Why is it rainy in september
This is The Answer
Why does it rain between June to September, generally, every year in India? Why is it so permanent that we call these 4 months the rainy season?
Why does it rain between June to September, generally, every year in India?
I hope you are aware why summer and winter happens. In short, starting from March, the northern hemisphere is inclined towards the sun. This causes summer season.
We have a desert region called Thar to the northwest of India. Temperatures here exceed 45 degrees in summer. This heat builds up and eventually creates a low pressure area over here. This low pressure area isn't localised, its a very broad one.
At the same time, a high pressure system forms over the southern Indian Ocean.
Its standard physics that air moves from high pressure area to low pressure area to fill the gap. The air moves from the high pressure system over south Indian Ocean to the low pressure area over That desert.
The reason for changes in seasons is the apparent movement of SUN from the Tropic of Cancer (Lat 22.5 Deg N) (June 22) to Tropic of Capricorn (Lat 22.5 Deg S) ( Dec 22) in six months and its return in another six months. The diurnal variation of temperature over land is very high but the Oceans mix by turbulence and up to a depth of 200 meters the temperature is nearly the same. They are reservoirs of solar energy. Average temperature of the Arabian sea and the Bay is much higher during these months than during the next 6 months that follow. The thermal lag is 30 to 35 days. Oceans transfer the excess energy to the atmosphere. At all temperatures water that evaporates absorbs heat and the heat is released to the atmosphere when it rains. In a “Super cyclone” the top layers (30,000 Ft) near the “Eye” can warm up by 5 Deg C! From June to September monsoon rains transfer heat to the atmosphere in the form of rains.
Why is it so permanent?
It is permanent because this weather pattern adheres to the coordination of earth and sun, which is permanent.