For two years running, Kerala, one of India’s southernmost states, has seen record floods throughout the months of July and August that have cost untold billions in damage and have taken countless lives. This wanton destruction is the result of a yearly weather pattern that switches between a hot, dry climate to torrential downpours, known as the monsoon.
The monsoon is caused by a seasonal reversal in wind direction and occurs primarily in Africa, Central America, Australia, and of course, South Asia. As you may know, winds are caused by the uneven heating of the Earth’s surface. The disparity in temperature between two different areas will result in a pressure difference as well, with the hotter area experiencing low pressure and the cooler area experiencing high pressure – the wind then flows from the area of high pressure to the area of low pressure. The aforementioned areas are all very close to the ocean, and because land heats and cools much more quickly than water does, the pressure is different above these two areas and the winds of the monsoon will flow, and the wind will change direction when the land becomes warmer or cooler than the nearby ocean, causing the pressure, and therefore the wind direction, to change.
During the warmer months of the year, the land will grow significantly warmer than the ocean, and because the ocean has much greater pressure, an ocean-to-land sea breeze will form and bring much rain to the land area, causing the torrential downpour discussed earlier. In fact, according to NOAA, about 75% of India’s annual rainfall is brought by the summer monsoon. As the months pass by and the land begins to cool, there is a gradual transition into the dry, or winter, monsoon as the land starts to grow cooler than the ocean. Once said transition is complete, the wind reverses direction and begins to blow from the land to the ocean. The dry monsoon is much less well-known and is less powerful to boot – the pressure gradient forces carrying the wind from the high-pressure land to the low-pressure sea are simply not as strong.
While it may seem that monsoons always are bad news, that isn’t actually always the case, only during instances of heavy monsoons like 2018 and 2019. In fact, much of India’s agriculture relies on the wet monsoon coming in a timely manner, and without it, their water supplies for the year may be diminished. However, these two episodes of great flooding in Kerala have rocked the state like a one-two punch, and the people of the area are reeling. Last year, I myself went to Kerala just before the monsoons started and the rain was relentless beyond anything I had ever seen, going on for days at a time, never ending. Life essentially was at a standstill, and although my own hometown, due to its high elevation, was relatively unharmed, the surrounding areas were hit with numerous landslides and deluges. With that, I should mention that the Chief Minister of Kerala has set up a relief fund for the recovery of the state – I encourage you all to donate, and if you can’t I hope you can spread the word about this ongoing crisis.