Seasonal Variations in the Lower and Upper Atmosphere

Abstract

ALTHOUGH the main temporal variations in the ionosphere show a very large measure of solar control, it has long been recognized that some ionospheric phenomena have features which strongly suggest a non-solar origin or control. One such example is the ‘winter anomaly’ in ionospheric absorption. Thus a recent survey¹ snows that this phenomenon seems to have a definite regional character in that although on any one day it may extend over areas of at least 10⁶ km² its enhancement in one longitude zone appeared to correspond to a diminution in its intensity in another longitude zone. Recently there has been clear evidence that at least part of this ‘winter anomaly’ is to be associated with abnormal warmings in the stratosphere at levels of about 30 km. Convincing evidence for such a relationship has been found in some recent work by Shapley and Beynon at Aberystwyth (preceding communication). As part of a broader consideration of this problem we have examined the seasonal variation in various parameters at different levels in the atmosphere and these are briefly reported below.