Some Synoptic Indices of the Southern Hemisphere Mean Sea Level Circulation 1972–77

Abstract

A set of 10 synoptic indices for the Southern Hemisphere is presented based on the first five years of numerical analysis by the Australian Bureau of Meteorology. The indices describe the characteristics and variability of the monthly and seasonal mean patterns obtained by the time averaging of the daily analyses, referring specifically to (i) the extension of the subtropical anticyclones to higher and lower latitudes, the latitude of the axis of highest pressure, the location of the anticyclonic centers and their longitudinal separation; (ii) the strength and variability of the midlatitude zonal westerlies; (iii) the latitude of the sub-Antarctic trough and the longitudinal spacing of its pressure minima; and (iv) the location of the Antarctic quasi-anticyclone. The indices are intended for maintenance as a historical series. They may provide a medium for monitoring the monthly and seasonal circulation of the hemisphere, for investigating its anomalies, and for validating numerical simulations of its gross features.