The torque exerted on the atmosphere by the Southern Alps

Abstract

Abstract Monthly mean sea-level pr,essure data, averaged over the four-year period 1946–49, for 16 meteorological stations are used to calculate monthly mean values of the average zonal pressure gradient at mean sea level for 21 topographical sections across the South Island of New Zealand (at ¼-degree-latitude intervals) from 41° S to 46° S. These data are used to compute average monthly values of the torque (about the earth's axis of rotation) exerted on the atmosphere by pressure differentials across the South Island ranges (mainly the Southern Alps) for the ten ½-degree-latitude zones lying between 41° Sand 46° S. Tables showing computed pressure gradients and torques are presented, and the variation of these latter quantities with latitude and time of the year is discussed. It is shown that the torques due to the Southern Alps act mainly to abstract eastward absolute angular momentum from the atmosphere and that in this respect they are on the average about ten times as effective as surface friction ...