Context: Climate scientists say the Bay of Bengal, where Cyclone ‘Yaas’ has formed, is at least two degrees warmer than what is normal for this time of the year. Background: Generally, cyclones in the Bay of Bengal are ferocious and cause significant devastation. This year, the north Bay of Bengal is exceptionally warm with temperatures up to 32 degrees Celsius. Recent cyclones in Bay of Bengal: 1. Amphan was a super cyclone that ravaged West Bengal in March last year. It was the strongest storm that hit India’s eastern coast since the super cyclone of 1999, that struck Paradip, Odisha. 2. Before Amphan, Fani in 2019 also hit Odisha, causing immense damage that lasted weeks. What’s the concern? In the last four years 12 cyclones have formed in the Bay. Out of five cyclones that the Indian coastline witnessed in a year, four originated in the Bay of Bengal and only one in the Arabian Sea. 1. There is also increasing frequency of cyclone formation in the North Indian Ocean in recent years. Why Bay of Bengal is the hot-bed for cyclonic storms? 1. The vast low pressure created by the warm water of the ocean. 2. The Bay of Bengal shaped like a trough that makes it more hospitable for storms to gain force. 3. The high sea surface temperature makes matters more worse in the Bay triggering the intensity of the storms. 4. The Bay of Bengal also gets more rainfall with sluggish winds and warm air currents around it that keep temperatures relatively high all year. 5. The constant inflow of fresh warm water from the perineal rivers like Bramhaputra, Ganga makes it further impossible to mix with the cooler water below. 6. Lack of landmass between the Pacific Ocean and the Bay of Bengal tend cyclonic winds to move into the coastal areas causing heavy rainfall. 7. The absence of air movements from north-western India towards the Bay in the post-monsoon phase is also another reason for the chances of cyclones in the Bay of Bengal. What geographical advantage the Arabian sea has? 1. It is much calm as the stronger winds help dissipate the heat. 2. Lack of constant fresh water helps the warm water to mix with the cool water underneath, reducing the surface temperature. 3. The Arabian Sea enjoys the locational advantage as the winds from the Pacific Ocean encounter the Western Ghats and the Himalayas cutting down on its intensity and sometimes never reaching the Arabian Sea.

Context: The India Meteorological Department (IMD) has informed that a low pressure area is formed over north Andaman Sea and adjoining east central Bay of Bengal around May 22. 1. It is likely to intensify into a cyclonic storm by May 24. It has been named as Cyclone Yaas. The name was given by? 1. The name ‘Yaas’ was suggested by Oman and refers to a tree with good fragrance and in English, the word is similar to Jasmine. 2. The next cyclone—after Yaas—is likely to be named Gulab, suggested by Pakistan. How are cyclones formed? Cyclones are formed over the oceanic water in the tropical region. In this region, the sunlight is highest which results in warming of land and water surface. Due to warming of the surface, the warm moist air over the ocean rises upwards following which cool air rushes in to fill the void, they too get warm and rise — the cycle continues. But what creates the spin? Wind always blows from high pressure to low pressure areas. High pressure areas are created in the cold region while low is created in the warm regions. Polar regions are high pressure areas as the amount of sunlight here is less than the tropical region. So, wind blows from polar regions to tropical regions. 1. Then comes the Earth’s movement, which is west to east. The Earth’s rotation on its axis causes deflection of the wind (in the tropical region as the speed of spinning of Earth is higher compared to polar sides due to its spherical shape — blowing from both the polar regions. Wind coming from the Arctic is deflected to the right while Antarctic wind deflects to the left side. 2. So, wind is already blowing in a direction. But when it reaches the warmer place, cool air starts getting attracted to the centre to fill the gap. So while moving to the centre, cool air keeps getting deflected resulting in circulation of wind movement — this process continues until the cyclone hits the land. What happens when a cyclone hits the land? Cyclone dissipates when it hits the land as the warm water that rises and creates space for cool water is no longer available on land. Also, the moist air that rises up forms clouds leading to rains that accompany gusting winds during cyclones. Sources: the Hindu.

Context: A mesmerising phenomenan — a rainbow around the Sun know as a Sun halo, was observed recently in Bengaluru. What is it? How is it formed? The halo that appeared around the Sun is a 22-degree ring that appears due to the dispersion of light as white light passes through ice crystals found in upper-level cirrus clouds, causing the halo to have colours. 1. The clouds contain millions of tiny ice crystals, which refract, split and even reflect the light to give an impression of a circular rainbow ring. 2. The crystals have to be oriented and positioned just so with respect to your eye, in order for the halo to appear. Similarly, what are lunar halos? Seen around the Moon, lunar halos are mostly colourless as moonlight is not very bright. Sources: the Hindu.

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