Tropical Cyclone Nivar

Cyclone Nivar is a tropical cyclone which are large storms that form over warm ocean waters. Cyclone Nivar impacted Tamil Nadu, Andhra Pradesh, Telangana and southern Karnataka with heavy rains, strong winds and coastal flooding on 24 & 25th November 2020. It was classified as a Very Severe Cyclonic Storm as it reached speeds of 120 km/h. It caused about 5000 crores in damages in just two days.

The term "cyclone" comes from the Greek word "cyclos," as when they approach they look like "coils of a snake". The ocean is filled with warm water. This warm water heats up the air above it, causing it to rise. This rising air is like a hot air balloon, filled with water vapor that it collected from the ocean. As the warm air rises, it leaves a low-pressure zone behind at the ocean's surface. This zone tries to suck in more air. Cooler air rushes in to fill this low-pressure vacuum. However, due to the Earth's rotation, this rushing air doesn't just fill the hole straight down. Instead, it starts to spin, creating a swirling vortex. This is why the winds look like a coiling snake.

Tropical cyclone Nivar started due to disturbance in the inter-tropical convergence low pressure zone. This tropical depression formed over the Bay of Bengal and made landfall near Pondicherry. However, it did not immediately dissipate. It become a Deep Depression in Bay of Bengal and made a second landfall on the Andhra Pradesh coast. It caused extensive damage and a few people also died.

Disaster Relief Response in India to Cyclone Nivar

• Tropical Cyclone Nivar caused a lot of flooding in areas of Chennai in Tamil Nadu in November 2020.
• Five people were killed in Tamil Nadu, and eight in Andhra Pradesh.
• The initial damage to agriculture and other sectors in Puducherry was estimated at ₹4 billion (US$54.2 million).
• The government sent six National Disaster Response Force (NDRF) teams and told officials to evacuate people in risky areas.
• The Tamil Nadu government alsostored food and fuel for people affected by the cyclone.

Cyclones are classified into two main types: extra-tropical and tropical.

• Tropical cyclones develop in the regions between the Tropics of Capricorn and Cancer. They are large-scale weather systems that form over tropical or subtropical waters.
• The air of the cyclone circulates inward in an anticlockwise direction in the Northern hemisphere and clockwise in the Southern hemisphere.

1. Cyclones are caused by atmospheric disturbances around a low-pressure area, which has strong and often destructive winds. Over warm ocean waters, low pressure system forms due to rising hot air.
2. This air contains water content as it is rising from the Ocean. This leads to formation of thunderstorms. These thunderstorms, in the rig ht condition cluster and get strengthened with continuous supply of water from the ocean.
3. When this developing storm reaches land (landfall), it ends because it no more has the ocean supply from the water.

Cyclones are classified by wind speed and damage capacity:

• High Frequency:The Indian subcontinent is one of the world's most vulnerable regions to tropical cyclones. With a long coastline of 7,516.6 km, it is exposed to nearly 10% of the world's tropical cyclones.
• Seasonal: Tropical cyclones in India typically occur in the months of May-June and October-November. They are most intense and frequent in the North Indian Ocean (Bay of Bengal and Arabian Sea) during November and May.
• Eastern Bias: Most cyclones originate in the Bay of Bengal, hitting the East coast. On average, five to six cyclones form every year, with two or three being severe. Cyclones are more frequent in the Bay of Bengal than the Arabian Sea with an approximate ratio of 4:1.
• High Damage: The disaster potential of tropical cyclones in India is particularly high during landfall (when a storm or cyclone reaches land after traveling over water) due to the accompanying destructive winds, storm surges, and torrential rainfall. Storm surges (a sudden and dangerous rise in sea level), in particular, cause extensive damage by inundating low-lying coastal areas, causing floods, eroding beaches and embankments, destroying vegetation, and reducing soil fertility.

• Defining Tropical Cyclone: The World Meteorological Organization (WMO) uses the term "tropical cyclone" to describe weather systems with winds exceeding 34 knots which is called the gale force (63 kilometers per hour). Tropical cyclones are fueled by the heat from the sea and driven by easterly trades and temperate westerlies.
• Regional Centres: WMO has six regional specialised meteorological centres (RSMCs) and five regional Tropical Cyclone Warning Centres (TCWCs) across the globe to monitor cyclone formation, issue advisories and name cyclones.
• The Indian Meteorological Organisation (IMD): is the RSMC in the Northern Indian Ocean. It provides advisories to 13 countries in the north Indian Ocean basin: Bangladesh, India, Iran, Maldives, Myanmar, Oman, Pakistan, Qatar, Saudi Arabia, Sri Lanka, Thailand, United Arab Emirates and Yemen.

WMO names cyclones through suggestions from countries in the region. In 2020, the latest list was released which includes 13 names for cyclones, each contributed by one of the 13 member countries, for a total of 169 names. Thenames from India include Gati, Tej, Murasu, Aag, Vyom, Jhar, Probaho, Neer, Prabhanjan, Ghurni, Ambud, Jaladhi, and Vega.

The name Nivar was given by Iran. Some of the most important criteria for naming cyclones are that the names should be politically and culturally neutral, not rude or cruel, and short and easy to pronounce. The maximum length of a cyclone name is eight letters.

Cyclone Nivar was a strong storm that caused a lot of damage. But it also reminded us that natural disasters demand both immediate response and long-term planning. The relief efforts after the cyclone showed that we need to be proactive. The quick response by the National Disaster Response Force (NDRF) and the evacuation plans showed how important it is to be coordinated and prepared. These actions not only save lives but also minimize the economic and social impact of such calamities.

Countries like Japan and Bangladesh are disaster prone but also set excellent examples for disaster prepardness through resillient infrastructure, localised disaster plans, volunteer forces, early warning of impending disaster.

It is important to understand the science behind tropical cyclones so we can develop effective strategies to deal with them. In the future, we need to learn from our experiences and invest in research, infrastructure, and community education. By combining scientific knowledge, international cooperation, and community involvement, we can work towards a future where the impact of these natural disasters is minimized, and the well-being of vulnerable communities is protected.