear ensemble simulations, an efficient regional downscaling to realistic mesoscales has been obtained. The ensemble means of the midtroposphere prognostic variables (height and meridional wind) show an overall good resemblance to the global reanalysis, especially for summer. Low-level features like the warm season Great Plains low-level jet are well represented in the simulations. During winter the 100-km simulations develop a southward wind east of t...
Michael S Foxrabinovitz - One of the best experts on this subject based on the ideXlab platform.
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variable resolution general circulation models Stretched Grid model intercomparison project sgmip
Journal of Geophysical Research, 2006Co-Authors: Michael S Foxrabinovitz, Michel Deque, Bernard Dugas, Jean Cote, John L McgregorAbstract:[1] Variable resolution general circulation models (GCMs) using a global Stretched Grid with enhanced uniform resolution over the region(s) of interest have proven to be an established approach to regional climate modeling providing an efficient regional downscaling to mesoscales. This approach has been used since the early to mid-1990s by climate modeling groups from France, the United States, Canada, and Australia, among others, along with or as an alternative to the current widely used nested-Grid approach. Stretched-Grid GCMs are used for continuous/autonomous climate simulations, as are usual GCMs, with the only difference being that variable resolution Grids are used instead of more traditional uniform Grids. The important advantages of variable resolution Stretched-Grid GCMs are that they do not require any lateral boundary conditions/forcing and are free of the associated undesirable computational problems; as a result, they provide self-consistent interactions between global and regional scales of motion and their associated phenomena as in uniform Grid GCMs. The international Stretched-Grid model intercomparison project, phase 1 (SGMIP-1), using variable resolution GCMs developed at major centers/groups in Australia, Canada, France, and the United States, was initiated in 2001 and successfully conducted in 2002–2005. The results of the 12-year (1987–1998) climate simulations for a major part of North America are available at the SGMIP Web site: http://essic.umd.edu/∼foxrab/sgmip.html. The SGMIP-1 multimodel ensemble results for the region compare well with reanalysis and observations in terms of spatial and temporal diagnostics. Regional biases for time-averaged model products are mostly limited to about half (or less) of typical reanalysis errors, i.e., within the uncertainties of the available reanalyses, while a high quality of global circulation is preserved. SGMIP products are available to national and international programs such as the World Meteorological Organization/World Climate Research Program/Working Group on Numerical Experimentation (WMO/WCRP/WGNE).
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global simulation of tropospheric ozone using the university of maryland chemical transport model umd ctm 2 regional transport and chemistry over the central united states using a Stretched Grid
Journal of Geophysical Research, 2004Co-Authors: Rokjin J. Park, Georgiy L. Stenchikov, Kenneth E. Pickering, Dale J. Allen, Michael S FoxrabinovitzAbstract:[1] We use the Stretched-Grid version of the three-dimensional global University of Maryland Chemical Transport Model (UMD-CTM) to examine the effects of mesoscale meteorological features such as fronts and deep convection on regional-scale chemistry and transport. The Stretched-Grid model simulation, with a Grid configuration featuring a mesoscale resolution region centered over the central United States, was conducted for June 1985, and evaluated through comparisons with a set of aircraft observations of trace gases. We also present results from a uniform-Grid UMD-CTM simulation with a more conventional 2° × 2.5° horizontal resolution for the same time period to examine how well the Stretched-Grid global model simulates mesoscale features. The changes in middle and upper tropospheric CO and O3 due to convection from the model simulations are in good agreement with the range of measurements. The Stretched-Grid model shows better agreement with measurements than the uniform-Grid model for the enhancement of trace gases in upper troposphere outflow due to deep convection and for the gradient of trace gas mixing ratios across a cold front. Peak convective enhancement of CO in the upper troposphere is larger in the Stretched-Grid model simulation than in the uniform-Grid simulation, indicating a better representation of locally focused deep convective transport of polluted boundary layer air in the former. This type of vertical transport feature must be handled accurately if a model is to be used for intercontinental transport calculations. However, we find that deep convection in both model simulations, although better simulated in the Stretched-Grid model, is too widespread and too frequent. We find that net ozone production in the polluted boundary layer is ∼15% less in the fine-Grid region (0.5° resolution) of the Stretched-Grid model than in the same region of the 2° × 2.5° model due to less artificial dilution of ozone precursors. The net ozone production in convective outflow plumes is also smaller in the Stretched-Grid model than in the uniform-Grid model. We estimate the net flux of ozone from North America in the lowest 7 km to be 10 Gmol d−1 for the month of June using the results from the Stretched-Grid simulation. This value includes direct horizontal boundary layer flux, ozone that has been vertically transported from the boundary layer to free troposphere, and ozone that had been produced photochemically in the free troposphere.
