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America, both driven ERA40 and AMIP2 are compared with
observations. CRU2 data are used for precipitation and
minimum and maximum (not shown) screen temperature.
Preliminary results show that CRCM5 produces an
acceptable climate over North America, with, as usual, some
improvements and some deteriorations compared to
CRCM4, depending on the variable, the region and the
season. For instance, precipitation is less noisy over the
Rockies, compared with CRCM4 (see Fig. 2). The typical
problematic under-representation by most regional models
(as preliminary results from NARCCAP suggest) of
Mississippi delta winter precipitation does not seem to
appear in CRCM5. Summer maximum screen temperature
has a slightly reduced warm bias compared to CRCM4,
albeit over a different region, while minimum screen
temperature warm biases have increased (see Fig. 3). For
winter, a warm minimum screen temperature bias (4-5º)
located specifically over boreal forest in Canada is
particularly notable and may be related to snow formulation
in ISBA or to geophysical characteristics (to be confirmed).
however not without some remaining challenges. Boreal
forest in winter seems particularly problematic.
Figure 3. CRCM4 and CRCM5 1961-2000 DJF
minimum screen temperature difference with CRU2
(°C).
References
Biner, S., D. Caya, R. Laprise and L. Spacek, Nesting of
RCMs by Imposing Large scales. Research Activities
in Atmospheric and Oceanic Modelling, Ed. H.
Ritchie. Report N 30, WMO/TD No 987, pp. 7.3-7.4,
2000.
Laprise, R., D. Caya, G. Bergeron and M. Giguère, The
formulation of André Robert MC2 (Mesoscale
Compressible Community) model. Atmos.-Ocean,
Vol. 35, No. 1, pp. 195-220, 1997.
Figure 2. CRCM4 and CRCM5 1961-2000 DJF
precipitation difference with CRU2 (mm/d).
5. Conclusion
A new version of the CRCM (CRCM5) is under
development. For now, only the NWP physics coupling with
the dynamics is done, while the CGCM4 climate physics
coupling is still under way. For now, 40-year recent past
(1961-2000) climate simulations for both operational
(CRCM4) and developmental (CRCM5) versions are
compared with observations. First results with CRCM5 are
promising, particularly for precipitation and radiation,
Plummer D. A., D. Caya, A. Frigon, H. Côté, M. Giguère,
D. Paquin, S. Biner, R. Harvey, R. de Elia, Climate
Change over North America as Simulated by the
Canadian RCM. Journal of Climate. Vol 19, No 13,
pp. 3112-3132, 2006.
Scinocca, J. F., N. A. McFarlane, M. Lazare, J. Li, and D.
Plummer, The CCCma third generation AGCM and its
extension into the middle atmosphere. Atmos. Chem.
Phys. Discuss., Vol. 8, pp. 7883-7930, 2008.
Zadra A., D. Caya, J. Côté, B. Dugas, C. Jones, R.
Laprise, K. Winger and L.-P. Caron, The next
Canadian Regional Climate Model. Physics in
Canada, Vol. 64, No. 2, pp. 75-83, 2008.