UPSC CSE Mains Syllabus: GS-1- Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity, cyclone etc.,
In news:
- For the first time in a century Mumbai will be hit by a cyclone.
• Cyclone Nisarga, which will have a direct impact on Maharashtra and Gujarat, is expected to land on 3 June.
• The state government has put in a range of disaster management teams with the Maharashtran coast bracing for a cyclone of 100-120 km / h wind speed, and high to extremely heavy rainfall likely in the isolated areas.
Nisarga was a name given by Bangladesh in a list, which has been formulated by a group of countries. The word ‘Nisarga’ means nature.
“If you take the Arabian Sea, the ocean is generally cooler than the Bay of Bengal and also has opposing winds in the atmosphere, especially during early monsoon or during monsoon. At the lower level of atmosphere, the winds may be blowing in one direction and on the upper level, it may be blowing in the opposite direction. This prevents the cyclone from developing vertically upwards.”
- Dr Roxy Mathew Koll, Scientist, Indian Institute of Tropical Meteorology, Lead Author, IPCC Oceans and Cryosphere.
This is the key reason for states like Maharashtra and Gujarat to have been relatively unscathed by cyclones in the past. But that is changing now.
Is Climate Change Causing Cyclone Nisarga?
- After much research, scientists agree that yes, climate change is one of the main reasons why cyclones have become stronger over the last few decades.
- Climate change has caused an increasein the temperature of the sea surface.
- Since cyclones are fuelled by heat, warmer seasmean more wind going upwards from the sea surface, causing higher wind speed, resulting in the storm emerging stronger.
- As a result of the rapid warming trend, even when the atmospheric conditions are not that favourable,like the early monsoon period is not at all favourable for cyclones to develop but the ocean conditions we see are quite favourable for intensification of such kind of systems, from low pressure systems to depression and then a cyclone.
- Temperatures in the Bay of Bengal were between 30-33°C priorto Cyclone Amphan.
- Global warming due to carbon emissions has also played a crucial role. The warm atmosphere causes higher water retention, this in turn leads to heavy rainfalland when coupled with a cyclone, cities are extremely prone to flooding.
Increasing frequency of cyclones:
Last year, however, was slightly unusual as the Arabian Sea saw the most frequent and intense cyclonic activity in more than 100 years, according to India Meteorological Department. Five cyclones originated in the area in 2019 — Vayu, Hikka, Kyarr, Maha and Pavan – when normally only one or two are formed.
How Will Nisarga Impact Mumbai?
- Mumbai is no stranger to heavy rainsand
- Every monsoon, low-lying areas of the city such as Hindmata, and areas in Dadar, Sion, Kurla, Santacruz among others, experience deluge.
- When coupled with a high tide, the water logging only gets worse.
But waterlogging is a very strong possibility. The impact of the waterlogging that is likely to ensue could have only been countered had the State implemented the recommendations of the Madhav Chitale Committee after studying the 2005 Mumbai floods that claimed thousands of lives.
The committee came up with four key observations and recommendations.
- The drainage linesin Mumbai were inadequate.
- Whatever available drainage line was there, a lot of them have been blocked or closed up by the societies or slum.
- Aside from encroachment, Mumbai has also lost a large chunk of its mangrovesover the last few decades.
- These mangroves are usually the first line of defencewhen battling natural disasters like cyclones and flooding.
| Tropical cyclone:· A tropical cyclone (TC) is a rotational low-pressure system in tropics when the central pressure falls by 5 to 6 hPa from the surrounding and maximum sustained wind speed reaches 34 knots (about 62 kmph).· It is a vast violent whirl of 150 to 800 km, spiraling around a centre and progressing along the surface of the sea at a rate of 300 to 500 km a day. Landfall:· A Landfall is the intersection of the center of a tropical cyclone with a coastline, according to the US National Hurricane Center.· Typically, in strong tropical cyclones, a landfall occurs when the eye of the cyclone moves over land. |
Cyclones are classified on the basis of the wind speed.
- Depression – 20–31 mph (31–49 km/h).
- Deep Depression– 50–61 km/h.
- Cyclonic storm: 62–88 km/h.
- Severe Cyclonic Storm: 89–117 km/h.
- Very Severe Cyclonic Storm: 118–166 km/h.
- Extremely Severe Cyclonic Storm: 166–221 km/h.
- Super Cyclonic Storm: The highest classification used in the North Indian Ocean is a Super Cyclonic Storm, which have hurricane-force winds of above 222 km/h.
What are the Precautions Taken by the State?
- Maharashtra Chief Minister held review meetings with the departments overlooking preparedness for the cyclone on Tuesday, 2 June.
- The CM appealed to citizens to stay indoors for the next two days.
- The Mumbai Police released an order prohibiting any presence or movement in places along the coast like beaches, promenades, parks, and other places along the coastline.
- Mumbai fire brigade, too, is on alert. Twelve teams of brigade personnel and rescue boats have been kept on standby.
Source:” Indian Express“.
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