Two-way nesting ocean models with different vertical coordinates

2021 ◽  
Author(s):  
Jerome Chanut ◽  
James Harle ◽  
Tim Graham ◽  
Laurent Debreu
Keyword(s):  
Vertical Direction ◽  
Test Cases ◽  
Numerical Representation ◽  
Arbitrary Lagrangian Eulerian ◽  
Coordinate Systems ◽  
Vertical Coordinate ◽  
Terrain Following ◽  
New Feature ◽  
Polynomial Reconstruction ◽  
Horizontal Grid

<p>The NEMO platform possesses a versatile block-structured refinement capacity thanks to the AGRIF library. It is however restricted up to versions 4.0x, to the horizontal direction only. In the present work, we explain how we extended the nesting capabilities to the vertical direction, a feature which can appear, in some circumstances, as beneficial as refining the horizontal grid.</p><p>Doing so is not a new concept per se, except that we consider here the general case of child and parent grids with possibly different vertical coordinate systems, hence not logically defined from each other as in previous works. This enables connecting together for instance z (geopotential), s (terrain following) or eventually ALE (Arbitrary Lagrangian Eulerian) coordinate systems. In any cases, two-way exchanges are enabled, which is the other novel aspect tackled here.  </p><p>Considering the vertical nesting procedure itself, we describe the use of high order conservative and monotone polynomial reconstruction operators to remap from parent to child grids and vice versa. Test cases showing the feasibility of the approach are presented, with particular attention on the connection of s and z grids in the context of gravity flow modelling. This work can be considered as a preliminary step towards the application of the vertical nesting concept over major overflow regions in global realistic configurations. The numerical representation of these areas is indeed known to be particularly sensitive to the vertical coordinate formulation. More generally, this work illustrates the typical methodology from the development to the validation of a new feature in the NEMO model.</p>

On the Use of an Adaptive, Hybrid-Isentropic Vertical Coordinate in Global Atmospheric Modeling

2010 ◽  
Vol 138 (6) ◽  
pp. 2188-2210 ◽  
Author(s):  
Rainer Bleck ◽  
Stan Benjamin ◽  
Jin Lee ◽  
Alexander E. MacDonald
Keyword(s):  
Hybrid Approach ◽  
Atmospheric Modeling ◽  
Arbitrary Lagrangian Eulerian ◽  
Free Atmosphere ◽  
Vertical Coordinate ◽  
Trade Offs ◽  
Terrain Following ◽  
Spatial Transition ◽  
The Impact

Abstract This article is one in a series describing the functionality of the Flow-Following, Finite-Volume Icosahedral Model (FIM) developed at NOAA’s Earth System Research Laboratory. Emphasis in this article is on the design of the vertical coordinate—the “flow following” aspect of FIM. The coordinate is terrain-following near the ground and isentropic in the free atmosphere. The spatial transition between the two coordinates is adaptive and is based on the arbitrary Lagrangian–Eulerian (ALE) paradigm. The impact of vertical resolution trade-offs between the present hybrid approach and traditional terrain-following coordinates is demonstrated in a three-part case study.

A Control-Volume Model of the Compressible Euler Equations with a Vertical Lagrangian Coordinate

2013 ◽  
Vol 141 (7) ◽  
pp. 2526-2544 ◽  
Author(s):  
Xi Chen ◽  
Natalia Andronova ◽  
Bram Van Leer ◽  
Joyce E. Penner ◽  
John P. Boyd ◽  
...  
Keyword(s):  
Euler Equations ◽  
Control Volume ◽  
Test Cases ◽  
Riemann Solver ◽  
New Approach ◽  
Vertical Coordinate ◽  
Low Mach Number ◽  
Atmospheric Flows ◽  
Lagrangian Coordinate ◽  
Control Volume Approach

Abstract Accurate 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.

Numerical Simulations of Nonlinear Post-Critical Vibrations of an Airfoil After Flutter Instability

2011 ◽  
Author(s):  
Jaromi´r Hora´cˇek ◽  
Miloslav Feistauer ◽  
Petr Sva´cˇek
Keyword(s):  
Numerical Simulations ◽  
Degrees Of Freedom ◽  
Stokes Equations ◽  
Mass Matrix ◽  
Vertical Direction ◽  
Navier Stokes ◽  
Computational Domain ◽  
Arbitrary Lagrangian Eulerian ◽  
Navier Stokes Equations ◽  
Classical Flutter