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a variable resolution Stretched Grid general circulation model and data assimilation system with multiple areas of interest studying the anomalous regional climate events of 1998
Journal of Geophysical Research, 2002Co-Authors: Michael S Foxrabinovitz, Lawrence L. Takacs, Ravi C. GovindarajuAbstract:[1] The new Stretched-Grid (SG) design with multiple (four) areas of interest, one at each global quadrant, is implemented into both a SG general circulation model (GCM) and a SG data assimilation system (DAS). The four areas of interest include the United States/northern Mexico, the El Nino area/central South America, India/China, and the eastern Indian Ocean/Australia. Both SG-GCM and SG-DAS annual (November 1997 to December 1998) integrations are performed with 50-km regional resolution. The efficient regional downscaling to mesoscales is obtained for each of the four areas of interest, while the consistent interactions between regional and global scales and the high quality of global circulation are preserved. This is the advantage of the SG approach. The global variable-resolution DAS incorporating the SG-GCM has been developed and tested as an efficient tool for producing regional analyses and diagnostics with enhanced mesoscale resolution. The anomalous regional climate events of 1998 that occurred over the United States, Mexico, South America, China, India, African Sahel, and Australia are investigated in both simulation and data assimilation modes. The assimilated products are also used, along with gauge precipitation data, for validating the simulation results. The obtained results show that the SG-GCM and SG-DAS are capable of producing realistic high-quality simulated and assimilated products at mesoscale resolution for regional climate studies and applications.
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simulation of anomalous regional climate events with a variable resolution Stretched Grid gcm
Journal of Geophysical Research, 2000Co-Authors: Michael S FoxrabinovitzAbstract:The Stretched-Grid approach provides an efficient downscaling and consistent interactions between global and regional scales due to using one variable-resolution model for integrations. It is a workable alternative to the widely used nested-Grid approach introduced over a decade ago as a pioneering step in regional climate modeling. A variable-resolution finite-difference GCM (general circulation model) employing a Stretched Grid, with enhanced resolution over the United States as the area of interest, is used for simulating two anomalous regional climate events, the U.S. summer drought of 1988 and the U.S. summer flood of 1993. The special mode of integration using a Stretched-Grid GCM and data assimilation system is developed which allows for imitating the nested-Grid framework within a Stretched-Grid approach. The mode is useful for intercomparison purposes and for underlining the differences between these two approaches. The 1988 and 1993 integrations are performed for the 2 month period starting from mid-May. Regional resolutions used in most of the experiments is 60 km. The major goal and the result of the study is obtaining the efficient downscaling over the area of interest. The monthly mean prognostic regional fields for the Stretched-Grid integrations are remarkably close to those of the verifying analyses. Simulated precipitation patterns are successfully verified against gauge precipitation observations. The impact of finer 40 km regional resolution is investigated for the 1993 integration and an example of recovering subregional precipitation is presented. The obtained results show that the global variable-resolution Stretched-Grid approach is a viable candidate for regional and subregional climate studies and applications.
Rokjin J. Park - One of the best experts on this subject based on the ideXlab platform.
