Recent Changes in the Annual Mean Regional Hadley Circulation and Their Impacts on South America

摘要

This work employs the regional climate model RegCM4 and observational datasets to investigate the impacts of changes in the intensity and poleward edge of regional HC over South America (HCSA) on the patterns of wind, geopotential height, precipitation, and temperature during the period 1996-2011. Significant trends of HCSA intensification and poleward expansion are found during the period analyzed. To evaluate the effects of these changes over SA, two composites, representing the intensification and poleward expansion cases, are examined separately. Significant correlations are seen between the temperature, zonal wind, and the HCSA intensity over the northern, central, and southern regions of SA and South Atlantic. Results show that, in both composites, regions with anomalous easterly (westerly) winds coming from (towards) the Atlantic Ocean have negative (positive) correlations with the HCSA intensity and poleward edge. The model performance varies regionally and the southern SA region exhibits better agreement with the observations. The role of the sea surface temperatures in driving the changes in the HCSA is examined. Notable similarity is found in the results for the two cases analyzed, which could indicate that, in most cases, the changes in the intensity and poleward edge of the HCSA are occurring simultaneously.