Global time and space changes of satellite radiances received from the stratosphere and lower mesosphere

Abstract

Satellite-measured radiances make it possible to investigate the temperatures in the stratosphere and lower mesosphere on a global scale. The annual progression of radiances received with channels A and B of the selective chopper radiometer is discussed, emphasis being on the differences between the northern and southern winters. Major midwinter warmings, leading to a breakdown of the stratospheric circulation, took place only in the northern hemisphere, where in turn they were followed by a second cooling in late winter. In the upper south polar stratosphere and lower mesosphere, the minimum of radiances was reached in early winter. A steady warming began immediately after this minimum and led to a reversed meridional temperature gradient (final warming) about two months earlier than over the arctic. Because of this difference, the upper stratosphere and lower mesosphere over the antarctic were as warm as or warmer than those of the arctic outside the period of the northern midwinter warming. Midwinter radiance changes over both polar regions are coupled with changes of opposite sign in the subtropics and tropics of both hemispheres; the occurrence of the annual temperature maximum in the upper tropical stratosphere and lower mesosphere in January and February is probably linked with the winter circulation in the northern hemisphere.