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Christopher S. Velden - One of the best experts on this subject based on the ideXlab platform.
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strategies for assimilating high density Atmospheric Motion vectors into a regional tropical cyclone forecast model hwrf
Atmosphere, 2020Co-Authors: William E Lewis, Christopher S. Velden, David StettnerAbstract:In recent years, Atmospheric numerical modeling frameworks and satellite observing systems have both undergone significant advances. While these developments offer considerable potential for improving forecasts of high-impact weather events such as tropical cyclones (TC), much work remains to be done regarding the targeted processing and optimal use of observations now becoming available with high spatiotemporal resolution. Using the 2019 version of NCEP’s HWRF model, we explore several different strategies for the assimilation of TC-scale, high-density Atmospheric Motion vectors (AMVs) derived from the new-generation GOES-R series of geostationary satellites. Using 2017’s Atlantic Hurricane Irma as a case study, we examine the HWRF forecast impacts of observation pre-processing, including thinning and adjustments to observation errors. It is demonstrated that enhanced vortex-scale GOES-16 AMVs contribute to notable improvements in HWRF track forecast error compared to a baseline control experiment that does not incorporate the high-density AMVs. Impacts on TC intensity and structure (i.e., wind radii) forecast errors are less robust, but results from the optimization experiments suggest that further work (both with regard to data assimilation strategies and advancements in the methods themselves) should lead to improvements in these forecast variables as well.
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quantitative assessment of state dependent Atmospheric Motion vector uncertainties
Journal of Applied Meteorology and Climatology, 2019Co-Authors: Derek J Posselt, Kevin J. Mueller, Lei Huang, F W Irion, Shannon Brown, David Santek, Christopher S. VeldenAbstract:AbstractThis study examines the error characteristics of Atmospheric Motion vectors (AMVs) obtained by tracking the movement of water vapor features. A high-resolution numerical simulation of a dyn...
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demonstration with special tci 15 datasets of potential impacts of new generation satellite Atmospheric Motion vectors on navy regional and global models
Weather and Forecasting, 2018Co-Authors: Russell L Elsberry, Christopher S. Velden, Eric A Hendricks, Michael M Bell, Melinda Peng, Eleanor Casas, Qingyun ZhaoAbstract:AbstractA dynamic initialization assimilation scheme is demonstrated utilizing rapid-scan Atmospheric Motion vectors (AMVs) at 15-min intervals to simulate the real-time capability that now exists ...
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impact of enhanced Atmospheric Motion vectors on hwrf hurricane analyses and forecasts with different data assimilation configurations
Monthly Weather Review, 2018Co-Authors: Shixuan Zhang, Christopher S. VeldenAbstract:AbstractThe impacts of enhanced satellite-derived Atmospheric Motion vectors (AMVs) on the numerical prediction of intensity changes during Hurricanes Gonzalo (2014) and Joaquin (2015) are examined. Enhanced AMVs benefit from special data-processing strategies and are examined for impact on model forecasts via assimilation experiments by employing the National Centers for Environmental Prediction (NCEP) operational Hurricane Weather Research and Forecasting (HWRF) Model using a Gridpoint Statistical Interpolation analysis system (GSI)-based ensemble–variational hybrid system. Two different data assimilation (DA) configurations, one with and one without the use of vortex initialization (VI), are compared. It is found that the assimilation of enhanced AMVs can improve the HWRF track and intensity forecasts of Gonzalo and Joaquin during their intensity change phases. The degree of data impact depends on the DA configuration used. Overall, assimilation of enhanced AMVs in the innermost domain (e.g., storm inn...
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effect of enhanced satellite derived Atmospheric Motion vectors on numerical weather prediction in east asia using an adjoint based observation impact method
Weather and Forecasting, 2017Co-Authors: Myunghwan Kim, Christopher S. Velden, Hyun Mee Kim, Jinwoong Kim, Sungmin Kim, Brett T HooverAbstract:AbstractWhen producing forecasts by integrating a numerical weather prediction model from an analysis, not all observations assimilated into the analysis improve the forecast. Therefore, the impact of particular observations on the forecast needs to be evaluated quantitatively to provide relevant information about the impact of the observing system. One way to assess the observation impact is to use an adjoint-based method that estimates the impact of each assimilated observation on reducing the error of the forecast. In this study, the Weather Research and Forecasting Model and its adjoint are used to evaluate the impact of several types of observations, including enhanced satellite-derived Atmospheric Motion vectors (AMVs) that were made available during observation campaigns for two typhoons: Sinlaku and Jangmi, which both formed in the western North Pacific during September 2008. Without the assimilation of enhanced AMV data, radiosonde observations and satellite radiances show the highest total obser...
