A Comparison of Observed and Simulated Properties of Sudden Stratospheric Warmings

Abstract

Significant advances have been made recently both in observational studies and in dynamical numerical simulations of stratosphere warmings. Observed characteristics of warmings are reviewed, with discussion of the trajectory of warm cells, the vertical and horizontal scale of the warm-air systems, the time-scale of warming, circulation effects, initial zonal flow conditions before a warming, and details of the energy budget before and after warming. Distinctions are drawn between the 1973 and 1963 types of warmings, which involved a poleward advance of warm air in wave 1 and wave 2, respectively. In contrast to the warming of 1963, a strong baroclinic conversion of eddy potential to eddy kinetic energy was not discerned in 1973, but both events were preceded by extraordinarily large fluxes from the troposphere. The results of dynamical warming simulations by several investigators reflect varying degrees of success in reproducing observed features of warmings. The results of Matsuno and Newson closely resemble important features of the 1963 and 1973 warmings, respectively. Some areas of apparent disagreement are explainable in part by the difficulty of matching the phase of simulated and observed events in time and space. Factors requiring elucidation include the physical process accounting for upward energy fluxes leading to warmings, the role of wave interaction in the stratosphere, and the associated tropospheric synoptic conditions.