The contribution deals with the numerical simulation of the flutter of an airfoil with three degrees of freedom (3-DOF) for rotation around an elastic axis, oscillation in the vertical direction and rotation of a flap. The finite element (FE) solution of two-dimensional (2-D) incompressible Navier-Stokes equations is coupled with a system of nonlinear ordinary differential equations describing the airfoil vibrations with large amplitudes taking into account the nonlinear mass matrix. The time-dependent computational domain and a moving grid are treated by the Arbitrary Lagrangian-Eulerian (ALE) method and a suitable stabilization of the FE discretization is applied. The developed method was successfully tested by the classical flutter computation of the critical flutter velocity using NASTRAN program considering the linear model of vibrations and the double-lattice aerodynamic theory. The method was applied to the numerical simulations of the post flutter regime in time domain showing Limit Cycle Oscillations (LCO) due to nonlinearities of the flow model and vibrations with large amplitudes. Numerical experiments were performed for the airfoil NACA 0012 respecting the effect of the air space between the flap and the main airfoil.

Jacobian mapping between vertical coordinate systems in data assimilation

2007 ◽  
Vol 133 (627) ◽  
pp. 1547-1558 ◽  
Author(s):  
Y. J. Rochon ◽  
L. Garand ◽  
D. S. Turner ◽  
S. Polavarapu
Keyword(s):  
Data Assimilation ◽  
Coordinate Systems ◽  
Vertical Coordinate

A New Terrain-Following Vertical Coordinate Formulation for Atmospheric Prediction Models

2002 ◽  
Vol 130 (10) ◽  
pp. 2459-2480 ◽  
Author(s):  
Christoph Schär ◽  
Daniel Leuenberger ◽  
Oliver Fuhrer ◽  
Daniel Lüthi ◽  
Claude Girard
Keyword(s):  
Prediction Models ◽  
Vertical Coordinate ◽  
Terrain Following

scholarly journals The Finite-volumE Sea ice–Ocean Model (FESOM2)

2016 ◽  
Author(s):  
Sergey Danilov ◽  
Dmitry Sidorenko ◽  
Qiang Wang ◽  
Thomas Jung
Keyword(s):  
Sea Ice ◽  
Ocean Circulation ◽  
Unstructured Mesh ◽  
Circulation Model ◽  
Ocean Model ◽  
Arbitrary Lagrangian Eulerian ◽  
Major Step ◽  
Vertical Coordinate ◽  
Intercomparison Project ◽  
Mesh Models

Abstract. Version 2 of the unstructured-mesh sea ice – ocean circulation model FESOM is presented. It builds upon FESOM1.4 (Wang et al., 2014, Geosci. Mod. Dev., 7, 663–693) but differs by its dynamical core (finite volumes instead of finite elements) and is formulated using the Arbitrary Lagrangian Eulerian (ALE) vertical coordinate, which increases model flexibility. The model inherits the framework and sea ice model from the previous version, which minimizes the efforts needed from a user to switch from one version to the other. The ocean states simulated with FESOM1.4 and FESOM2.0 driven by CORE-II forcing are compared on a mesh used for CORE-II intercomparison project. Additionally the performance on an eddy-permitting mesh with uniform resolution is discussed. The new version improves numerical efficiency of FESOM in terms of CPU time by at least three times while retaining its fidelity in simulating sea ice and ocean. From this it is argued that FESOM2.0 provides a major step forward in establishing unstructured-mesh models as valuable tools in climate research.

scholarly journals Improvement of Mountain-Wave Turbulence Forecasts in NOAA’s Rapid Refresh (RAP) Model with the Hybrid Vertical Coordinate System

2019 ◽  
Vol 34 (3) ◽  
pp. 773-780 ◽  
Author(s):  
Jung-Hoon Kim ◽  
Robert D. Sharman ◽  
Stanley G. Benjamin ◽  
John M. Brown ◽  
Sang-Hun Park ◽  
...  
Keyword(s):  
North America ◽  
Coordinate System ◽  
Weather Prediction ◽  
Energy Dissipation Rate ◽  
Small Scale ◽  
False Alarms ◽  
Mountain Wave ◽  
Vertical Coordinate ◽  
Terrain Following ◽  
Scale Turbulence

