Day 44 – 4. Which parts of the globe are more susceptible to damage by cyclones and why? Explain with the help of suitable examples.
4. Which parts of the globe are more susceptible to damage by cyclones and why? Explain with the help of suitable examples.
विश्व के किन हिस्सों में चक्रवात से नुकसान की आशंका अधिक है और क्यों? उपयुक्त उदाहरणों की सहायता से समझाएँ।
Cyclones are low pressure centres, surrounded by closed isobars, which involve a closed circulation about the low pressure centre. The air moves anticlock wise in northern hemisphere and clockwise in southern hemisphere.
They can be classified either on the basis of their geographical location (tropical/ temperate cyclones) or on the basis of their nature (cold /warm core cyclone). They play a vital role in exchange of heat between different latitude zones and also transfer humidity form one part of the earth to another.
Regional distribution of tropical cyclones:
There are six regions that are more vulnerable to tropical cyclones:
- Tropical North Atlantic (Gulf of Mexico, West Indies and Caribbean Sea): Cyclones in this region is known as Hurricane, occur mainly during August-October. Main reasons being increased sea surface temperature, convective instability, low wind shear and other thermodynamic activities. Examples-Hurricane Katrina, Florence etc.
- Eastern part of the tropical north pacific (Western coast of Mexico and Central America): also known as Hurricane, usually observed during June-July. The shifting of Intertropical Convergence Zone (ITCZ) northwards and low pressure formed, aided by northwest movement of wind (due to Coriolis force) favours the formation of Tropical Cyclone in this region.
- Western part of tropical north pacific (The Philippines, the China Sea and areas around Japan): The cyclones in this region are called as Typhoon, occurs during months of June-December. The presence of low vertical wind shear of less than 10 metres/second, monsoon trough and atmospheric instability favours development of tropical Typhoons.
- Bay of Bengal and Arabian Sea: They are more frequent during June-September, high sea temperature along with the low pressure regions, sometimes the typhoons originating in western pacific too help in cyclone formation. Ex-Fani, Ochkhi etc
- Western South Pacific Ocean (regions of Samoa, Fiji Island and the east and north coast of Australia): Occur during January-March season. They too are result of high surface temperature and low vertical wind shear that result in atmospheric instability and heavy cloudiness.
- The south coast of Indian Ocean (coastal regions of Madagascar): Occurs during January-March and the westward movement of tropical depression intensified by low vertical wind shear favours cyclone formation. One dangerous recent event is the Idai Cyclone (March 2019) that resulted in more than 1300 deaths and several missing cases.
Temperate cyclones are majorly dynamic in origin (Movement of air masses and coriolis force- Frontogenesis), they occur during winter seasons and are away from equator region. They are largely non-destructive due to slow moving winds, but there might be damage due to flooding. They can occur both on land and water. They occur scattered but irregular intervals throughout the zone of westerlies. They impact mainly in Northern hemisphere (due to less land availability in Southern Hemisphere).
They impact Indian climate in the form of Western disturbances. Though, they are beneficial, as they aid in wheat, saffron cultivation, sometimes they have negative implications too. Excessive rainfall causes landslides, floods, avalanches etc., and occasionally brings cold wave and dense fog like condition that damages the crop in Indo-Gangetic plains.
Around 8 percent of total land area in India is prone to cyclones. The cyclonic storms are associated with heavy rains, thunderstorms, high tides and intense winds that cause heavy destruction in coastal areas. Proper implementation of National Cyclone Risk Mitigation Project(NCRMP) that include improved early warning dissemination system, capacity building of local communities to respond, and strengthening the rehabilitation mechanism would minimize the damage.