Hydrological cycle, temperature, and land surface−atmosphere interaction in the La Plata Basin during summer: response to climate change

The austral summer response (2071−2100 with respect to 1981−2010) in terms of precipitation, temperature, and evapotranspiration was analyzed over South America, with emphasis on the La Plata Basin (LPB), using an ensemble of regional climate models. Seasonal mean precipitation increased over the southern LPB, consistent with CMIP3 and CMIP5 ensembles. However, the region of wetting (in the sense of precipitation minus evapotranspiration) over the LPB shifts to the north and northwest, compared to the region of increased precipitation. The LPB is characterized as the South American region with the largest gradient in temperature change (maximum warming north of the LPB and lowest temperature rise near the Rio de la Plata). The interannual variability of evapotranspiration has a geographic distribution similar to that of temperature variability, with a maximum in northern Argentina, suggesting that the 2 variables are interrelated. In turn, in the current climate, the southern LPB is a transition zone in which the evapotranspiration regime depends on the availability of soil water. The model ensemble also points to a similar geographical distribution of limitation regimes (energy- vs. soil moisture-limited evapotranspiration) for present-day and future conditions over South America. In particular, the evapotranspiration regime is projected to continue to be soil moisture-limited over the LPB. Nevertheless, the coupling between land and temperature decreases in areas with increasing soil water availability. In the southern LPB, interannual variability in temperature and evapotranspiration tend to decrease, while rainfall variability exhibits the opposite behavior.