A Diagnostic Study of the Potential Vorticity in a Warm Blocking Anticyclone

Abstract

Dynamical features of the warm blocking anticyclone which persisted over Europe during the summer of 1976 are studied using National Meteorological Centre analyses. The dynamics am presented from the perspective of quasi-geostrophic potential vorticity q. The block is shown to be a region of anomalously low, almost uniform q?. Computed balances in the 300 mb monthly mean quasi-geostrophic potential vorticity equation show that the mean flow advection v???q? and the eddy forciv???q? of q? are of comparable magnitude and have the tendency to balance one another. It is suggested that transfer by synoptic scale systems acts to maintain the q? anomaly against its advection downstream.