A Study of the Mountain Torque and its Interannual Variations in the Northern Hemisphere

Abstract

Abstract Values of the large-scale mountain torque between 10S and 80N are computed for each month of the five-year period, May 1958 through April 1963. A careful comparison with earlier midseason values presented by Newton using different data sources and different analysis techniques is made. The calculations appear to be equally sensitive to differences in smoothing of the mountain profiles as to differences in basic geopotential height data used. Interannual variations in the monthly-mean mountain torques are found to be large, especially during the winter half-year. In general, the large-scale mountain torque gives only a minor contribution to the total surface torque as estimated by other investigators. However, when integrated over the Northern Hemisphere as a whole, the mountain and frictional torques appear to be equally important. Both torques seem to act as a sink of angular momentum in summer and a source in winter.