HR: 11:00h
AN: A32A-04    [Abstracts]
TI: Influence of domain size on RCM's internal variability
AU: * Lucas-Picher, P
EM: picher@sca.uqam.ca
AF: University of Quebec at Montreal, 550 Sherbrooke West, 19th floor, West tower, Montreal, QC H3A1B9 Canada
AU: Caya, D
EM: caya.daniel@ouranos.ca
AF: Ouranos, 550 Sherbrooke West, 19th floor, West tower, Montreal, QC H3A1B9 Canada
AU: Biner, S
EM: biner.sebastien@ouranos.ca
AF: Ouranos, 550 Sherbrooke West, 19th floor, West tower, Montreal, QC H3A1B9 Canada
AB: Pairs of simulations from the Canadian RCM (CRCM) using three different domain sizes are analyzed to investigate changes in internal variability with the increase of the integration domain. Members in the small ensembles differ only by a one-month lag in their initial conditions and all simulations cover a period of many years. As the domain increases, the weather systems stay longer in the RCM domain and the forcing from the lateral boundary conditions is then reduced. It was observed, in the larger domain, that the large-scale circulation differs sometimes between members of the ensemble and also from the one in the driving data. The internal variability in the larger domain reaches values comparable to the one in the driving GCM. Such a large internal variability requires an ensemble of simulations to cover the spectrum of possible solutions for a given set of lateral boundary conditions. Annual cycle of the root-mean-square-difference (RMSD) between pairs of simulations in the large domain shows that the winter RMSD is sometime higher than in summer. This result is different than the stronger RMSD values in summer showed in many studies (Giorgi and Bi, 2000, Christensen et al., 2001, Caya and Biner, 2004). Application of the spectral nudging technique to reduce internal variability for the largest domain is demonstrated in a last experiment. With this technique, the RCM large-scale circulation stays closer to the one of the driving data and this reduce the mismatch in large-scale circulation at the boundary outflow.
DE: 3337 Numerical modeling and data assimilation
DE: 4215 Climate and interannual variability (3309)
DE: 3319 General circulation
DE: 1620 Climate dynamics (3309)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting