Mountains

Abstract

The jet stream hits the Rocky Mountains and is strongly affected by them. Arguments of fluid dynamics show how a semi-permanent anticyclone is formed over the mountains, and then a stationary Rossby wave train follows downstream. This extends across North America and beyond, with profound consequences for regional climate, for example allowing frequent surges of cold, Arctic air down over eastern North America. A brief discussion also considers how the jet stream may have differed in climates of the distant past.