A Limited Area Modeling Capability for the Finite‐Volume Cubed‐Sphere (FV3) Dynamical Core and Comparison with a Global Two‐Way Nest

AbstractVerification methods for convection-allowing models (CAMs) should consider the finescale spatial and temporal detail provided by CAMs, and including both neighborhood and object-based methods can account for displaced features that may still provide useful information. This work explores both contingency table–based verification techniques and object-based verification techniques as they relate to forecasts of severe convection. Two key fields in severe weather forecasting are investigated: updraft helicity (UH) and simulated composite reflectivity. UH is used to generate severe weather probabilities called surrogate severe fields, which have two tunable parameters: the UH threshold and the smoothing level. Probabilities computed using the UH threshold and smoothing level that give the best area under the receiver operating curve result in very high probabilities, while optimizing the parameters based on the Brier score reliability component results in much lower probabilities. Subjective ratings from participants in the 2018 NOAA Hazardous Weather Testbed Spring Forecasting Experiment (SFE) provide a complementary evaluation source. This work compares the verification methodologies in the context of three CAMs using the Finite-Volume Cubed-Sphere Dynamical Core (FV3), which will be the foundation of the U.S. Unified Forecast System (UFS). Three agencies ran FV3-based CAMs during the five-week 2018 SFE. These FV3-based CAMs are verified alongside a current operational CAM, the High-Resolution Rapid Refresh version 3 (HRRRv3). The HRRR is planned to eventually use the FV3 dynamical core as part of the UFS; as such evaluations relative to current HRRR configurations are imperative to maintaining high forecast quality and informing future implementation decisions.

Download Full-text

A Two-Way Nested Global-Regional Dynamical Core on the Cubed-Sphere Grid

Monthly Weather Review ◽

10.1175/mwr-d-11-00201.1 ◽

2013 ◽

Vol 141 (1) ◽

pp. 283-306 ◽

Cited By ~ 66

Author(s):

Lucas M. Harris ◽

Shian-Jiann Lin

Keyword(s):

Finite Volume ◽

Large Scale ◽

Wave Train ◽

Mass Conservation ◽

Volume Averaging ◽

Test Case ◽

Geophysical Fluid Dynamics Laboratory ◽

Dynamical Core ◽

Nested Grid ◽

Cubed Sphere

Abstract A nested-grid model is constructed using the Geophysical Fluid Dynamics Laboratory finite-volume dynamical core on the cubed sphere. The use of a global grid avoids the need for externally imposed lateral boundary conditions, and the use of the same governing equations and discretization on the global and regional domains prevents inconsistencies that may arise when these differ between grids. A simple interpolated nested-grid boundary condition is used, and two-way updates use a finite-volume averaging method. Mass conservation is achieved in two-way nesting by simply not updating the mass field. Despite the simplicity of the nesting methodology, the distortion of the large-scale flow by the nested grid is such that the increase in global error norms is a factor of 2 or less in shallow-water test cases. The effect of a nested grid in the tropics on the zonal means and eddy statistics of an idealized Held–Suarez climate integration is minor, and artifacts due to the nested grid are comparable to those at the edges of the cubed-sphere grid and decrease with increasing resolution. The baroclinic wave train in a Jablonowski–Williamson test case was preserved in a nested-grid simulation while finescale features were represented with greater detail in the nested-grid region. The authors also found that lee vortices could propagate out of the nested region and onto a coarse grid, which by itself could not produce vortices. Finally, the authors discuss how concurrent integration of the nested and coarse grids can be significantly more efficient than when integrating the two grids sequentially.

Download Full-text

The LMARS based shallow-water dynamical core on the cubed-sphere geometry

10.1002/essoar.10503974.1 ◽

2020 ◽

Author(s):

Xi Chen

Keyword(s):

Shallow Water ◽

Dynamical Core ◽

Sphere Geometry ◽

Cubed Sphere

Download Full-text

Transport Schemes in GungHo

10.5194/egusphere-egu21-2743 ◽

2021 ◽

Author(s):

James Kent

Keyword(s):

Finite Element ◽

Finite Volume ◽

Mixed Finite Element ◽

Method Of Lines ◽

Finite Volume Methods ◽

Kutta Method ◽

Finite Volume Schemes ◽

Dynamical Core ◽

Runge Kutta Method ◽

The Stability

<p>GungHo is the mixed finite-element dynamical core under development by the Met Office. A key component of the dynamical core is the transport scheme, which advects density, temperature, moisture, and the winds, throughout the atmosphere. Transport in GungHo is performed by finite-volume methods, to ensure conservation of certain quantaties. There are a range of different finite-volume schemes being considered for transport, including the Runge-Kutta/method-of-lines and COSMIC/Lin-Rood schemes. Additional horizontal/vertical splitting approaches are also under consideration, to improve the stability aspects of the model. Here we discuss these transport options and present results from the GungHo framework, featuring both prescribed velocity advection tests and full dry dynamical core tests.&#160;</p>