Graeme Kelly - One of the best experts on this subject based on the ideXlab platform.
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diagnosing Atmospheric Motion vector observation errors for an operational high resolution data assimilation system
Quarterly Journal of the Royal Meteorological Society, 2017Co-Authors: M Cordoba, Graeme Kelly, Sarah L Dance, Nancy Nichols, Joanne A WallerAbstract:Atmospheric Motion vectors (AMVs) are wind observations derived by tracking cloud or water-vapour features in consecutive satellite images. These observations are incorporated into numerical weather prediction (NWP) through data assimilation. In the assimilation algorithm, the weighting given to an observation is determined by the uncertainty associated with its measurement and representation. Previous studies assessing AMV uncertainty have used direct comparisons between AMVs with collocated radiosonde data and AMVs derived from Observing System Simulation Experiments (OSSEs). These have shown that AMV error is horizontally correlated with the characteristic length-scale up to 200 km. In this work, we take an alternative approach and estimate AMV error variance and horizontal error correlation using background and analysis residuals obtained from the Met Office limited-area, 3 km horizontal grid-length data assimilation system. The results show that the observation-error variance profile ranges from 5.2–14.1 s m2 s−2, with the highest values occurring at high and medium heights. This is indicative that the maximum error variance occurs where wind speed and shear, in combination, are largest. With the exception of AMVs derived from the High Resolution Visible channel, the results show horizontal observation-error correlations at all heights in the atmosphere, with correlation length-scales ranging between 140 and 200 km. These horizontal length-scales are significantly larger than current AMV observation-thinning distances used in the Met Office high-resolution assimilation.
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understanding Atmospheric Motion vector vertical representativity using a simulation study and first guess departure statistics
Journal of Applied Meteorology and Climatology, 2015Co-Authors: P Lean, Stefano Migliorini, Graeme KellyAbstract:AbstractAtmospheric Motion vectors (AMVs) have been produced for decades and remain an important source of wind information. Many studies have suggested that the traditional interpretation of AMVs as representative of the wind at cloud top is suboptimal and that they are more representative of the winds within the cloud. This paper investigates the vertical representativity of cloudy AMVs using both first-guess departure [observation − background (O − B)] statistics and the simulation-study technique. A state-of-the-art convection-permitting mesoscale model (“UKV”) is used in conjunction with a radiative transfer model and the Nowcasting Satellite Application Facility (NWCSAF) AMV package to produce synthetic AMVs over a 1-month period. The simulated upper-level AMVs suffered from large height-assignment errors uncharacteristic of those in reality; these issues were partially alleviated by using the model cloud top instead of the assigned height. In agreement with previous studies, both the simulated and ...
