A Non-hydrostatic Variable Resolution Atmospheric Model in ACME

2018 ◽  
Author(s):  
David Matthew Hall ◽  
Mark Taylor ◽  
Paul Ullrich ◽  
Carol Woodward
Keyword(s):  
Atmospheric Model ◽  
Variable Resolution

scholarly journals Vorticity-Divergence semi-Lagrangian Global Atmospheric Model SL-AV20: Dynamical Core

2016 ◽  
Author(s):  
Mikhail Tolstykh ◽  
Vladimir Shashkin ◽  
Rostislav Fadeev ◽  
Gordey Goyman
Keyword(s):  
Numerical Solutions ◽  
Climate Modeling ◽  
Region Of Interest ◽  
Weather Forecast ◽  
Seasonal Prediction ◽  
Atmospheric Model ◽  
Medium Range Weather Forecast ◽  
Variable Resolution ◽  
Dynamical Core ◽  
Global Atmospheric Model

Abstract. SL-AV (Semi-Lagranginan Absolute Vorticity) is a global atmospheric model. Its latest version SL-AV20 provides global operational medium-range weather forecast with 20 km resolution over Russia. The lower resolution configurations of SL-AV20 are being tested for seasonal prediction and climate modeling. The article presents the model dynamical core. Its main features are vorticity-divergence formulation at the unstaggered grid, high-order finite-difference approximations, semi-Lagrangian semi-implicit discretization and the reduced latitude-longitude grid with variable resolution in latitude. The accuracy of SL-AV20 numerical solutions using reduced lat-lon grid and the variable resolution in latitude is tested with two idealized testcases. The results agree well with other published model solutions. It is shown that the use of the reduced grid having up to 25 % less grid points than the regular grid does not significantly affect the accuracy. Variable resolution in latitude allows to improve the accuracy of solution in the region of interest.

scholarly journals Vorticity-divergence semi-Lagrangian global atmospheric model SL-AV20: dynamical core

2017 ◽  
Vol 10 (5) ◽  
pp. 1961-1983 ◽  
Author(s):  
Mikhail Tolstykh ◽  
Vladimir Shashkin ◽  
Rostislav Fadeev ◽  
Gordey Goyman
Keyword(s):  
Numerical Solutions ◽  
Climate Modeling ◽  
Region Of Interest ◽  
Weather Forecast ◽  
Seasonal Prediction ◽  
Atmospheric Model ◽  
Test Case ◽  
Medium Range Weather Forecast ◽  
Variable Resolution ◽  
Dynamical Core

Abstract. SL-AV (semi-Lagrangian, based on the absolute vorticity equation) is a global hydrostatic atmospheric model. Its latest version, SL-AV20, provides global operational medium-range weather forecast with 20 km resolution over Russia. The lower-resolution configurations of SL-AV20 are being tested for seasonal prediction and climate modeling. The article presents the model dynamical core. Its main features are a vorticity-divergence formulation at the unstaggered grid, high-order finite-difference approximations, semi-Lagrangian semi-implicit discretization and the reduced latitude–longitude grid with variable resolution in latitude. The accuracy of SL-AV20 numerical solutions using a reduced lat–lon grid and the variable resolution in latitude is tested with two idealized test cases. Accuracy and stability of SL-AV20 in the presence of the orography forcing are tested using the mountain-induced Rossby wave test case. The results of all three tests are in good agreement with other published model solutions. It is shown that the use of the reduced grid does not significantly affect the accuracy up to the 25 % reduction in the number of grid points with respect to the regular grid. Variable resolution in latitude allows us to improve the accuracy of a solution in the region of interest.

scholarly journals Configuration and evaluation of a global unstructured mesh atmospheric model (GRIST-A20.9) based on the variable-resolution approach

2020 ◽  
Vol 13 (12) ◽  
pp. 6325-6348
Author(s):  
Yihui Zhou ◽  
Yi Zhang ◽  
Jian Li ◽  
Rucong Yu ◽  
Zhuang Liu
Keyword(s):  
Tropical Cyclone ◽  
Transition Zone ◽  
Unstructured Mesh ◽  
Climate Model ◽  
Model Performance ◽  
Atmospheric Model ◽  
Fine Scale ◽  
Variable Resolution ◽  
Scale Structures ◽  
Fine Resolution

