Fun Learning - What is a Monsoon?

(Image courtesy: www.reckontalk.com)


The very mention of the word summer instantly brings to mind the term – ‘Monsoon’. But do you what the term refers to and where did the word originate?


The word Monsoon has been derived from mauism, the Arabic word for "season".

A monsoon often refers to a rainy season -- but this only describes the weather a monsoon brings, not what a monsoon is.

A monsoon is actually ‘a seasonal shift in wind direction and pressure distribution’ that causes a change in precipitation.

Although the word monsoon is usually used to refer to torrential rain, it actually describes the rains and the winds that bring them, as well as the corresponding dry season that follows.

Monsoons are most often associated with the Indian Ocean.

Southern Asia, especially India, experiences monsoons every summer. From June to September, a high-pressure system sits over the Indian Ocean while a low-pressure system sits over Asia. These systems bring torrential rains to southern Asia during this time.

Farmers rely on these rains for their crops to grow.

About 90% of annual rainfall falls during this time.

India and Southeast Asia depend on the summer monsoon. Agriculture, for example, relies on the yearly rain. Many areas in these countries do not have large irrigation systems surrounding lakes, rivers, or snow-melt areas. Aquifers, or supplies of underground water, are shallow. The summer monsoon fills wells and aquifers for the rest of the year.

Rice and tea are some crops that rely on the summer monsoon. Dairy farms, which help make India the largest milk producer in the world, also depend on the monsoon rains to keep cows healthy and well-fed.

How it works?

All winds blow as a result of pressure imbalances between two locations. In the case of monsoons, this pressure imbalance is created when temperatures across vast landmasses such as India and Asia, are significantly warmer or cooler than those over neighboring oceans. Once the temperature conditions on the land and oceans change the resultant pressure changes cause the winds to change.

These temperature imbalances happen because oceans and land absorb heat in different ways: bodies of water are slower to heat up and cool down, while land both heats and cools quickly.

During the summer months, sunlight heats the surfaces of both lands and oceans, but land temperatures rise more quickly due to a lower heat capacity.

As the land's surface becomes warmer, the air above it expands and an area of low pressure develops. Meanwhile, the ocean remains at a lower temperature than the land and so the air above it retains a higher pressure. Since winds flow from areas of low to high pressure (due to the pressure gradient force), this deficit in pressure over the continent causes winds to blow in an ocean-to-land circulation (a sea breeze). As winds blow from the ocean to the land, moist air is brought inland. This is why summer monsoons cause so much rain.

Some more facts about Monsoon

Monsoons always blow from cold to warm regions. The summer monsoon and the winter monsoon determine the climate for most of India and Southeast Asia.

During the winter the systems reverse, bringing particularly-dry weather for several months. About half of the world’s population lives in areas affected by the Asian monsoons.

Monsoons happen in other places around the world, too. These other monsoons, though, tend to be much smaller in scope.

Other areas that experience annual monsoons include areas of Africa near the equator, northern Australia, and even the southwestern United States, particularly Arizona.

As winter ends, warm, moist air from the southwest Indian Ocean blows toward countries like India, Sri Lanka, Bangladesh, and Myanmar.

The history of Monsoon Studies

The earliest explanation for monsoon development came in 1686 from the English astronomer and mathematician Edmond Halley. Halley conceived the idea that differential heating of land and ocean caused these giant sea-breeze circulations. As with all scientific theories, these ideas have been expanded upon.

Do Monsoons fail?

Monsoon seasons can actually fail, bringing intense drought and famines to many parts of the world. From 1876-1879, India experienced such a monsoon failure.

To study these droughts, the Indian Meteorological Service (IMS) was created.

(Source: wonderopolis.org; .nationalgeographic; weather.about.com, etc)