Intraseasonal interactions between the tropics and extratropics in the Southern Hemisphere

Abstract

Enhanced convection over Indonesia is found to be associated with increases of both the southward component of the meridional divergent wind and of the westerly zonal wind to the south of the heating region during the SH summer. The increased westerly wind gradients, resulting to a certain extent from strengthened northerly flow, together with increased values of the southward component of the divergent wind, lead to an enhancement of the Rossby wave source in the vorticity equation in the vicinity of Australia. Streamfunction anomalies indicate that a wave train evolves from this region, following the typical ray path expected from linear theory. Tropical-extratropical connections are less pronounced during SH winter than during summer, though an increase of westerly winds in the SH is found associated with enhanced convective activity in the Northern Hemisphere. -from Authors