Regional climate simulations of the changes in the components of the moisture budget over South America

摘要

The moisture transport over South America (SA) was investigated through the vertically integrated moisture flux of three regions: the Amazon (AMZ), Northeastern Brazil (NEB) and the La Plata Basin (LPB), in different climates, past (1961-1990) and future (2071-2100), in the summer (DJF) and winter (JJA) seasons. For this, we used the results of the simulations of four regional climate models (RCMs) of the Regional Climate Change Assessment for the La Plata Basin (CLARIS-LPB) project. The capacity and limitations of the models to simulate seasonal precipitation for the past period is discussed. In general, the RCMs tended to overestimate the observed precipitation during DJF in the NEB and underestimate it during JJA in the LPB. In relation to change in precipitation (future minus past), the RCMs indicated a decrease in precipitation over northern SA. The average fluxes of the AMZ and NEB regions provided most of the water vapour through the east and north edges, which indicates that the contributions of the North and South Atlantic trade winds are equally important for the entry of moisture during JJA and DJF. This configuration was observed in all models and climates. By comparing past and future climates, the moisture flux convergence during the past was lower relative to the future in different regions and seasons, with statistically significant differences at the 5% level considering the Student's t-test. In the same study, we compared the simulated (RCMs) and reanalysis moisture flux (ERA-40) in the past climate. The result indicated that the CLARIS project's RCMs are capable of simulating values similar or equal to the observed ones, providing high quality data for SA that can be useful in the analysis of changes in future moisture fluxes.