Weather Influences in the British Isles

Abstract

THE sun is the only source of terrestrial weather in the sense that the difference between the amount of solar radiation received in different latitudes is the driving force of the atmospheric circulation. The complexity of the earth's surface combined with its rotation about an axis introduces corresponding complexities into this circulation, but H. H. Clayton considers that “if there were no variation in solar radiation the atmospheric motions- would establish a stable system with exchanges of air between equator and pole and between ocean and land, in which the only variations would be daily and annual changes set in operation by the relative motions of earth and sun; the existing changes we call weather have their origin chiefly, if not entirely, in the variation of solar radiation.” It has been found that some parts of the earth, especially the tropics, respond readily to these solar variations, while in other parts the solar variation is almost completely masked by secondary modifications. Hence we may classify weather influences into two classes: solar, in which the influence of solar variation is directly recognisable, and terrestrial, depending on causes which at first sight are entirely due to the influence of the land, sea, or atmosphere. These two classes shade into each other, with no definite line between them.