Revista Brasileira de Meteorologia
Print version ISSN 0102-7786
VALVERDE, María C and MARENGO, José A. Changes in the atmospheric circulation pattern over South America in future climate scenarios derived from the IPCC AR4 model climate simulations. Rev. bras. meteorol. [online]. 2010, vol.25, n.1, pp. 125-145. ISSN 0102-7786. http://dx.doi.org/10.1590/S0102-77862010000100011.
In this paper changes in the atmospheric circulation that may occur in the South America (SA) as a consequence of climate change were studied for various emission scenarios. Five global models from IPCC AR4 (CCCMA, GFDL, HadCM3, MIROC and GISS) are used, for 1961-1990 (present climate) from the 20C3M model run, and for 2011-2100 for the SRES A2 high emission scenario. For the future, (2011-2040, 2041-2070 and 2071-2100 time periods), in most of the models (except the MIROC), the thermal continental low (Chaco low) is shifted to the southwest while the Bolivian High is northwest shifted during in the summer and spring. All the models show, for present climate simulation a weak subtropical southeast Pacific anticyclone (SPA), which would induce a reduction atmospheric subsidence. When the anticyclone is shifted southward, it would be linked with a stronger and more southward Pacific ITCZ. For the future climate, only two models (HadCM3 and GISS) showaweakerSPAascomparedtothepresent. Ontheotherhand,thesubtropicalsouthwestAtlantic anticyclone (SAA) seems to be more intense during fall and winter in almost all models (with the exception of the GISS model). Among the different models, the HadCM3 simulates the summer and spring circulation close to NCEP Reanalysis. This model does exhibit a relatively well simulated SACZ, contributing with a decrease of precipitation over Amazon. Moreover, for the future scenarios the HadCM3 model shows changes in rainfall patterns, with positive anomalies over the West Coast of Peru and Equator and negative anomalies over Northeast of Brazil, and Eastern of Amazon, linked to weaker and southward shifted South Pacific High, enforcing the ITCZ over 5ºS, as a consequence of a decrease of the moisture convergence over Amazon.
Keywords : Climatic changes; IPCC AR4 models; Circulation Pattern; future scenarios.