**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 Elía, L. Spacek, UQÀM, 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 Univ. of Maryland.***

The research has led to the distributed memory version of the Global
Environmental Multiscale (GEM) model being implemented as an operational
weather forecast model for North America. It is now evaluated for
forecast at 15 km rather that 24 km, almost doubling the number of
degrees of freedom. A crucial element was the use of solvers based on
optimized matrix multiplication kernels. We have been also investigating
efficient parallel iterative methods. The hybrid vertical coordinate
system for the GEM model has been further tested and implemented both
for global and mesoscale modeling.

We have completed the first phase of the international Streched Grid
Model Intercomparison Project (SGMIP) as well the first multi-year
preliminary simulation with a Limited Area Model (LAM) version of our
GEM model. Results from these two simulations have been compared to a
very recent Atmospheric Model Intercomparison
![](media/image1.png){width="2.995833333333333in"
height="2.3152777777777778in"}*Figure 1. The mean precipitation field
for January obtained in the Stretched Grid Model Inter-comparison
Project simulation.*

Project 2 (AMIP2) uniform global simulation of the same model. SGMIP and
LAM had a maximum resolution of 0.45° over North-America (NA), while
AMIP2 was performed at 1.5°. The AMIP2 and SGMIP climates turn out to be
very similar and the differences between the two can be usually be
traced to the increased resolution over North America, especially near
the surface and at the tropopause level.

The LAM and SGMIP also show similar surface results, although more works
needs to be done over the LAM\'s nesting areas. A more comprehensive
comparison will shortly be done of the three model configurations in a
further investigation of one- and two-way nesting strategies with the
Big Brother Experimental Setup, which is a rigorous and well-defined
experiment used for addressing some important one-way nesting issues.

In the next year or two, we plan to continue research on iterative
methods for massively parallel computers with performance in the
Teraflops range. We intend to pursue the second phase of the
international Stretched Grid Intercomparison Project (SGMIP) initiated
by our collaborator M. Fox-Rabinovitz. 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.

Reference

Caya, D., and S. Biner, 2003: Internal variability of RCM simulations
over an annual cycle. *Climate Dyn.*, **24**, 33-46.

de Elía, R., and R. Laprise, 2003: Predictability of Limited-Area
Models: Twin and Big-Brother Experiments. *Research activities in
Atmospheric and Oceanic Modelling, WMO/TD*, J. Côté, Ed., 1161 (33):
5.7-5.8.

Denis, B., R. Laprise, and D. Caya, 2003: Sensitivity of a regional
climate model to the resolution of the lateral boundary conditions.
*Climate Dyn.*, **20**, 107-126.

Édouard, S, B. Dugas, 2003: The Use of a hybrid vertical coordinate in
the CMC-MRB Global Environnemental Model (GEM) model. *Research
activities in Atmospheric and Oceanic Modelling, WMO/TD*, J. Côté, Ed.,
1161 (33): 6.3-6.4.

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.* **82**, 31-53.

Laprise, R., 2003: Resolved scales and nonlinear interactions in
limited-area models. *J. Atmos. Sci.*, 60, 768-779.

Lucas-Picher, P., D. Caya, S. Biner, 2004: RCM's internal variability as
function of domain size. *Research activities in Atmospheric and Oceanic
Modelling, WMO/TD*, J. Côté, Ed., (34), 2 pages.

Qaddouri, A., and J. Côté, 2003: Preconditioning for an iterative
elliptic solver on a vector processor. *High Performance Computing for
Computational Science* -VECPAR'2002, Springer, Palma, Dongarra,
Hernandez and Sousa Eds, 343-353.

Qaddouri, A., and J. Côté, 2004: Optimization of a direct elliptic
boundary value problem solver by the combined use of symmetry and
Strassen's algorithm. Accepted by *Mon. Wea. Rev.*.

**For further information on this subject contact:**

Dr. Jean Côté, Recherche en prévision numérique

2121 Trans-Canada Highway

Dorval, QC Canada, H9P 1J3

Phone 514-421-4742

<jean.cote@ec.gc.ca>