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OPERATIONAL USE OF Atmospheric Motion VECTORS AT ECMWF
2015Co-Authors: Claire Delsol, Jean-noël Thépaut, Niels Bormann, Graeme Kelly, Lueder Von Bremen, Peter BauerAbstract:A review of the status of Atmospheric Motion Vectors (AMVs), monitored and assimilated operationally at the European Centre for Medium Range Weather Forecasts (ECMWF), is presented. The period since the last workshop saw a number of satellite replacements. Currently, data from five different geostationary satellites are used in operations (from METEOSAT-9 and-7, GOES-11 and-12, and MTSAT-1R), together with polar AMVs from MODIS on Terra and Aqua. A number of additional AMV datasets are being monitored with a view of eventual operational assimilation, and we report on the results of the monitoring efforts so far. Winds have been derived by CIMSS from the infrared channel of the AVHRR instrument on the NOAA satellites. While the data are relatively sparse, assimilation trials in a system that uses a limited amount of satellite observations document a small positive forecast impact from the AVHRR winds. This also makes the data attractive for reanalyses. In addition, direct-broadcast MODIS winds are now available to improve the timeliness of this important dataset. A greater coverage is obtained for the early-cutoff NWP runs. AMVs from CMA’s FY-2C now include quality indicator information, prompting a re-assessment of the quality of these winds. Lastly, winds from the stereo-viewing MISR instrument on Terra have been compared to the ECMWF first guess, showing broadly similar first guess statistics to other AMVs from geostationary or polar satellites, despite a supposedly much better height assignment
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IMPACT OF Atmospheric Motion VECTORS ON GLOBAL NUMERICAL WEATHER PREDICTION
2015Co-Authors: Jean-noël Thépaut, Niels Bormann, Claire Delsol, Graeme KellyAbstract:The importance of satellite data at large is now such that they provide the main sources of information for numerical weather prediction (NWP) models. However, the role played by Atmospheric Motion Vectors (AMVs), evaluated via a series of Observing System Experiments (OSEs), remains essential in the Global Observing System (GOS). It is in particular shown that geostationary AMVs contribute to the reduction of humidity forecast error in the Tropics. Polar AMVs derived from tracking clouds and water vapour features with MODIS onboard AQUA and TERRA continue to contribute significantly to the reduction of forecast error, especially in the Southern Hemisphere for the period under investigation. It is finally shown that MODIS IR winds alone have a positive impact on the ECMWF forecasting system, giving some prospect and incentive to the Space Agencies for deriving polar AMVs from current and future imagers that will embark on the operational METOP (AVHRR) and NPOESS (VIIRS) satellites
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the spatial structure of observation errors in Atmospheric Motion vectors from geostationary satellite data
Monthly Weather Review, 2003Co-Authors: Niels Bormann, Graeme Kelly, Sami Saarinen, Jean-noël ThépautAbstract:Abstract This study investigates and quantifies in detail the spatial correlations of random errors in Atmospheric Motion vectors (AMVs) derived by tracking structures in imagery from geostationary satellites. A good specification of the observation error is essential to assimilate any kind of observation for numerical weather prediction in a near-optimal way. For AMVs, height assignment, tracking of similar cloud structures, or quality control procedures may introduce spatially correlated errors. The spatial structure of the error correlations is investigated based on a 1-yr dataset of pairs of collocations between AMVs and radiosonde observations. Assuming spatially uncorrelated sonde errors, the spatial AMV error correlations are obtained over dense sonde networks. Results for operational infrared and water vapor wind datasets from Meteosat-5 and -7, Geostationary Operational Environmental Satellite-8 and -10 (GOES-8 and -10), and Geostationary Meteorological Satellite-5 (GMS-5) are presented. Winds fr...
Niels Bormann - One of the best experts on this subject based on the ideXlab platform.
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OPERATIONAL USE OF Atmospheric Motion VECTORS AT ECMWF
2015Co-Authors: Claire Delsol, Jean-noël Thépaut, Niels Bormann, Graeme Kelly, Lueder Von Bremen, Peter BauerAbstract:A review of the status of Atmospheric Motion Vectors (AMVs), monitored and assimilated operationally at the European Centre for Medium Range Weather Forecasts (ECMWF), is presented. The period since the last workshop saw a number of satellite replacements. Currently, data from five different geostationary satellites are used in operations (from METEOSAT-9 and-7, GOES-11 and-12, and MTSAT-1R), together with polar AMVs from MODIS on Terra and Aqua. A number of additional AMV datasets are being monitored with a view of eventual operational assimilation, and we report on the results of the monitoring efforts so far. Winds have been derived by CIMSS from the infrared channel of the AVHRR instrument on the NOAA satellites. While the data are relatively sparse, assimilation trials in a system that uses a limited amount of satellite observations document a small positive forecast impact from the AVHRR winds. This also makes the data attractive for reanalyses. In addition, direct-broadcast MODIS winds are now available to improve the timeliness of this important dataset. A greater coverage is obtained for the early-cutoff NWP runs. AMVs from CMA’s FY-2C now include quality indicator information, prompting a re-assessment of the quality of these winds. Lastly, winds from the stereo-viewing MISR instrument on Terra have been compared to the ECMWF first guess, showing broadly similar first guess statistics to other AMVs from geostationary or polar satellites, despite a supposedly much better height assignment
