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Decadal Regional Climate Studies and Applications with Variable-Resolution GCMs using Advanced Numerical Techniques

J. Côté, B. Denis, B. Dugas, S. Édouard, A. Qaddouri, K. Winger, RPN, Dorval
D. Caya, R. Laprise, R. De Elia, L. Spacek, UQAM, Montréal
Québec, Canada

Summary

This study is devoted to: research in parallel computing and numerical methods, atmospheric chemistry related to climate issues, validation of regional climate modeling strategies for nested- and stretched-grid models, decadal time-scale investigation with the Global Environmental (GEM) model, the limited-area version of GEM model experiments with the same regional resolution. This project reflects a trend in the modeling and broader communities to move towards regional and sub-regional assessments and applications important for the U.S. and Canadian public, business and policy decision makers, as well as for international collaborations on regional, and especially climate related issues. This study is done collaboration with M. Fox-Rabinovitz et al from the U. of Maryland.

The realizations fall into two categories: research in parallel computing and numerical methods, and applications to global and regional climate.

The research in parallel computing and numerical methods has led to the distributed memory version of the GEM model being ready to be implemented as an operational weather forecast model for North America. A crucial element was the use of solvers based on optimized matrix multiplication kernels. We are investigating efficient parallel iterative methods both for vector computers, which are operational until fall 2003 and the new scalar machine that will replace them. A new vertical coordinate system has been also developed for the GEM model. It has had a positive impact both for the large-scale stratospheric circulation and for the very short-scale atmospheric forecasts. A winter model climate has been produced using data from the National Centers for Environmental Prediction (NCEP) and compared to a control climate obtained using the previous version of the GEM model. This shows the benefit of the new vertical coordinates, which tend continuously to pressure surfaces in the stratosphere. New schemes to couple the physics to the dynamics in a way that maximizes accuracy while keeping the simplicity of separate steps were investigated.

In climate research, we have completed a new Atmospheric Model Intercomparison Project 2 (AMIP2) integration and have begun the "Stretched Grid Model Inter-comparison Project" (SGMIP). We are also starting another series of comparisons between limited-area (LAM) and stretched-grid versions of GEM. The goal is to provide us with a comparison of the limited-area and variable-resolution version of GEM for regional climate simulation. We are also evaluating the downscaling ability of one-way nested regional climate models. A rigorous and well-defined experiment called the Big-Brother Experiment (BBE) was developed for addressing some important one-way nesting issues. First, we developed a scale decomposition tool employed for the BBE. Second, the results showed that the Canadian Regional Climate Model (RCM) one-way nesting approach was reliable. The BBE was also used to investigate the sensitivity of an RCM to the spatial resolution and temporal update frequency of the lateral boundary conditions. We also studied the forecasting skill limits of nested LAMs, downscaling in mountainous region and internal variability in nested RCM as can be seen from the bibliography.

In the next year or two, we plan to do research on iterative methods for massively parallel computers with performance in the Teraflops range. We will be working on conservative semi-Lagrangian methods that would be applicable to atmospheric chemistry and the climate, and on the numerical validation of regional climate simulation techniques. Our interactions with other teams of SciDAC have been mainly though specialized workshops such as “Partial Differential Equation on the Sphere” and the Canadian Regional Climate Modeling Meeting. We have close contacts with the joint team at the U. of Maryland and with the Program for Climate Model Diagnosis and Intercomparison (PCMDI) team at Lawrence Livermore National Laboratory which is responsible for the AMIP2 project.

References

Yeh, K.-S., J. Côté, S. Gravel, A. Méthot, A. Patoine, M. Roch and A. Staniforth, 2002: The Operational CMC-MRB Global Environmental Multiscale (GEM) Model. Part III: Nonhydrostatic formulation. Mon. Wea. Rev., 130, 339-356.
Denis, B., J. Côté ,and R. Laprise, 2002: Spectral decomposition of non-periodic two-dimensional atmospheric fields using the discrete cosine transform (DCT). Mon. Wea. Rev., 130, 1812-1829.
Denis, B., R. Laprise, D. Caya and J. Côté, 2002: Downscaling ability of one-way nested regional climate models: The Big-Brother Experiment. Clim. Dyn. 18:627-646.
Erfani, A., A. Méthot, R. Goodson, S. Bélair, K.-S. Yeh, J. Côté and R. Moffet, 2003: Synoptic and mesoscale study of a severe convective outbreak with the non-hydrostatic Global Environmental Multiscale (GEM) model. Meteor. Atmos. Phys. (in press).
Denis, B., R. Laprise and D. Caya, 2002: Sensitivity of One-way Nested Regional Climate Models to the spatial and temporal resolutions of the lateral boundary conditions. Clim. Dyn. (in press).
de Elía, R., R. Laprise and B. Denis, 2002: Forecast skill limits of nested, limited-area models: A perfect-model approach. Mon. Wea. Rev., 130, 2006-2023.
Staniforth, A., N. Wood and J. Côté, 2002: A simple comparison of four physics-dynamics coupling schemes. Mon. Wea. Rev., 130, 3129-3135.
Staniforth, A., N. Wood and J. Côté, 2002: Analysis of the numerics of physics-dynamics coupling. Q. J. R. Meteorol. Soc. 128, 2779-2799.
Caya, D. and S. Biner: Internal Variability of RCM Simulations Over an Annual Cycle. Submitted to Clim. Dyn
Qaddouri, A., J. Côté, 2002: Preconditioning for an iterative elliptic solver on a vector processor. Proceedings of the 5^th Int. Meeting in High Performance Computing for Computational Science (VECPAR’2002), June 26-28, Porto, Portugal.

For further information on this subject contact:

Dr. Jean Côté, Numerical Method Group
Recherche en prévision numérique
Phone 514-421-4742
jean.cote@ec.gc.ca

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