A DIAGNOSIS OF THE DEVELOPMENT OF A WINTER ANTICYCLONE OVER NORTH-AMERICA

This paper examines the 48-h life cycle of a winter anticyclone occurr ing over North America from 18 to 20 January 1979 using Goddard Labora tory for Atmospheres FGGE level IIIb (SOP 1) global analyses on a 4 de grees latitude by 5 degrees longitude grid. Applying the relatively ne w methodology of the Zwack-Okossi equation, results show that anticycl onic vorticity advection and cold-air advection acted to develop the a nticyclone, while adiabatic warming in the descending air opposed deve lopment. Other forcing processes made only small contributions to anti cyclone changes. Vertical profiles of the development quantities revea l that vorticity and temperature advections, as well as the adiabatic warming, maximized in the 200-300-mb layer.