Abstract. Targeting a long-term effort towards a variable-resolution (VR) global weather and climate model, this study systematically configures and evaluates an unstructured mesh atmospheric model based on the multiresolution approach. The model performance is examined from dry dynamics to simple physics and full physics scenarios. In the dry baroclinic wave test, the VR model reproduces comparable fine-scale structures in the refined regions as a fine-resolution quasi-uniform (QU) mesh model. The mesh transition zone does not adversely affect the wave pattern. Regional kinetic energy spectra show that the fine-scale resolving ability improves as the fine resolution increases. Compared to a QU counterpart that has equivalent degrees of freedom, the VR model tends to increase the global errors, but the errors can be reduced when the resolution of the coarse region is increased. The performance over the coarse region is generally close to that of a low-resolution QU counterpart. Two multi-region refinement approaches, the hierarchical and polycentric refinement modes, further validate the model performance under the multiresolution refinement. Activating hyperdiffusion for horizontal velocity is helpful with respect to VR modeling. An idealized tropical cyclone test is further used to examine its ability to resolve fine-scale structures. In the simple physics environment, the VR model can have the tropical cyclone stably pass the transition zone in various configurations. A series of sensitivity tests examines the model performance in a hierarchical refinement mode. The simulations exhibit consistency even when the VR mesh is slightly perturbed by one of the three parameters that control the density function. The tropical cyclone, starting from the second refinement region and passing through the inner transition zone, gets intensified and covers a smaller area in the refined regions. Such variations are consistent with the behavior that one may observe when uniformly refining the QU mesh. In the full physics environment with a highly variable mesh that reaches sub-10 km resolution, the VR model also produces a reasonable evolution for the tropical cyclone. The explicit diffusion shows its usefulness in terms of suppressing some unrealistic isolated-scale structures that are far away from the initial vortex and does not adversely affect the physically important object. The fine-scale structure is determined mainly by the fine-resolution area, although the systems may have larger differences before they move into the fine-resolution area. Altogether, this work demonstrates that the multiresolution configuration is a reliable and economic alternative to high-resolution global modeling. The adverse impact due to mesh transition and the coarse region can be controlled well.

scholarly journals A Multiscale Nonhydrostatic Atmospheric Model Using Centroidal Voronoi Tesselations and C-Grid Staggering

2012 ◽  
Vol 140 (9) ◽  
pp. 3090-3105 ◽  
Author(s):  
William C. Skamarock ◽  
Joseph B. Klemp ◽  
Michael G. Duda ◽  
Laura D. Fowler ◽  
Sang-Hun Park ◽  
...  
Keyword(s):  
Large Scale ◽  
Regional Climate ◽  
Time Integration ◽  
Atmospheric Model ◽  
Horizontal Resolution ◽  
Variable Resolution ◽  
Transition Zones ◽  
Voronoi Tesselations ◽  
Scale Models ◽  
Large Scale Flow

Abstract The formulation of a fully compressible nonhydrostatic atmospheric model called the Model for Prediction Across Scales–Atmosphere (MPAS-A) is described. The solver is discretized using centroidal Voronoi meshes and a C-grid staggering of the prognostic variables, and it incorporates a split-explicit time-integration technique used in many existing nonhydrostatic meso- and cloud-scale models. MPAS can be applied to the globe, over limited areas of the globe, and on Cartesian planes. The Voronoi meshes are unstructured grids that permit variable horizontal resolution. These meshes allow for applications beyond uniform-resolution NWP and climate prediction, in particular allowing embedded high-resolution regions to be used for regional NWP and regional climate applications. The rationales for aspects of this formulation are discussed, and results from tests for nonhydrostatic flows on Cartesian planes and for large-scale flow on the sphere are presented. The results indicate that the solver is as accurate as existing nonhydrostatic solvers for nonhydrostatic-scale flows, and has accuracy comparable to existing global models using icosahedral (hexagonal) meshes for large-scale flows in idealized tests. Preliminary full-physics forecast results indicate that the solver formulation is robust and that the variable-resolution-mesh solutions are well resolved and exhibit no obvious problems in the mesh-transition zones.

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