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IMPACT OF Atmospheric Motion VECTORS ON GLOBAL NUMERICAL WEATHER PREDICTION
2015Co-Authors: Jean-noël Thépaut, Niels Bormann, Claire Delsol, Graeme KellyAbstract:The importance of satellite data at large is now such that they provide the main sources of information for numerical weather prediction (NWP) models. However, the role played by Atmospheric Motion Vectors (AMVs), evaluated via a series of Observing System Experiments (OSEs), remains essential in the Global Observing System (GOS). It is in particular shown that geostationary AMVs contribute to the reduction of humidity forecast error in the Tropics. Polar AMVs derived from tracking clouds and water vapour features with MODIS onboard AQUA and TERRA continue to contribute significantly to the reduction of forecast error, especially in the Southern Hemisphere for the period under investigation. It is finally shown that MODIS IR winds alone have a positive impact on the ECMWF forecasting system, giving some prospect and incentive to the Space Agencies for deriving polar AMVs from current and future imagers that will embark on the operational METOP (AVHRR) and NPOESS (VIIRS) satellites
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Atmospheric Motion vectors from model simulations part ii interpretation as spatial and vertical averages of wind and role of clouds
Journal of Applied Meteorology and Climatology, 2014Co-Authors: Angeles Hernandezcarrascal, Niels BormannAbstract:AbstractThis is the second part of a two-part paper whose main objective is to improve the characterization of Atmospheric Motion vectors (AMVs) and their errors to guide developments in the use of AMVs in numerical weather prediction (NWP). AMVs tend to exhibit considerable systematic and random errors. These errors can arise in the AMV derivation or the interpretation of AMVs as single-level point estimates of wind. An important difficulty in the study of AMV errors is the scarcity of collocated observations of clouds and wind. The study uses instead a simulation framework: geostationary imagery for Meteorological Satellite-8 (Meteosat-8) is generated from a high-resolution simulation with the Weather Research and Forecasting regional model, and AMVs are derived from sequences of these simulated images. The NWP model provides the “truth” with a sophisticated description of the atmosphere. This second part focuses on alternative interpretations of AMVs. The key results are 1) that interpreting the AMVs a...
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Atmospheric Motion vectors from model simulations part i methods and characterization as single level estimates of wind
Journal of Applied Meteorology and Climatology, 2014Co-Authors: Niels Bormann, Regis Borde, Angeles Hernandezcarrascal, Hansjoachim Lutz, Jason A Otkin, Steve WanzongAbstract:The objective of this study is to improve the characterization of satellite-derived Atmospheric Motion vectors (AMVs) and their errors to guide developments in the use of AMVs in numerical weather prediction. AMVs tend to exhibit considerable systematic and random errors that arise in the derivation or the interpretation of AMVs as single-level point observations of wind. One difficulty in the study of AMV errors is the scarcity of collocated observations of clouds and wind. This study uses instead a simulation framework: geostationary imagery for Meteosat-8 is generated from a high-resolution simulation with the Weather Research and Forecasting regional model, and AMVs are derived from sequences of these images. The forecast model provides the ‘‘truth’’ with a sophisticated description of the atmosphere. The study considers infrared and water vapor AMVs from cloudy scenes. This is the first part of a two-part paper, and it introduces the frameworkandprovides afirstevaluationintermsofthebrightnesstemperaturesofthesimulatedimagesand the derived AMVs. The simulated AMVs show a considerable global bias in the height assignment (60– 75hPa) that is not observed in real AMVs. After removal of this bias, however, the statistics comparing the simulated AMVs with the true model wind show characteristics that are similar to statistics comparing real AMVs with short-range forecasts (speed bias and root-mean-square vector difference typically agree to within 1ms 21 ). This result suggests that the error in the simulated AMVs is comparable to or larger than that in real AMVs. There is evidence for significant spatial, temporal, and vertical error correlations, with the scales for the spatial error correlations being consistent with estimates for real data.
