A Diagnosis of the development of a Winter Anticyclone over North America

Abstract

This paper examines the 48-h life cycle of a winter anticyclone occurring over North America from 18 to 20 January 1979 using Goddard Laboratory for Atmospheres FGGE level IIIb (SOP 1) global analyses on a 4° latitude by 5° longitude grid. Applying the relatively new methodology of the Zwack-Okossi equation, results show that anticyclonic vorticity advection and cold-air advection acted to develop the anticyclone, while adiabatic warming in the descending air opposed development. Other forcing processes made only small contributions to anticyclone changes. Vertical profiles of the development quantities reveal that vorticity and temperature advections, as well as the adiabatic warming, maximized in the 200- 300-mb layer.