Atmosphere Contents

5. General Circulation

Rossby waves occur in mid latitudes

Not all of the surface air moves towards the equator. Some air moves towards the poles and deflects toward the east, resulting in a more or less westerly air flow, called the westerlies in both hemispheres. However, this general westerly flow is more variable than the trade winds of the low-latitudes as it is affected near the ground by cells of low and high pressure which travel east, associated with large scale waves called Rossby waves occurring in the upper troposphere. Greater coverage by land masses in the northern hemisphere also obscures the westerlies by the influence of surface temperature changes and presence of mountain ranges. The westerlies are more marked in the southern hemisphere as the oceans do not allow the formation of pressure cells.

Mid-Latitude Rossby Wave

What are Rossby waves?