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global simulation of tropospheric ozone using the university of maryland chemical transport model umd ctm 2 regional transport and chemistry over the central united states using a Stretched Grid
Journal of Geophysical Research, 2004Co-Authors: Rokjin J. Park, Georgiy L. Stenchikov, Kenneth E. Pickering, Dale J. Allen, Michael S FoxrabinovitzAbstract:[1] We use the Stretched-Grid version of the three-dimensional global University of Maryland Chemical Transport Model (UMD-CTM) to examine the effects of mesoscale meteorological features such as fronts and deep convection on regional-scale chemistry and transport. The Stretched-Grid model simulation, with a Grid configuration featuring a mesoscale resolution region centered over the central United States, was conducted for June 1985, and evaluated through comparisons with a set of aircraft observations of trace gases. We also present results from a uniform-Grid UMD-CTM simulation with a more conventional 2° × 2.5° horizontal resolution for the same time period to examine how well the Stretched-Grid global model simulates mesoscale features. The changes in middle and upper tropospheric CO and O3 due to convection from the model simulations are in good agreement with the range of measurements. The Stretched-Grid model shows better agreement with measurements than the uniform-Grid model for the enhancement of trace gases in upper troposphere outflow due to deep convection and for the gradient of trace gas mixing ratios across a cold front. Peak convective enhancement of CO in the upper troposphere is larger in the Stretched-Grid model simulation than in the uniform-Grid simulation, indicating a better representation of locally focused deep convective transport of polluted boundary layer air in the former. This type of vertical transport feature must be handled accurately if a model is to be used for intercontinental transport calculations. However, we find that deep convection in both model simulations, although better simulated in the Stretched-Grid model, is too widespread and too frequent. We find that net ozone production in the polluted boundary layer is ∼15% less in the fine-Grid region (0.5° resolution) of the Stretched-Grid model than in the same region of the 2° × 2.5° model due to less artificial dilution of ozone precursors. The net ozone production in convective outflow plumes is also smaller in the Stretched-Grid model than in the uniform-Grid model. We estimate the net flux of ozone from North America in the lowest 7 km to be 10 Gmol d−1 for the month of June using the results from the Stretched-Grid simulation. This value includes direct horizontal boundary layer flux, ozone that has been vertically transported from the boundary layer to free troposphere, and ozone that had been produced photochemically in the free troposphere.
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Global simulation of tropospheric ozone using the University of Maryland Chemical Transport Model (UMD‐CTM): 2. Regional transport and chemistry over the central United States using a Stretched Grid
Journal of Geophysical Research, 2004Co-Authors: Rokjin J. Park, Georgiy L. Stenchikov, Kenneth E. Pickering, Dale J. Allen, Michael S. Fox-rabinovitzAbstract:[1] We use the Stretched-Grid version of the three-dimensional global University of Maryland Chemical Transport Model (UMD-CTM) to examine the effects of mesoscale meteorological features such as fronts and deep convection on regional-scale chemistry and transport. The Stretched-Grid model simulation, with a Grid configuration featuring a mesoscale resolution region centered over the central United States, was conducted for June 1985, and evaluated through comparisons with a set of aircraft observations of trace gases. We also present results from a uniform-Grid UMD-CTM simulation with a more conventional 2° × 2.5° horizontal resolution for the same time period to examine how well the Stretched-Grid global model simulates mesoscale features. The changes in middle and upper tropospheric CO and O3 due to convection from the model simulations are in good agreement with the range of measurements. The Stretched-Grid model shows better agreement with measurements than the uniform-Grid model for the enhancement of trace gases in upper troposphere outflow due to deep convection and for the gradient of trace gas mixing ratios across a cold front. Peak convective enhancement of CO in the upper troposphere is larger in the Stretched-Grid model simulation than in the uniform-Grid simulation, indicating a better representation of locally focused deep convective transport of polluted boundary layer air in the former. This type of vertical transport feature must be handled accurately if a model is to be used for intercontinental transport calculations. However, we find that deep convection in both model simulations, although better simulated in the Stretched-Grid model, is too widespread and too frequent. We find that net ozone production in the polluted boundary layer is ∼15% less in the fine-Grid region (0.5° resolution) of the Stretched-Grid model than in the same region of the 2° × 2.5° model due to less artificial dilution of ozone precursors. The net ozone production in convective outflow plumes is also smaller in the Stretched-Grid model than in the uniform-Grid model. We estimate the net flux of ozone from North America in the lowest 7 km to be 10 Gmol d−1 for the month of June using the results from the Stretched-Grid simulation. This value includes direct horizontal boundary layer flux, ozone that has been vertically transported from the boundary layer to free troposphere, and ozone that had been produced photochemically in the free troposphere.
