How Monsoons Work

July 25, 2015

Most people know what monsoon is, in the sense that, we’ve been told to avoid booking a holiday to Nepal, India or Southeast Asia when there’s a reasonable chance it’ll also be in town. But do you know why monsoons happen or why some people even rejoice at its arrival? Join GHT’s monsoon series, starting off with an interesting meteorologic journey for beginners.

The word monsoon is believed to come from the Arabic word “mausim” which means a shift in wind or season. While there are a couple different monsoon systems in the world, the Asian monsoon is the most prominent and dramatic in the world, affecting a large area of land from Nepal, India through Southeast Asia.

A monsoon is a seasonal change in the direction of the prevailing winds in a region. During most of the year, winds blow from land to ocean making the air dry. However, during certain months of the year (usually June-September), the winds begin to blow from ocean to land bringing with it moist air. These moisture-laden ocean winds are what causes monsoonal rains.

So what makes the prevailing winds change direction? This will happen when there is a difference in temperature between the ocean and continent.

The sun warms up landmass faster than large bodies of water. As the land heats up in late spring and early summer, it causes the air to rise and creates a large low pressure system close to the ground surface. The sun also warms the surrounding ocean waters, but at a much slower speed.

The cooler air above the oceans is moist and more dense creating a high pressure zone. Due to the pressure gradient, winds flow from high pressure areas to low pressure areas. The change in pressure, resulting from the change in temperature over land and ocean, causes the winds to change from land-to-ocean direction to an ocean-to-land direction.

While long and heavy seasonal rains may deter some travelers, there are certain benefits that come with the monsoon season. In countries like Nepal for instance, rice and tea farmers rely on the yearly rains to harvest healthy crops. For people in rural areas of Nepal the monsoon brings with it lively and colorful festivals, like the famous Ropain festival, to celebrate and pray for the timely arrival and departure of the rains.

Tune back in next week to find out why traveling to Nepal during monsoon season can be a great experience.

 

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