Abstract Spurious mountain-wave features have been reported as false alarms of light-or-stronger numerical weather prediction (NWP)-based cruise level turbulence forecasts especially over the western mountainous region of North America. To reduce this problem, a hybrid sigma–pressure vertical coordinate system was implemented in NOAA’s operational Rapid Refresh model, version 4 (RAPv4), which has been running in parallel with the conventional terrain-following coordinate system of RAP version 3 (RAPv3). Direct comparison of vertical velocity |w| fields from the RAPv4 and RAPv3 models shows that the new RAPv4 model significantly reduces small-scale spurious vertical velocities induced by the conventional terrain-following coordinate system in the RAPv3. For aircraft-scale turbulence forecasts, |w| and |w|/Richardson number (|w|/Ri) derived from both the RAPv4 and RAPv3 models are converted into energy dissipation rate (EDR) estimates. Then, those EDR-scaled indices are evaluated using more than 1.2 million in situ EDR turbulence reports from commercial aircraft for 4 months (September–December 2017). Scores of the area under receiver operating characteristic curves for the |w|- and |w|/Ri-based EDR forecasts from the RAPv4 are 0.69 and 0.83, which is statistically significantly improved over the RAPv3 of 0.63 and 0.77, respectively. The new RAPv4 became operational on 12 July 2018 and provides better guidance for operational turbulence forecasting over North America.

scholarly journals CELLS v1.0: updated and parallelized version of an electrical scheme to simulate multiple electrified clouds and flashes over large domains

2011 ◽  
Vol 4 (4) ◽  
pp. 2849-2892 ◽  
Author(s):  
C. Barthe ◽  
M. Chong ◽  
J.-P. Pinty ◽  
C. Bovalo ◽  
J. Escobar
Keyword(s):  
Negative Ions ◽  
Lightning Flash ◽  
Cloud Particle ◽  
Vertical Extension ◽  
Terrain Following ◽  
Parallel Code ◽  
New Feature ◽  
Convective Cells ◽  
Electrically Charged ◽  
Large Domains

Abstract. The paper describes the fully parallelized electrical scheme CELLS which is suitable to simulate explicitly electrified storm systems on parallel computers. Our motivation here is to show that a cloud electricity scheme can be developed for use on large grids with complex terrain. Large computational domains are needed to perform real case meteorological simulations with many independent convective cells. The scheme computes the bulk electric charge attached to each cloud particle. Positive and negative ions are also taken into account. Several parametrizations of the dominant non-inductive charging process are included and an inductive charging process as well. The electric field is obtained by inverting the Gauss equation with an extension to terrain-following coordinates. The new feature concerns the lightning flash scheme which is a simplified version of an older detailed sequential scheme. Flashes are composed of a bidirectional leader phase (vertical extension from the triggering point) and a phase obeying a fractal law (with horizontal extension on electrically charged zones). The originality of the scheme lies in the way the branching phase is treated to get a parallel code. The complete electrification scheme is tested for the 10 July 1996 STERAO case and for the 21 July 1998 EULINOX case. Flash characteristics are analysed in detail and additional sensitivity experiments are performed for the STERAO case. Although the simulations were run for flat terrain conditions, they show that the model behaves well on multiprocessor computers. This opens a wide area of application for this electrical scheme with the next objective of running real meteorological case on large domains.

An Evaluation of a Hybrid, Terrain-Following Vertical Coordinate in the WRF-Based RAP and HRRR Models

2020 ◽  
Vol 35 (3) ◽  
pp. 1081-1096 ◽  
Author(s):  
Jeffrey Beck ◽  
John Brown ◽  
Jimy Dudhia ◽  
David Gill ◽  
Tracy Hertneky ◽  
...  
Keyword(s):  
Complex Terrain ◽  
Wrf Model ◽  
Vertical Motion ◽  
Weather Research And Forecasting ◽  
Mountainous Terrain ◽  
Vertical Coordinate ◽  
Numerical Noise ◽  
Terrain Following ◽  
Model Equations ◽  
Real Time Simulations

Abstract A new hybrid, sigma-pressure vertical coordinate was recently added to the Weather Research and Forecasting (WRF) Model in an effort to reduce numerical noise in the model equations near complex terrain. Testing of this hybrid, terrain-following coordinate was undertaken in the WRF-based Rapid Refresh (RAP) and High-Resolution Rapid Refresh (HRRR) models to assess impacts on retrospective and real-time simulations. Initial cold-start simulations indicated that the majority of differences between the hybrid and traditional sigma coordinate were confined to regions downstream of mountainous terrain and focused in the upper levels. Week-long retrospective simulations generally resulted in small improvements for the RAP, and a neutral impact in the HRRR when the hybrid coordinate was used. However, one possibility is that the inclusion of data assimilation in the experiments may have minimized differences between the vertical coordinates. Finally, analysis of turbulence forecasts with the new hybrid coordinate indicate a significant reduction in spurious vertical motion over the full length of the Rocky Mountains. Overall, the results indicate a potential to improve forecast metrics through implementation of the hybrid coordinate, particularly at upper levels, and downstream of complex terrain.

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