The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
P. Alexander Reinecke - One of the best experts on this subject based on the ideXlab platform.
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Instability in a class of explicit two‐time‐level semi‐Lagrangian schemes
Quarterly Journal of the Royal Meteorological Society, 2004Co-Authors: Dale R. Durran, P. Alexander ReineckeAbstract:Recently Gospodinov and collaborators derived a family of second-order two-time-level semi-Lagrangian schemes that contain an undetermined parameter α. It is shown that, when using one of these schemes to approximate the forcing terms in partial differential equations in a semi-Lagrangian Coordinate frame, the choice of α has a critical influence on the absolute stability of the method. Optimal stability properties are obtained by choosing α = ¼ which corresponds to the SETTLS scheme proposed by Hortal. Copyright © 2004 Royal Meteorological Society
Dale R. Durran - One of the best experts on this subject based on the ideXlab platform.
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Instability in a class of explicit two‐time‐level semi‐Lagrangian schemes
Quarterly Journal of the Royal Meteorological Society, 2004Co-Authors: Dale R. Durran, P. Alexander ReineckeAbstract:Recently Gospodinov and collaborators derived a family of second-order two-time-level semi-Lagrangian schemes that contain an undetermined parameter α. It is shown that, when using one of these schemes to approximate the forcing terms in partial differential equations in a semi-Lagrangian Coordinate frame, the choice of α has a critical influence on the absolute stability of the method. Optimal stability properties are obtained by choosing α = ¼ which corresponds to the SETTLS scheme proposed by Hortal. Copyright © 2004 Royal Meteorological Society
Christiane Jablonowski - One of the best experts on this subject based on the ideXlab platform.
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A Control-Volume Model of the Compressible Euler Equations with a Vertical Lagrangian Coordinate
Monthly Weather Review, 2013Co-Authors: Xi Chen, Natalia G. Andronova, Bram Van Leer, Joyce E. Penner, John P. Boyd, Christiane Jablonowski, Shian-jiann LinAbstract:AbstractAccurate and stable numerical discretization of the equations for the nonhydrostatic atmosphere is required, for example, to resolve interactions between clouds and aerosols in the atmosphere. Here the authors present a modification of the hydrostatic control-volume approach for solving the nonhydrostatic Euler equations with a Lagrangian vertical Coordinate. A scheme with low numerical diffusion is achieved by introducing a low Mach number approximate Riemann solver (LMARS) for atmospheric flows. LMARS is a flexible way to ensure stability for finite-volume numerical schemes in both Eulerian and vertical Lagrangian configurations. This new approach is validated on test cases using a 2D (x–z) configuration.
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assessing tracer transport algorithms and the impact of vertical resolution in a finite volume dynamical core
Monthly Weather Review, 2012Co-Authors: James Kent, Christiane Jablonowski, Jared P Whitehead, Richard B RoodAbstract:AbstractModeling the transport of trace gases is an essential part of any atmospheric model. The tracer transport scheme in the Community Atmosphere Model finite-volume dynamical core (CAM-FV), which is part of the National Center for Atmospheric Research’s (NCAR’s) Community Earth System Model (CESM1), is investigated using multidimensional idealized advection tests. CAM-FV’s tracer transport algorithm makes use of one-dimensional monotonic limiters. The Colella–Sekora limiter, which is applied to increase accuracy where the data are smooth, is implemented into the CAM-FV framework, and compared with the more traditional monotonic limiter of the piecewise parabolic method (the default limiter). For 2D flow, CAM-FV splits dimensions, allowing overshoots and undershoots, with the Colella–Sekora limiter producing larger overshoots than the default limiter.The impact of vertical resolution is also explored. A vertical Lagrangian Coordinate is used in CAM-FV, and is periodically remapped back to a fixed Euler...
Shian-jiann Lin - One of the best experts on this subject based on the ideXlab platform.
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A Control-Volume Model of the Compressible Euler Equations with a Vertical Lagrangian Coordinate
Monthly Weather Review, 2013Co-Authors: Xi Chen, Natalia G. Andronova, Bram Van Leer, Joyce E. Penner, John P. Boyd, Christiane Jablonowski, Shian-jiann LinAbstract:AbstractAccurate and stable numerical discretization of the equations for the nonhydrostatic atmosphere is required, for example, to resolve interactions between clouds and aerosols in the atmosphere. Here the authors present a modification of the hydrostatic control-volume approach for solving the nonhydrostatic Euler equations with a Lagrangian vertical Coordinate. A scheme with low numerical diffusion is achieved by introducing a low Mach number approximate Riemann solver (LMARS) for atmospheric flows. LMARS is a flexible way to ensure stability for finite-volume numerical schemes in both Eulerian and vertical Lagrangian configurations. This new approach is validated on test cases using a 2D (x–z) configuration.
Ulrich Schmidt - One of the best experts on this subject based on the ideXlab platform.
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a quasi Lagrangian Coordinate system based on high resolution tracer observations implementation for the antarctic polar vortex
Atmospheric Chemistry and Physics, 2008Co-Authors: E Ivanova, C M Volk, O Riediger, H Klein, N Sitnikov, A E Ulanovskii, V Yushkov, F Ravegnani, T Mobius, Ulrich SchmidtAbstract:In order to quantitatively analyse the chemical and dynamical evolution of the polar vortex it has proven extremely useful to work with Coordinate systems that follow the vortex flow. We propose here a two-dimensional quasi-Lagrangian Coordinate system { χ i , Δ χ i }, based on the mixing ratio of a long-lived stratospheric trace gas i , and its systematic use with i = N 2 O, in order to describe the structure of a well-developed Antarctic polar vortex. In the Coordinate system { χ i , Δ χ i } the mixing ratio χ i is the vertical Coordinate and Δ χ i = χ i (Θ)− χ i vort (Θ) is the meridional Coordinate ( χ i vort (Θ) being a vertical reference profile in the vortex core). The quasi-Lagrangian Coordinates { χ i , Δ χ i } persist for much longer time than standard isentropic Coordinates, potential temperature Θ and equivalent latitude φ e , do not require explicit reference to geographic space, and can be derived directly from high-resolution in situ measurements. They are therefore well-suited for studying the evolution of the Antarctic polar vortex throughout the polar winter with respect to the relevant chemical and microphysical processes. By using the introduced Coordinate system { χ N 2 O, Δ χ N 2 O } we analyze the well-developed Antarctic vortex investigated during the APE-GAIA (Airborne Polar Experiment – Geophysica Aircraft in Antarctica – 1999) campaign (Carli et al., 2000). A criterion, which uses the local in-situ measurements of χ i = χ i (Θ) and attributes the inner vortex edge to a rapid change ( δ -step) in the meridional profile of the mixing ratio χ i , is developed to determine the (Antarctic) inner vortex edge. In turn, we suggest that the outer vortex edge of a well-developed Antarctic vortex can be attributed to the position of a local minimum of the χ H 2 O gradient in the polar vortex area. For a well-developed Antarctic vortex, the Δ χ N 2 O -parametrization of tracer-tracer relationships allows to distinguish the tracer inter-relationships in the vortex core, vortex boundary region and surf zone and to examine their meridional variation throughout these regions. This is illustrated by analyzing the tracer-tracer relationships χ i : χ N 2 O obtained from the in-situ data of the APE-GAIA campaign for i = CFC-11, CFC-12, H-1211 and SF 6 . A number of solitary anomalous points in the CFC-11 : N 2 O correlation, observed in the Antarctic vortex core, are interpreted in terms of small-scale cross-isentropic dispersion.
