WORLD PATTERNS OF PRECIPITATION The pattern of rainfall in the world is very complex and only a very broad zonal pattern can be detected. Equatodal areas have the most precipitation due to high temperatures and consequent large moisture holding capacities of air, and also the presence of large oceanic water surfaces to supply the moisture. Most of the rainfall is convectional. Conversely, polar areas receive scanty rainfall because of low air temperatures.
Middle latitudes, between these two extremes, have a complicated distribution where high rainfall patterns relate particularly to the westerlies in both the hemispheres and also to their cyclone tracks. Regions of the lowest rains coincide with regions of subsiding air because of high pressure conditions. This occurs mainly in the sub tropics and on the eastern sides of the oceans (or western margins of continents), e.g., the Sahara desert. Rainfall pattern is greatly affected by the mountain ranges; for example, the Rockies and the southern Andes, where the windward sides record high rainfall, while the leeward sides are marked by rain-shadow areas. Altitude also plays an important role on the local scale. There is a general increase in precipitation with height up to about 2 km, while beyond this, precipitation diminishes due to the coolness of air.
All places having the same rainfall are represented on a map by lines called isohyets.
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment