Abstract
Historical simulations (present climate) and projections under RCP8.5 scenario (future climate) by HadGEM2-ES of temperature and precipitation are analyzed during the four seasons in South America. Projections of precipitation are discussed in terms of atmospheric circulation. The South Atlantic Convergence Zone (SACZ) and the Pacific South America (PSA) patterns are analyzed in simulations of present climate and in future climate projections. The model shows small systematic errors over South America, larger close to the northern South American coast in DJF and MAM. The seasonal variability of precipitation, temperature and wind fields is very well reproduced, mainly the summer/winter differences. The SACZ and the Intertropical Convergence Zone (ITCZ) are well simulated. The good model performance to reproduce the precipitation, temperature and wind fields, in the present climate, gives confidence in the projection results subject to the future scenarios. Changes from the present time to the future indicate increased precipitation over southern and southeastern Brazil and areas nearby and the tropical western South American coast. Reduced precipitation is projected over eastern Amazonia, northern South America and southern Chile. The changes are related to changes in the low level wind flow over the tropical North Atlantic, which reduces the advection of moisture to the continent and also to the increased low level flow over central South America southwards, which increases the humidity in the southern regions. The upper level flow changes are also consistent with the precipitation changes. There is a weakening of the Bolivian High and a strengthening of the subtropical jet over the continent. The SACZ dipole pattern is well simulated and in the future projections the southern center anomalies are more intense than in the present time. The PSA1 and PSA2 patterns are well represented in the present climate, but in the future projection only one dominant mode is identified as the typical teleconnection over the Pacific and South America.
Highlights
The impacts of climate variability over South America have been analyzed using precipitation data derived from satellite and observations at the surface, atmospheric variables from reanalysis, Sea Surface Temperature (SST) from reconstructed datasets and results from numerical models simulations
The South Atlantic Convergence Zone (SACZ) and the Pacific South America (PSA) patterns are analyzed in simulations of present climate and in future climate projections
The PSA1 and PSA2 patterns are well represented in the present climate, but in the future projection only one dominant mode is identified as the typical teleconnection over the Pacific and South America
Summary
The impacts of climate variability over South America have been analyzed using precipitation data derived from satellite and observations at the surface, atmospheric variables from reanalysis, Sea Surface Temperature (SST) from reconstructed datasets and results from numerical models simulations. The cyclonic circulation at high levels, over southeastern South America, which contributes to the convection in the SACZ, is part of the PSA wave train pattern [9,10]. In the winter, this pattern can generate favorable conditions for the displacement and development of synoptic systems, such as frontal systems over South America [15]. [18] showed that this pattern is linked to the dipole precipitation with centers of action in the SACZ and in the Southeastern South America (SESA) region in CMIP3 model results. The simulation of the PSA pattern and its behavior in future projections is investigated
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