ABSTRACT
Although this book is concerned with the weather and climates which are a vital part of the human environment at the ground, it is necessary to pay some attention to the stratosphere. This is partly because of the likelihood of (a) some interaction between the independently generated circulations of the stratosphere and troposphere, and (b) variable damping effects upon the circulation in the lower atmosphere (troposphere) due to some (probably slight) variation of long-term mean tropopause height associated with variations in the direct heating of the stratosphere. But also there is reason to suppose that some grand-scale effects of the circulation and patterns of vertical motion in the troposphere may reveal themselves in simpler shape in the lowest layers of the stratosphere that are affected by that vertical motion. The technical difficulty of developing adequate observational coverage, particularly the difficulty of developing balloons capable of carrying instruments regularly to heights of 30 km and above in the coldest climates on Earth, has meant that daily surveys of the stratospheric circulation over any large part of the northern hemisphere began only in the early 1950s and have — all too sparsely — covered the whole world still more recently. Observations in the stratosphere above 30–35 km mainly depend on rocket firings, made regularly only since 1959 and more or less limited to North America though now being made — at least from time to time — in many other areas: e.g. the Hebrides, the equatorial Indian Ocean and Antarctica. So research on possible ‘coupling’ between the tropospheric and stratospheric circulations is as yet in its infancy. On many aspects only tentative interpretations can be put forward so far; and, particularly in connexion with the longer-term anomalies and changes of climate, we can speak only of probabilities and what may reasonably be supposed from physical principles and the relevant phenomena so far observed.
