A Climatology Study of the South Atlantic Subtropical High Daily Variability During the Austral Winter

An automated procedure for finding and tracking high pressure centers has been applied for 15 years period (1982-1996) for pressure reduced to mean sea level dataset from the NCEP Reanalysis during june-july-august months to investigate the behavior of the South Atlantic Subtropical High (SASH). The area of interest extends from 0 to 50ºS latitude and 10ºE to 80ºW longitude. The climatology for the latitudinal and longitudinal variations of the high-pressure center during the winter is constructed. Whereas the major longitudinal displacements and the positions more westward (around 10ºW) are found in July, the center is located more eastward (around 5ºW) in the other months. Its daily variation presents a periodic behavior similar to frontal systems.

Surface pressure fields indicate that the SASH is continuously fed by extratropical anticyclones formed over the South American continent. On the other hand, frontal systems tend to weakening their structure. Moreover, the vertical analysis confirmed the direct contribution from Hadley cell in the maintenance of the anticyclone. Isentropic potencial vorticity (IPV) and wind at the 310 K isentropic surface showed that air masses from upper troposphere descend in the east side of the SASH and are incorporated into its structure.