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the spatial structure of observation errors in Atmospheric Motion vectors from geostationary satellite data
Monthly Weather Review, 2003Co-Authors: Niels Bormann, Graeme Kelly, Sami Saarinen, Jean-noël ThépautAbstract:Abstract This study investigates and quantifies in detail the spatial correlations of random errors in Atmospheric Motion vectors (AMVs) derived by tracking structures in imagery from geostationary satellites. A good specification of the observation error is essential to assimilate any kind of observation for numerical weather prediction in a near-optimal way. For AMVs, height assignment, tracking of similar cloud structures, or quality control procedures may introduce spatially correlated errors. The spatial structure of the error correlations is investigated based on a 1-yr dataset of pairs of collocations between AMVs and radiosonde observations. Assuming spatially uncorrelated sonde errors, the spatial AMV error correlations are obtained over dense sonde networks. Results for operational infrared and water vapor wind datasets from Meteosat-5 and -7, Geostationary Operational Environmental Satellite-8 and -10 (GOES-8 and -10), and Geostationary Meteorological Satellite-5 (GMS-5) are presented. Winds fr...
Thomas Dubos - One of the best experts on this subject based on the ideXlab platform.
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equations of Atmospheric Motion in non eulerian vertical coordinates vector invariant form and quasi hamiltonian formulation
Monthly Weather Review, 2014Co-Authors: Thomas Dubos, Marine TortAbstract:AbstractThe curl form of equations of inviscid Atmospheric Motion in general non-Eulerian coordinates is obtained. Narrowing down to a general vertical coordinate, a quasi-Hamiltonian form is then obtained in a Lagrangian, isentropic, mass-based or z-based vertical coordinate. In non-Lagrangian vertical coordinates, the conservation of energy by the vertical transport terms results from the invariance of energy under the vertical relabeling of fluid parcels. A complete or partial separation between the horizontal and vertical dynamics is achieved, except in the Eulerian case. The horizontal–vertical separation is especially helpful for (quasi-)hydrostatic systems characterized by vanishing vertical momentum. Indeed for such systems vertical momentum balance reduces to a simple statement: total energy is stationary with respect to adiabatic vertical displacements of fluid parcels. From this point of view the purpose of (quasi-)hydrostatic balance is to determine the vertical positions of fluid parcels, for...
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usual approximations to the equations of Atmospheric Motion a variational perspective
Journal of the Atmospheric Sciences, 2014Co-Authors: Marine Tort, Thomas DubosAbstract:AbstractThe usual geophysical approximations are reframed within a variational framework. Starting from the Lagrangian of the fully compressible Euler equations expressed in a general curvilinear coordinates system, Hamilton’s principle of least action yields Euler–Lagrange equations of Motion. Instead of directly making approximations in these equations, the approach followed is that of Hamilton’s principle asymptotics; that is, all approximations are performed in the Lagrangian. Using a coordinate system where the geopotential is the third coordinate, diverse approximations are considered. The assumptions and approximations covered are 1) particular shapes of the geopotential; 2) shallowness of the atmosphere, which allows for the approximation of the relative and planetary kinetic energy; 3) small vertical velocities, implying quasi-hydrostatic systems; and 4) pseudoincompressibility, enforced by introducing a Lagangian multiplier.This variational approach greatly facilitates the derivation of the equa...
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Usual Approximations to the Equations of Atmospheric Motion: A Variational Perspective
Journal of the Atmospheric Sciences, 2014Co-Authors: Marine Tort, Thomas DubosAbstract:The usual geophysical approximations are reframed within a variational framework. Starting from the Lagrangian of the fully compressible Euler equations expressed in a general curvilinear coordinates system, Hamilton's principle of least action yields Euler-Lagrange equations of Motion. Instead of directly making approximations in these equations, the approach followed is that of Hamilton's principle asymptotics; that is, all approximations are performed in the Lagrangian. Using a coordinate system where the geopotential is the third coordinate, diverse approximations are considered. The assumptions and approximations covered are 1) particular shapes of the geopotential; 2) shallowness of the atmosphere, which allows for the approximation of the relative and planetary kinetic energy; 3) small vertical velocities, implying quasi-hydrostatic systems; and 4) pseudoincompressibility, enforced by introducing a Lagangian multiplier. This variational approach greatly facilitates the derivation of the equations and systematically ensures their dynamical consistency. Indeed, the symmetry properties of the approximated Lagrangian imply the conservation of energy, potential vorticity, and momentum. Justification of the equations then relies, as usual, on a proper order-of-magnitude analysis. As an illustrative example, the asymptotic consistency of recently introduced shallow-atmosphere equations with a complete Coriolis force is discussed, suggesting additional corrections to the pressure gradient and gravity.
