QUES . Why do we have fewer cyclones in the Arabian Sea than in the Bay of Bengal? UPSC IES/ISS Exam 2023 General Studies . 200 words . 5 marks

HINTS:

Bay of Bengal is one of the most cyclone prone areas in the world. Interestingly such large numbers of devastating cyclones do not occur in the Arabian Sea on the other side of India. Generally, India gets 5 cyclones on an average in a year – four in the Bay of Bengal and one in the Arabian Sea.

Moreover cyclones of Bay of Bengal are stronger and deadlier also. According to the National Cyclone Risk Mitigation Project (NCRMP) data, around 58 per cent of the cyclones formed in the Bay of Bengal make landfall on the eastern coast. Whereas, the percentage is as low as 25 per cent in the case of the Arabian Sea.

Due to a large number of cyclones hitting the coast, the Bay of Bengal also holds the title of causing ‘80% of the world’s cyclone-related death. But why it is so?

Why does Bay of Bengal witness more cyclones?

The Bay of Bengal receives higher rainfall and constant inflow of fresh water from the Ganga and Brahmaputra rivers. With ample fresh water entering, the Bay’s surface water always remains refreshed, making it impossible for the warm water to mix with the cooler water below. This helps in formation of depressions.

Bay of Bengal is relatively shallow than the Arabian sea. The larger surface area of the Bay of Bengal allows faster heating causing higher evaporation. Faster evaporation forms a high-pressure zone in the area (evaporation leads to cooling resulting in high pressure) causing instability in the region. This makes Bay of Bengal suitable for cyclone formation.

The long and curved coastline of the Bay of Bengal results in amplified wind speeds as they funnel into the bay. This intensifies the storm raising its destructive potential.

The Bay of Bengal is surrounded by land on three sides, which generates additional moisture and instability.

The Bay of Bengal is also host to several cyclones formed in the Pacific Ocean. Due to lack of any major land mass between the Pacific Ocean and the Bay of Bengal, cyclonic winds easily move into the Bay of Bengal.

The low-lying coastal regions often get inundated when the storm makes landfall.

Why does Arabian Sea witness lesser cyclonic formation?

The Arabian Sea cyclones, historically have been fewer because of relatively colder sea surface temperatures. Nearly 48% of cyclones in the Arabian Sea never reached land, as opposed to only 13% in the Bay of Bengal.

The sea is also cooler than the Bay of Bengal, which makes it lesser prone to cyclones. The northern, central, and western parts of the Arabian Sea have much cooler temperatures.

Strong winds blow over the Arabian Sea to dissipate the heat. The mountains in east Africa direct winds toward the Arabian Peninsula, dissipating heat much more efficiently throughout the Arabian Sea.

Lack of constant fresh water supply to the Arabian Sea helps the warm water mix with the cool water, which reduces the surface temperature.

Most of the cyclones in the Arabian Sea are local. They collapse a little after making landfall as there is no back-up supply.

As a result, this region is not favourable to feed potential cyclones, and about half the cyclones that move into this area typically lose energy and dissipate.

However, from the past few years due to global warming the sea surface temperatures in the Arabian Sea continue to remain abnormally high, in the 30s, feeding cyclonic conditions.