Equatorial counter electrojets and polar stratospheric sudden warmings - a classical example of high latitude-low latitude coupling

Abstract

Favored occurrences of Equatorial Counter Electrojets (CEJs) with a quasi 16-day periodicity over Trivandrum (8.5° N, 76.5° E, 0.5° N diplat.) in association with the polar Stratospheric Sudden Warming (SSW) events are presented. It is observed that, the stratospheric temperature at ˜30 km over Trivandrum shows a sudden cooling prior to the SSWs and the CEJs of maximum intensity which occurs around this time. In general stronger CEJs are associated with more intense SSW events. The stratospheric zonal mean zonal wind over Trivandrum also exhibits a distinctly different pattern during the SSW period. These circulation changes are proposed to be conducive for the upward propagation of the lower atmospheric waves over the equatorial latitudes. The interaction of such waves with the tidal components at the upper mesosphere and its subsequent modification are suggested to be responsible for the occurrence of CEJs having planetary wave periods.