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Global simulation of tropospheric ozone using the University of Maryland Chemical Transport Model (UMD-CTM): 1. Model description and evaluation
Journal of Geophysical Research, 2004Co-Authors: Rokjin J. Park, Georgiy L. Stenchikov, Kenneth E. Pickering, Dale J. Allen, Michael S. Fox-rabinovitzAbstract:[1] We have developed the three-dimensional global University of Maryland Chemical Transport Model (UMD-CTM), which can operate on a uniform horizontal Grid or operate with a Stretched-Grid feature that allows transport and chemistry to be computed with mesoscale resolution in a region of interest. The model is suitable for computing photochemical air quality over a specific region, as well as addressing interregional and intercontinental transport issues. The model contains options for a uniform Grid or a Stretched-Grid advection scheme and contains a fast chemical solver and schemes for convective transport, eddy diffusion, emissions, dry deposition, wet scavenging, and stratospheric influx. The model was run on a uniform Grid for a full year, and results were evaluated with a variety of surface, airborne, balloon-borne, and satellite observations from many regions of the world. The evaluation was quantified by means of an evaluation index, which compares the model versus observation differences with the variance in the measurements. For most species no systematic biases were found in the results. Results of a simulation with the Stretched-Grid version of the model are reported in part 2 of this series of papers [Park et al., 2004].
Georgiy L. Stenchikov - One of the best experts on this subject based on the ideXlab platform.
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A Three-Dimensional Total Odd Nitrogen (No(y)) Simulation During Sonex Using a Stretched-Grid Chemical Transport Model
2013Co-Authors: Dale J. Allen, Georgiy L. Stenchikov, Kenneth E. Pickering, Anne M. Thompson, Yutaka KondoAbstract:The relative importance of various odd nitrogen (NOy) sources including lightning, aircraft, and surface emissions on upper tropospheric total odd nitrogen is illustrated as a first application of the three-dimensional Stretched-Grid University of Maryland/Goddard Chemical-Transport Model (SG-GCTM). The SG-GCTM has been developed to look at the effect of localized sources and/or small-scale mixing processes on the large-scale or global chemical balance. For this simulation the Stretched Grid was chosen so that its maximum resolution is located over eastern North America and the North Atlantic; a region that includes most of the Subsonic Assessment (SASS) Ozone and Nitrogen Oxide Experiment (SONEX) flight paths. The SONEX period (October- November 1997) is simulated by driving the SG-GCTM with assimilated data from the Goddard Earth Observing System-Stratospheric Tracers of Atmospheric Transport Data Assimilation System (GEOS-STRAT DAS). A new algorithm is used to estimate the lightning flash rates needed to calculate NOy emission by lightning. This algorithm parameterizes the flash rate in terms of upper tropospheric convective mass flux. Model- calculated upper tropospheric NOy and NOy measurements from the NASA DC-8 aircraft are compared. Spatial variations in NOy were well captured especially with the Stretched- Grid run; however, model-calculated peaks due to "stratospheric" NOy are occasionally too large. The lightning algorithm reproduces the temporally and spatially averaged total flash rate accurately; however, the use of emissions from observed lightning flashes significantly improves the simulation on a few days, especially November 3, 1997, showing that significant uncertainty remains in parameterizing lightning in chemistry and transport models. Aircraft emissions contributed ;15% of the upper tropospheric NOy averaged along SONEX flight paths within the North Atlantic Flight Corridor with the contribution exceeding 40% during portions of some flights.
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global simulation of tropospheric ozone using the university of maryland chemical transport model umd ctm 2 regional transport and chemistry over the central united states using a Stretched Grid
Journal of Geophysical Research, 2004Co-Authors: Rokjin J. Park, Georgiy L. Stenchikov, Kenneth E. Pickering, Dale J. Allen, Michael S FoxrabinovitzAbstract:[1] We use the Stretched-Grid version of the three-dimensional global University of Maryland Chemical Transport Model (UMD-CTM) to examine the effects of mesoscale meteorological features such as fronts and deep convection on regional-scale chemistry and transport. The Stretched-Grid model simulation, with a Grid configuration featuring a mesoscale resolution region centered over the central United States, was conducted for June 1985, and evaluated through comparisons with a set of aircraft observations of trace gases. We also present results from a uniform-Grid UMD-CTM simulation with a more conventional 2° × 2.5° horizontal resolution for the same time period to examine how well the Stretched-Grid global model simulates mesoscale features. The changes in middle and upper tropospheric CO and O3 due to convection from the model simulations are in good agreement with the range of measurements. The Stretched-Grid model shows better agreement with measurements than the uniform-Grid model for the enhancement of trace gases in upper troposphere outflow due to deep convection and for the gradient of trace gas mixing ratios across a cold front. Peak convective enhancement of CO in the upper troposphere is larger in the Stretched-Grid model simulation than in the uniform-Grid simulation, indicating a better representation of locally focused deep convective transport of polluted boundary layer air in the former. This type of vertical transport feature must be handled accurately if a model is to be used for intercontinental transport calculations. However, we find that deep convection in both model simulations, although better simulated in the Stretched-Grid model, is too widespread and too frequent. We find that net ozone production in the polluted boundary layer is ∼15% less in the fine-Grid region (0.5° resolution) of the Stretched-Grid model than in the same region of the 2° × 2.5° model due to less artificial dilution of ozone precursors. The net ozone production in convective outflow plumes is also smaller in the Stretched-Grid model than in the uniform-Grid model. We estimate the net flux of ozone from North America in the lowest 7 km to be 10 Gmol d−1 for the month of June using the results from the Stretched-Grid simulation. This value includes direct horizontal boundary layer flux, ozone that has been vertically transported from the boundary layer to free troposphere, and ozone that had been produced photochemically in the free troposphere.
