A Diagnostic Study of the Transition of the 30 hPa Circulation in Northern Spring

Based on the northern 30 hPa daily altitude and temperature data for 1965—1986 and monthly mean ozone observations for 1958—1976, studies are conducted on the natural transitional process of the circulation from winter to spring by means of dynamic approach and statistical diagnostic analysis. Results are obtained as follows: (1) the first day on which the E index of eddy variance of the height field in the polar-cap area north of 50 oN is smaller than 4×104 (dagpm) 2 can be taken as an approximate measure of the beginning of spring for the natural season; (2) the circulation in the period from late winter to early spring experiences significant changes in the pressure, temperature, and zonal-meridional wind fields; (3) stationary and transcient vortex momentum, heat flux and flux convergence (divergence) undergo remarkable temporal-spatial variations; (4) in both the early and late transitions into spring, the heat source—ozone in the polar stratosphere shows zonal, meridional and vertical anomalies