2 minute read

Monsoon

When The Monsoon Fails

The importance of monsoons is demonstrated by the experience of the Sahel, a band of land on the southern fringe of the Sahara Desert. This area would also be arid if it were not for the seasonal monsoon, whose rains normally transform it to a grassland suitable for grazing livestock. The wetter southern Sahel can support agriculture, and many residents migrated to the area during the years of strong monsoons. Beginning in the late sixties, however, the annual monsoons began to fail. The pasture areas in the northern Sahel dried up, forcing nomadic herders and their livestock southward in search of pasture and water. The monsoon rains did not return until 1974. In the intervening six years, the area suffered devastating famines and loss of life, both human and animal, and placed extreme stress on the countries of central Africa.

Because of their tremendous effect on many tropical areas, atmospheric scientists continue to study the formation and variability of monsoons. Monsoon variations are still not entirely understood, making the prediction of the monsoon a distant goal. However, researchers have shown that monsoons are affected by El Niño, the changes in winds and sea water that occur in the tropical Pacific Ocean. Research continues into modeling monsoon circulations with complicated computer simulations.

Resources

Books

Frater, Alexander. Chasing the Monsoon. New York: Alfred A. Knopf, 1991.

McCurry, Steve. Monsoon. New York: Thames and Hudson, 1984.

Navarra, John G. Atmosphere, Weather and Climate. Philadelphia: W.B. Saunders Co., 1979.

Periodicals

Meehi, Gerald A. "Coupled Land-ocean-atmosphere Processes and South Asian Monsoon Variability." Science (October 14, 1994): 263.


James Marti

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Circulation cell

—A circular path of air, in which warm air rises from the surface, moves to cooler areas, sinks back down to the surface, then moves back to near where it began. The air circulation sets up prevailing (constant) winds at the surface and aloft.

Convection

—The rising of warm air from the surface of the Earth.

Heat capacity

—The amount of heat required to raise the temperature of a substance; water has a high heat capacity, while land surfaces (soil, rock, etc.) and air have much lower heat capacities.

Jet stream

—High speed winds that circulate around the Earth at altitudes of 7–12 mi (12–20 km) and affect weather patterns at the surface. Two important jet streams are the subtropical jet, flowing from west to east, and the weaker tropical jet, which flows from east to west.

Monsoon

—A seasonal change in the direction of the prevailing wind, often associated with a rainy or a dry season.

Subtropics

—Regions between 23.5 and about 35 degrees latitude, in both the northern and southern hemispheres, which surround the tropics.

Tropics

—The region around Earth's equator spanning 23.5° north latitude to 23.5° south latitude.

Additional topics

Science EncyclopediaScience & Philosophy: Molecular distillation to My station and its duties:Monsoon - General Monsoon Circulation, The Asian Monsoons, The Monsoon Of India, The Monsoons Of South China And Japan