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Global simulation of tropospheric ozone using the University of Maryland Chemical Transport Model (UMD‐CTM): 2. Regional transport and chemistry over the central United States using a Stretched Grid
Journal of Geophysical Research, 2004Co-Authors: Rokjin J. Park, Georgiy L. Stenchikov, Kenneth E. Pickering, Dale J. Allen, Michael S. Fox-rabinovitzAbstract:[1] We use the Stretched-Grid version of the three-dimensional global University of Maryland Chemical Transport Model (UMD-CTM) to examine the effects of mesoscale meteorological features such as fronts and deep convection on regional-scale chemistry and transport. The Stretched-Grid model simulation, with a Grid configuration featuring a mesoscale resolution region centered over the central United States, was conducted for June 1985, and evaluated through comparisons with a set of aircraft observations of trace gases. We also present results from a uniform-Grid UMD-CTM simulation with a more conventional 2° × 2.5° horizontal resolution for the same time period to examine how well the Stretched-Grid global model simulates mesoscale features. The changes in middle and upper tropospheric CO and O3 due to convection from the model simulations are in good agreement with the range of measurements. The Stretched-Grid model shows better agreement with measurements than the uniform-Grid model for the enhancement of trace gases in upper troposphere outflow due to deep convection and for the gradient of trace gas mixing ratios across a cold front. Peak convective enhancement of CO in the upper troposphere is larger in the Stretched-Grid model simulation than in the uniform-Grid simulation, indicating a better representation of locally focused deep convective transport of polluted boundary layer air in the former. This type of vertical transport feature must be handled accurately if a model is to be used for intercontinental transport calculations. However, we find that deep convection in both model simulations, although better simulated in the Stretched-Grid model, is too widespread and too frequent. We find that net ozone production in the polluted boundary layer is ∼15% less in the fine-Grid region (0.5° resolution) of the Stretched-Grid model than in the same region of the 2° × 2.5° model due to less artificial dilution of ozone precursors. The net ozone production in convective outflow plumes is also smaller in the Stretched-Grid model than in the uniform-Grid model. We estimate the net flux of ozone from North America in the lowest 7 km to be 10 Gmol d−1 for the month of June using the results from the Stretched-Grid simulation. This value includes direct horizontal boundary layer flux, ozone that has been vertically transported from the boundary layer to free troposphere, and ozone that had been produced photochemically in the free troposphere.
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Global simulation of tropospheric ozone using the University of Maryland Chemical Transport Model (UMD-CTM): 1. Model description and evaluation
Journal of Geophysical Research, 2004Co-Authors: Rokjin J. Park, Georgiy L. Stenchikov, Kenneth E. Pickering, Dale J. Allen, Michael S. Fox-rabinovitzAbstract:[1] We have developed the three-dimensional global University of Maryland Chemical Transport Model (UMD-CTM), which can operate on a uniform horizontal Grid or operate with a Stretched-Grid feature that allows transport and chemistry to be computed with mesoscale resolution in a region of interest. The model is suitable for computing photochemical air quality over a specific region, as well as addressing interregional and intercontinental transport issues. The model contains options for a uniform Grid or a Stretched-Grid advection scheme and contains a fast chemical solver and schemes for convective transport, eddy diffusion, emissions, dry deposition, wet scavenging, and stratospheric influx. The model was run on a uniform Grid for a full year, and results were evaluated with a variety of surface, airborne, balloon-borne, and satellite observations from many regions of the world. The evaluation was quantified by means of an evaluation index, which compares the model versus observation differences with the variance in the measurements. For most species no systematic biases were found in the results. Results of a simulation with the Stretched-Grid version of the model are reported in part 2 of this series of papers [Park et al., 2004].
