Spring-warming transfer processes in the lower antarctic stratosphere

Abstract

Earlier evaluations of heat balance requirements in the lower stratosphere from sounding data had resulted in excessive radiational net-cooling rates (budget residuals) during 1958 and 1960 spring warming periods, viz. 4° to 6°C/day. The imbalance arises chiefly from stratospheric subsidence rates calculated with the assumption of vanishing net mass transport across the top of the highest datum layer (75 and 25 mb level respectively). When vertical mass transport is assumed to vanish relative to a minimum temperature surface (stratobase) which descends on to the principal Antarctic tropopause, quasi-Lagrangian radiational cooling rates of 0.5 to 1.5°C/day obtain in 1960 and 1964 stratospheric warming periods.

The hypothesis of an impermeable stratobase requires transient ascent at the 25 mb level suggesting a temporarily reversed meridional circulation overlying the direct polar cell. The associated vertical divergence in the lower stratosphere is examined for its effects on ozone changes in this layer and observed changes of total ozone at Halley Bay, Mirny and Dumont d'Urville.