Temporal and spatial scales of precipitation as simulated by the CRCM
A. Di Luca 1,3, R. de Elía 2,3 and R. Laprise 1,3
Université du Québec à Montréal, Montréal, Canada;
2
Ouranos Consortium, Montréal, Canada
3
Centre ESCER (Etude et Simulation du Climat à l’Échelle Régionale), Montréal, Canada
1
Regional climate models (RCMs) are developed with the aim of representing fine scale
structures that are absent in the atmospheric fields simulated by a coarse-resolution coupled
general circulation models (CGCMs). The RCM–simulated small scales represent the main
potential added value of the high-resolution RCM over the CGCM. The explicit treatment of
some mesoscale processes with the increased resolution could produce an improvement of the
large scales but this not appears to be the case. Several studies suggest that the RCM produce
no modification or even degradation of the driven large scales (see Laprise et al. 2008 and
references therein). As a result, the presence of fine scale details in the climate variable to be
analyzed seems to constitute a necessary condition for the potential added value to become
effective.
As can be shown, small scales features are not necessarily present in RCM simulated variables
(e.g., monthly mean precipitation in the middle of the Pacific Ocean). The existence of fine scale
details depends on a variety of factors related to atmospheric and physical forcings, among
them: the climate variable analised, the surface forcings that characterizes the region of study
(e.g., complex topography, land-sea contrasts, etc), and the weather regime (e.g., convective or
stratiform precipitation) from which the statistic is calculated.
This presentation will address the dependence of fine scale features (both spatial and temporal)
in RCM simulated precipitation by considering different statistics. Spatio-temporal behaviour of
precipitation is investigated by analyzing time and space averages at different scales in several
regions across Canada. The precipitation data used in this study was simulated by the Canadian
Regional Climate Model (CRCM).