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A Uniform- and Variable-Resolution Stretched-Grid GCM Dynamical Core with Realistic Orography
Monthly Weather Review, 2000Co-Authors: Michael S. Fox-rabinovitz, Lawrence L. Takacs, Max J. Suarez, Georgiy L. Stenchikov, Ravi C. GovindarajuAbstract:The impact of introducing a realistic orographic forcing into a uniform- and variable-resolution Stretched-Grid GCM dynamical core is investigated by performing long-term and medium-range integrations. Comparisons are made between various Stretched-Grid simulations and a control that consists of a uniform Grid integration at high resolution. These comparisons include those where the orography has and has not been filtered to eliminate small-scale noise. Results from the region of interest with highest resolution show that 1) the Stretched-Grid GCM provides an efficient downscaling over the area of interest, that is, it properly simulates not only largescale but also mesoscale features; and 2) the introduction of orography has a greater impact than the effect of stretching. Results presented here suggest that dynamical core integrations with both uniform and Stretched Grids should consider orographic forcing as an integral part of the model dynamics.
Gerhard Krinner - One of the best experts on this subject based on the ideXlab platform.
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Effect of prescribed sea surface conditions on the modern and future Antarctic surface climate simulated by the ARPEGE atmosphere general circulation model
The Cryosphere, 2019Co-Authors: Julien Beaumet, Gerhard Krinner, Michel Deque, Cecile Agosta, Antoinette AliasAbstract:Owing to increase in snowfall, the Antarctic Ice Sheet surface mass balance is expected to increase by the end of the current century. Assuming no associated response of ice dynamics, this will be a negative contribution to sea-level rise. However, the assessment of these changes using dynam-ical downscaling of coupled climate model projections still bears considerable uncertainties due to poorly represented high-southern-latitude atmospheric circulation and sea surface conditions (SSCs), that is sea surface temperature and sea ice concentration. This study evaluates the Antarctic surface climate simulated using a global high-resolution atmospheric model and assesses the effects on the simulated Antarctic surface climate of two different SSC data sets obtained from two coupled climate model projections. The two coupled models from which SSCs are taken, MIROC-ESM and NorESM1-M, simulate future Antarctic sea ice trends at the opposite ends of the CMIP5 RCP8.5 projection range. The atmospheric model ARPEGE is used with a Stretched Grid configuration in order to achieve an average horizontal resolution of 35 km over Antarctica. Over the 1981-2010 period, ARPEGE is driven by the SSCs from MIROC-ESM, NorESM1-M and CMIP5 historical runs and by observed SSCs. These three simulations are evaluated against the ERA-Interim reanaly-ses for atmospheric general circulation as well as the MAR regional climate model and in situ observations for surface climate. For the late 21st century, SSCs from the same coupled climate models forced by the RCP8.5 emission scenario are used both directly and bias-corrected with an anomaly method which consists in adding the future climate anomaly from coupled model projections to the observed SSCs with taking into account the quantile distribution of these anomalies. We evaluate the effects of driving the atmospheric model by the bias-corrected instead of the original SSCs.
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oceanic forcing of antarctic climate change a study using a Stretched Grid atmospheric general circulation model
Journal of Climate, 2014Co-Authors: Gerhard Krinner, Martin Ménégoz, Chloe Largeron, Cecile Agosta, Claire BrutelvuilmetAbstract:AbstractA variable-resolution atmospheric general circulation model (AGCM) is used for climate change projections over the Antarctic. The present-day simulation uses prescribed observed sea surface conditions, while a set of five simulations for the end of the twenty-first century (2070–99) under the Special Report on Emissions Scenarios (SRES) A1B scenario uses sea surface condition anomalies from selected coupled ocean–atmosphere climate models from phase 3 of the Coupled Model Intercomparison Project (CMIP3). Analysis of the results shows that the prescribed sea surface condition anomalies have a very strong influence on the simulated climate change on the Antarctic continent, largely dominating the direct effect of the prescribed greenhouse gas concentration changes in the AGCM simulations. Complementary simulations with idealized forcings confirm these results. An analysis of circulation changes using self-organizing maps shows that the simulated climate change on regional scales is not principally c...
