What causes the monsoon and what parts of the world experience monsoon climates?
Rainy days and Mondays get me down. Into each life some rain
must fall. Rain, rain go away come again some other day. In much of the world, especially North America and Europe, rain and clouds are synonymous with feeling melancholy or gloomy. However, for about half the world, rain is considered the breath of life. Most of central Africa, northern Australia, southern and eastern China, Japan, Malaysia, Indonesia, southeast Asia, Pakistan, Bangladesh and India are influenced by and dependent on rain bearing seasonal winds. In these places, the coming of the wet season brings tears of joy, laughter and good tidings. What makes the rains so welcomed is that preceeding their arrival, conditions are often extremely harsh. In India, the land is barren, dust storms blot out the horizon and temperatures are routinely over 100 degrees F (38 C).
The word monsoon comes from the Arabic word mausim, which means season. The monsoon is a season of winds. It's changing wind patterns that usher in the rainy weather we associate with the monsoons. Usually, from about mid May through September, winds from the southwest bring heavy rains to much of southern Asia. During the colder months, these winds reverse direction and bring in cool, dry air. When this happens, places having northern or northeast coastlines, like Australia, New Guinea and Borneo, get their wet season.
Monsoon conditions are set up when the hot air which builds up over land areas forms a 'thermal low'. As the heated air lifts, air from surrounding areas is sucked in to replace it. When land massses have been heated for long periods of time, relatively cooler air from over ocean areas is ushered in. It's this moisture-laden air that drenches the parched land and abruptly ends the dry season. In a National Geographic article on monsoons, Pritt Visalind describes the monsoon as Asia breathing in than breathing out. The inhalation is the summer monsoon (rainy season) and the exhalation is the winter (dry season) monsoon.
Although the monsoon rains always seem to come, it's hard to know exactly when they will arrive. In India, one of the first signs that the monsoon rains are on the way is the appearance of large ocean swells from the southeast. Strong winds are driving these swells, and eventually the winds and the clouds they carry will reach the Indian subcontinent. The Indian poet Kalidasa wrote that "The clouds advance like elephants, enormous and full of rain. They come forward as Kings among tumultuous armies; their flag is lightning, the thunder is their drum..."
The monsoon rain can be as relentless as the drought which preceeds it. It can rain every day for weeks. These are typically not gentle rains or brief showers, but rather frog strangling downpours. Bombay,
India receives about 88 inches (224 cm) of rain each year, nearly all of it between May and September (almost three times as much rain as Chicago gets). When the wet winds reach the flanks of the Himalayas,
prodigious amounts of rain are released as the moist air is forced against the mountains. The village of Cherrapungi in northern India
endures perhaps the highest average yearly rainfall on Earth, 450 inches (1150 cm).
It's not only the areas around the Indian Ocean that are subjected to monsoons. Many places in the world have distinct wet and dry seasons associated with changing wind patterns. In fact, parts of Texas (along the Gulf of Mexico) and southern Arizona experience monsoon conditions. Tuscon, Arizona gets more than half of its annual rainfall during the
hot summer months when relatively moist southeast winds from the Gulf of Mexico are pulled in as a result of a thermal low that develops over Arizona and parts of southern California and New Mexico.
What causes the monsoon and what parts of the world experience monsoon climates?
5/17/96