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.