Download Full-text

Towards an Unstaggered Finite‐Volume Dynamical Core With a Fast Riemann Solver: 1‐D Linearized Analysis of Dissipation, Dispersion, and Noise Control

Journal of Advances in Modeling Earth Systems ◽

10.1029/2018ms001361 ◽

2018 ◽

Vol 10 (9) ◽

pp. 2333-2356 ◽

Cited By ~ 2

Author(s):

Xi Chen ◽

Shiann‐Jiann Lin ◽

Lucas M. Harris

Keyword(s):

Finite Volume ◽

Noise Control ◽

Riemann Solver ◽

Dynamical Core

Download Full-text

A mimetic, semi-implicit, forward-in-time, finite volume shallow water model: comparison of hexagonal–icosahedral and cubed-sphere grids

Geoscientific Model Development ◽

10.5194/gmd-7-909-2014 ◽

2014 ◽

Vol 7 (3) ◽

pp. 909-929 ◽

Cited By ~ 26

Author(s):

J. Thuburn ◽

C. J. Cotter ◽

T. Dubos

Keyword(s):

Shallow Water ◽

Finite Volume ◽

Model Comparison ◽

Mass Conservation ◽

Time Discretization ◽

Water Model ◽

Tracer Transport ◽

Exact Mass ◽

Large Wave ◽

Cubed Sphere

Abstract. A new algorithm is presented for the solution of the shallow water equations on quasi-uniform spherical grids. It combines a mimetic finite volume spatial discretization with a Crank–Nicolson time discretization of fast waves and an accurate and conservative forward-in-time advection scheme for mass and potential vorticity (PV). The algorithm is implemented and tested on two families of grids: hexagonal–icosahedral Voronoi grids, and modified equiangular cubed-sphere grids. Results of a variety of tests are presented, including convergence of the discrete scalar Laplacian and Coriolis operators, advection, solid body rotation, flow over an isolated mountain, and a barotropically unstable jet. The results confirm a number of desirable properties for which the scheme was designed: exact mass conservation, very good available energy and potential enstrophy conservation, consistent mass, PV and tracer transport, and good preservation of balance including vanishing ∇ × ∇, steady geostrophic modes, and accurate PV advection. The scheme is stable for large wave Courant numbers and advective Courant numbers up to about 1. In the most idealized tests the overall accuracy of the scheme appears to be limited by the accuracy of the Coriolis and other mimetic spatial operators, particularly on the cubed-sphere grid. On the hexagonal grid there is no evidence for damaging effects of computational Rossby modes, despite attempts to force them explicitly.

Download Full-text

A Multimoment Constrained Finite-Volume Model for Nonhydrostatic Atmospheric Dynamics

Monthly Weather Review ◽

10.1175/mwr-d-12-00144.1 ◽

2013 ◽

Vol 141 (4) ◽

pp. 1216-1240 ◽

Cited By ~ 20

Author(s):

Xingliang Li ◽

Chungang Chen ◽

Xueshun Shen ◽

Feng Xiao

Keyword(s):

Finite Volume ◽

Evolution Equations ◽

Complex Geometry ◽

High Order ◽

Computationally Efficient ◽

Dynamical Core ◽

Benchmark Tests ◽

Volume Method ◽

Further Development ◽

Mesh Cell

Abstract The two-dimensional nonhydrostatic compressible dynamical core for the atmosphere has been developed by using a new nodal-type high-order conservative method, the so-called multimoment constrained finite-volume (MCV) method. Different from the conventional finite-volume method, the predicted variables (unknowns) in an MCV scheme are the values at the solution points distributed within each mesh cell. The time evolution equations to update the unknown point values are derived from a set of constraint conditions based on the multimoment concept, where the constraint on the volume-integrated average (VIA) for each mesh cell is cast into a flux form and thus guarantees rigorously the numerical conservation. Two important features make the MCV method particularly attractive as an accurate and practical numerical framework for atmospheric and oceanic modeling. 1) The predicted variables are the nodal values at the solution points that can be flexibly located within a mesh cell (equidistant solution points are used in the present model). It is computationally efficient and provides great convenience in dealing with complex geometry and source terms. 2) High-order and physically consistent formulations can be built by choosing proper constraints in view of not only numerical accuracy and efficiency but also underlying physics. In this paper the authors present a dynamical core that uses the third- and the fourth-order MCV schemes. They have verified the numerical outputs of both schemes by widely used standard benchmark tests and obtained competitive results. The present numerical core provides a promising and practical framework for further development of nonhydrostatic compressible atmospheric models.

Download Full-text