ANGULAR MOMENTUM AS A PARAMETER IN THE INVESTIGATION OF CYCLONE-SCALE CIRCULATIONS

Abstract

Angular momentum relative to a fixed vertical axis is used as a measure of rotational flow on the scale of cyclones and anticyclones. An exact equation derived by Starr for the time rate of change of this momentum is expressed in an approximate form, and a long-period observational study is made in two regions to determine the validity and prognostic implications of the resulting relationship. It is found that the fluctuations of angular momentum can be accounted for primarily by a single effect?the horizontal transport of momentum across the boundaries of the regions. Moreover, a sufficient lag relationship is found to exist so that the transport serves as a predictor of the 12-hour change of momentum.