On the Influence of the Earth’s Orography on the General Character of the Westerlies

The upper westerlies in middle latitudes possess, in the mean, a wave-like character which has been explained as a result of thermal contrasts between land and sea. On the other hand, recent theoretical investigations by QUENEY, CHARNEY and ELIASSEN have shown that an obstacle of the dimensions of the Rocky Mountains generates a wave pattern downstream whose scale is comparable to the observed mean waves. In the present paper these theoretical studies are extended, and an attempt is made to discuss, in a general way, the influence of the northern hemisphere mountains on the character of the westerlies. Finally the paper points out some of the climatic consequences of the proposed dynamic-topographic control of the prevailing flow patterns.