Convective Winds
Convective winds originate from small-scale pressure gradients produced by local temperature differences. Air made buoyant by warming at the surface is forced aloft; air which is cooled tends to sink. Convective winds may be strengthened, weakened, or eliminated by general winds. The influence of these general winds on the convective wind systems varies with the strength of the general wind, its direction relative to the convective circulation, and the stability of the lower atmosphere.
The nature and strength of convective winds vary with many other factors. Since they are temperature-dependent, all features of the environment that affect heating and cooling are significant. Among the more important are season, diurnal changes, cloud cover, nature of the terrain and its cover such as water, vegetation, or bare ground, and the moisture and temperature structure of the overlying atmosphere.
The most familiar convective winds are land and sea breezes, valley and slope winds, whirlwinds, and winds associated with convective cumulus and thunderstorm clouds. In the land- and sea-breeze system, the local winds are due to land-water temperature differences, which, in turn, produce differences in the temperature of the overlying air. Slope winds are due to temperature differences between slope air and air over the valley. Valley winds likewise result from temperature differences between valley air and air at the same elevation over the plains. Strong local heating will develop a very unstable layer of air near the surface, and the sudden release of this concentrated energy, usually following a triggering action, may produce whirlwinds. Thermal updrafts resulting from local heating may produce cumulus clouds, which, under suitable moisture and instability conditions, may develop into thunderstorms. Updrafts are convective winds characteristic of developing cumulus clouds, but downdrafts are produced in thunderstorms after precipitation begins falling from the cloud.
Encyclopedia ID: p360
