Upper-Atmospheric Sodium and Stratospheric Warmings at High Latitudes

Abstract

A cross correlation (by the superposed-epoch method) has been carried out between sodium abundance, measured in twilight at Saskatoon, and stratospheric warmings, observed in temperature data at Churchill and Alert. A significant peak appears to be present in data from four winters. It is suggested that vertical motion, as indicated by the warming events, is raising a source of sodium atoms into the 90-km region. This source is probably in the form of dust (or aerosol) particles, whose origin could he either meteoric or marine. Partial evaporation of these particles in the daytime could explain the additional sodium observed in the dayglow. A natural explanation is also given of the seasonal abundance variation and the very steep sodium distributions often observed.