Marine Tort - One of the best experts on this subject based on the ideXlab platform.
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equations of Atmospheric Motion in non eulerian vertical coordinates vector invariant form and quasi hamiltonian formulation
Monthly Weather Review, 2014Co-Authors: Thomas Dubos, Marine TortAbstract:AbstractThe curl form of equations of inviscid Atmospheric Motion in general non-Eulerian coordinates is obtained. Narrowing down to a general vertical coordinate, a quasi-Hamiltonian form is then obtained in a Lagrangian, isentropic, mass-based or z-based vertical coordinate. In non-Lagrangian vertical coordinates, the conservation of energy by the vertical transport terms results from the invariance of energy under the vertical relabeling of fluid parcels. A complete or partial separation between the horizontal and vertical dynamics is achieved, except in the Eulerian case. The horizontal–vertical separation is especially helpful for (quasi-)hydrostatic systems characterized by vanishing vertical momentum. Indeed for such systems vertical momentum balance reduces to a simple statement: total energy is stationary with respect to adiabatic vertical displacements of fluid parcels. From this point of view the purpose of (quasi-)hydrostatic balance is to determine the vertical positions of fluid parcels, for...
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usual approximations to the equations of Atmospheric Motion a variational perspective
Journal of the Atmospheric Sciences, 2014Co-Authors: Marine Tort, Thomas DubosAbstract:AbstractThe usual geophysical approximations are reframed within a variational framework. Starting from the Lagrangian of the fully compressible Euler equations expressed in a general curvilinear coordinates system, Hamilton’s principle of least action yields Euler–Lagrange equations of Motion. Instead of directly making approximations in these equations, the approach followed is that of Hamilton’s principle asymptotics; that is, all approximations are performed in the Lagrangian. Using a coordinate system where the geopotential is the third coordinate, diverse approximations are considered. The assumptions and approximations covered are 1) particular shapes of the geopotential; 2) shallowness of the atmosphere, which allows for the approximation of the relative and planetary kinetic energy; 3) small vertical velocities, implying quasi-hydrostatic systems; and 4) pseudoincompressibility, enforced by introducing a Lagangian multiplier.This variational approach greatly facilitates the derivation of the equa...
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Usual Approximations to the Equations of Atmospheric Motion: A Variational Perspective
Journal of the Atmospheric Sciences, 2014Co-Authors: Marine Tort, Thomas DubosAbstract:The usual geophysical approximations are reframed within a variational framework. Starting from the Lagrangian of the fully compressible Euler equations expressed in a general curvilinear coordinates system, Hamilton's principle of least action yields Euler-Lagrange equations of Motion. Instead of directly making approximations in these equations, the approach followed is that of Hamilton's principle asymptotics; that is, all approximations are performed in the Lagrangian. Using a coordinate system where the geopotential is the third coordinate, diverse approximations are considered. The assumptions and approximations covered are 1) particular shapes of the geopotential; 2) shallowness of the atmosphere, which allows for the approximation of the relative and planetary kinetic energy; 3) small vertical velocities, implying quasi-hydrostatic systems; and 4) pseudoincompressibility, enforced by introducing a Lagangian multiplier. This variational approach greatly facilitates the derivation of the equations and systematically ensures their dynamical consistency. Indeed, the symmetry properties of the approximated Lagrangian imply the conservation of energy, potential vorticity, and momentum. Justification of the equations then relies, as usual, on a proper order-of-magnitude analysis. As an illustrative example, the asymptotic consistency of recently introduced shallow-atmosphere equations with a complete Coriolis force is discussed, suggesting additional corrections to the pressure gradient and gravity.