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snow cover sensitivity to black carbon deposition in the himalayas from atmospheric and ice core measurements to regional climate simulations
Atmospheric Chemistry and Physics, 2014Co-Authors: Martin Ménégoz, Anne Cozic, Patrick Ginot, Yves Balkanski, Gerhard Krinner, Olivier Boucher, S Lim, Paolo Laj, Hubert GalléeAbstract:Abstract. We applied a climate-chemistry global model to evaluate the impact of black carbon (BC) deposition on the Himalayan snow cover from 1998 to 2008. Using a Stretched Grid with a resolution of 50 km over this complex topography, the model reproduces reasonably well the remotely sensed observations of the snow cover duration. Similar to observations, modelled atmospheric BC concentrations in the central Himalayas reach a minimum during the monsoon and a maximum during the post- and pre-monsoon periods. Comparing the simulated BC concentrations in the snow with observations is more challenging because of their high spatial variability and complex vertical distribution. We simulated spring BC concentrations in surface snow varying from tens to hundreds of μg kg−1, higher by one to two orders of magnitude than those observed in ice cores extracted from central Himalayan glaciers at high elevations (>6000 m a.s.l.), but typical for seasonal snow cover sampled in middle elevation regions (
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snow cover sensitivity to black carbon deposition in the himalayas from atmospheric and ice core measurements to regional climate simulations
Atmospheric Chemistry and Physics, 2013Co-Authors: Martin Ménégoz, Anne Cozic, Patrick Ginot, Patrick Wagnon, Yves Balkanski, Hubert Gallée, Gerhard Krinner, Olivier BoucherAbstract:Abstract. We applied a climate-chemistry global model to evaluate the impact of black carbon (BC) deposition on the Himalayan snow cover from 1998 to 2008. Using a Stretched Grid with a resolution of 50 km over this complex topography, the model reproduces reasonably well the remotely sensed observations of the snow cover duration. Similar to observations, modelled atmospheric BC concentrations in the central Himalayas reach a minimum during the monsoon and a maximum during the post- and pre-monsoon periods. Comparing the simulated BC concentrations in the snow with observations is more challenging because of their high spatial variability and complex vertical distribution. We simulated spring BC concentrations in surface snow varying from tens to hundreds of μg kg −1 , higher by one to two orders of magnitude than those observed in ice cores extracted from central Himalayan glaciers at high elevations (>6000 m a.s.l.), but typical for seasonal snow cover sampled in middle elevation regions ( −2 leading to a localised warming between 0.05 and 0.3 °C.
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A 40-year accumulation dataset for Adelie Land, Antarctica and its application for model validation
Climate Dynamics, 2012Co-Authors: Cecile Agosta, Hubert Gallée, Gerhard Krinner, Christophe Genthon, Vincent Favier, Jan T. M. Lenaerts, Michiel R. Van Den BroekeAbstract:The GLACIOCLIM-SAMBA (GS) Antarctic accumulation monitoring network, which extends from the coast of Adelie Land to the Antarctic plateau, has been surveyed annually since 2004. The network includes a 156-km stake-line from the coast inland, along which accumulation shows high spatial and interannual variability with a mean value of 362 mm water equivalent a^−1. In this paper, this accumulation is compared with older accumulation reports from between 1971 and 1991. The mean and annual standard deviation and the km-scale spatial pattern of accumulation were seen to be very similar in the older and more recent data. The data did not reveal any significant accumulation trend over the last 40 years. The ECMWF analysis-based forecasts (ERA-40 and ERA-Interim), a Stretched-Grid global general circulation model (LMDZ4) and three regional circulation models (PMM5, MAR and RACMO2), all with high resolution over Antarctica (27–125 km), were tested against the GS reports. They qualitatively reproduced the meso-scale spatial pattern of the annual-mean accumulation except MAR. MAR significantly underestimated mean accumulation, while LMDZ4 and RACMO2 overestimated it. ERA-40 and the regional models that use ERA-40 as lateral boundary condition qualitatively reproduced the chronology of interannual variability but underestimated the magnitude of interannual variations. Two widely used climatologies for Antarctic accumulation agreed well with the mean GS data. The model-based climatology was also able to reproduce the observed spatial pattern. These data thus provide new stringent constraints on models and other large-scale evaluations of the Antarctic accumulation.
