It’s officially the rainy season! And that means lots of grey clouds, rain that feels endless, and very green surroundings. But have you ever wondered why we in India experience the monsoons, while other countries like the UK or US don’t have a dedicated season of rain?
India falls in a tropical zone, which is the area surrounding the equator. This area is defined by the Tropic of Cancer in the northern hemisphere and the Tropic of Capricorn in the southern. The tropics are characterised by a climate that is hot, sunny, humid, and rainy. The weather conditions divide the tropical climate into two major parts – wet and dry seasons. The wet season typically begins around April and goes on till September. These months see an increase in temperatures and rains. Remember all those summer showers? Those happen because we’re in a tropical climate.
However, we must note that not all regions in the tropical belt have the same kind of climate or receive the same amount of rainfall. The tropical climate is just the setting for the monsoons, but what really influences it is the water bodies around a particular area and wind patterns around it.
Rains, as we all know, depend on the bodies of water they come from. The space where the Indian Ocean and the Pacific Ocean meet makes for the most ideal monsoon conditions, as it falls in the section of the Earth that receives the most amount of direct sunlight. This is why south-east Asian countries like India, Pakistan, Japan, and Korea, and parts of Australia have monsoons.
Winds are the actual driving force behind the monsoons. The air on Earth tends to move in set patterns, and the air in the tropics moves in a pattern called the Hadley Circulation (Named after 18th-century lawyer and meteorologist George Hadley). When the sun heats up the water around the equator, warm, moisture-laden air rises about 10-15 km above the surface and flows towards the poles. It then descends towards the Earth’s surface around the subtropics, which cover Southeast Asia, Australia and parts of South America, and makes its way back to the equator, forming a cyclic pattern.
When the warm air blows towards the poles, it creates areas of low pressure around the equator, which is then again filled with the moisture-laden winds coming back from the poles. It is these winds that bring the monsoon clouds, making it rain around the equator, thus completing the Hadley Circulation. This area, where warm air rises and condenses, forming clouds, is called the Intertropical Convergence Zone (ITCZ) and it can be seen from space as a bunch of clouds on the surface of the Earth. The Hadley Circulation doesn’t remain in the same place every year and tends to shift, thus making weather predictions complicated every year.
The Hadley Circulation is not the only factor affecting wind patterns and the rains, however. The Earth itself is a major influence on how and when we get rains, because of its rotations. Due to the Earth’s rotation, the winds blowing from the south and north poles towards the equator are then shifted slightly – towards the west in the northern hemisphere and towards the east in the southern. These winds then become ‘trade winds’, which were highly vital for seafaring traders in the olden days and hence were named as such. The Easterlies (winds that blow toward the east) and Westerlies (winds blowing toward the west) are trade winds that bring the monsoons to India and its neighbouring countries.
Another reason the monsoons are so strong in India is the Himalayas. The large mountain range blocks dry, cold winds from the north. This creates an enclosed space for the trade winds to come into the subcontinent and stay there, thus making it rain all over the country. This is also why other countries don’t face such strong monsoons, as their geography may not support it.
Of course, climate change has now become a major influence on wind and rain patterns. We are experiencing an increase in unseasonal rains and the amount of rain we receive every year is fluctuating a lot more. Winds and ocean currents are also affected by this as the Earth is heating up, thus changing when the monsoons arrive and how long they last.
What do you think the future of India’s monsoons looks like? Let us know your thoughts in the comments below.
Uncover other mysteries of the weather in ‘Did You Know?’:
1. Why does the monsoon happen?
Water vapor from the Indian and Pacific Ocean condenses as air rises and cools at the Equator, forming clouds and falling as rain in the tropical regions around the equator.
2. Why does India have a tropical monsoon type of climate?
India has a tropical monsoon climate due to being close to the equator, which brings a lot of rain to the subcontinent. Additionally, the Himalayas block any cold winds coming from the north, thus sealing the tropical weather in.
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