An atmospheric climatology of the southern hemisphere based on ten years of daily numerical analyses (1972-82): II Standing wave climatology

Abstract

A standing wave climatology for the southern hemisphere has been prepared from ten years of daily hemispheric numerical analyses from the World Meteorological Centre, Melbourne for the period September 1972 till August 1982. Standing wave diagnostics of the geopotential height, wind and temperature on seven pressure lev-els are presented for summer and winter. These are compared to those from the earlier southern hemisphere climatology of Taljaard et al. (1969) and to the standing waves in the northern hemisphere.In general, the standing waves in the southern hemisphere have large zonal and short meridional length scales and an equivalent barotropic vertical structure. There is very little variation of the standing wave amplitude with season. At high latitudes, there is a westward phase tilt of the standing waves with height, indicating upward propagating waves. The results suggest that thermal and orographic forcing associated with Antarctica are the major forcing of standing waves in the southern hemisphere. In the subtropics, there is a shorter zonal length scale and a phase reversal of the standing waves between summer and winter, indicating the influence of continent-ocean temperature contrasts.The major differences from the earlier southern hemisphere climatology are the larger amplitude temperature standing wave and the greater importance of smaller scales in middle and high latitudes. The different analysis systems used for the two climetologies have led to some differences in the standing wave results.