Bay of Bengal Current Affairs

Scientists discover reasons behind 2015 Chennai Floods

A study conducted by the University of Hyderabad and the Indian Institute of Technology – Bombay has found out that the extreme El Nino conditions and warming of the Bay of Bengal had resulted in unprecedented heavy rainfall in Chennai for three days between November 30th to December 2nd in 2015.

Salient Findings

El Nino usually causes less than normal rainfall in the case of south-west monsoon. However, it does the reverse in the case of the northeast monsoon. It causes above-normal rainfall during the northeast monsoon. This is due to the difference in seasonal wind patterns between the two monsoons.

The researchers had carried out a simple linear correlation analysis that points out that the sea surface temperature at the Bay of Bengal is positively correlated with northeast monsoon rainfall. It has been found out that the magnitude of correlations of northeast monsoon rainfall with El Nino conditions and the Bay of Bengal warming to be almost same.

Based on several experiments, the scientists have attributed around 21% of the intensity of the extreme Chennai rainfall to the extreme El Nino condition

The consistent warming of the Bay of Bengal off the coast of Tamil Nadu and Andhra Pradesh is also considered as an important factor for the floods by the scientists.

However, scientists are yet to ascertain whether the contribution from the tropical Pacific to extreme rainfall during the northeast monsoon occurs only at the time of extreme El Nino or whether normal El Ninos too are capable of causing them.

El-Nino

El-Nino is a weather phenomenon, during which temperature at sea surface is warmer than normal sea-surface temperatures. El Nino is a warming of the Pacific Ocean between South America and the Date Line, centred directly on the Equator, and typically extending several degrees of latitude to either side of the equator. It accompanies high air surface pressure in the western Pacific. El Niño occurs when tropical Pacific Ocean trade winds die out and ocean temperatures become unusually warm

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Fact Box: Tropical Cyclone “Mora”

A deep depression in the Bay of Bengal has been declared intensified into a tropical cyclone named Mora. This is second cyclone in the Bay of Bengal after Maarutha, which helped bring in the Monsoon earlier by a week over Andaman & Nicobar Islands.

The tropical Cyclone Mora is likely to hit Bangladesh coast in next 24 hours and expected to cause heavy rains in West Bengal and North East Indian states. It may also help to pull monsoon faster over mainland.

About 2017 North Indian Ocean cyclone season

Every year, the North Indian Ocean cyclone season extends roughly between April to December with two peaks in May and November. This season includes cyclones in Bay of Bengal and Arabian sea, apart from Indian Ocean in northern hemisphere. The first cyclone of 2017 season was Cyclone Maarutha which was formed in April, 2017 triggering heavy rainfall in Sri Lanka, Myanmar and India’s Andaman & Nicobar Islands. Apart from other damages, three people were killed in Myanmar by Cyclone Maarutha. Cyclone Mora is second such cyclone in the Indian Ocean.

Naming of Tropical Cyclone

Tropical cyclones are classified into three main groups, based on intensity: tropical depressions, tropical storms, and a third group of more intense storms, whose name depends on the region. If a tropical storm in the North-western Pacific reaches hurricane-strength winds on the Beaufort scale, it is referred to as a typhoon. If a tropical storm passes the same benchmark in the Northeast Pacific Basin, or in the Atlantic, it is called a hurricane. Neither “hurricane” nor “typhoon” is used in either the Southern Hemisphere or the Indian Ocean. In these basins, storms of tropical nature are referred to simply as “cyclones”.

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