UPSC Current Affairs Snippet
- 1. (1) Why in news? As many as seven low-pressure areas (LPA) have formed in the North Indian Ocean region since October 1, 2021 — but none of them have intensified into a cyclone. This is unusual as October and November constitute the peak cyclone season for India, according to data from the India Meteorological Department (IMD). o No cyclone formation in the rest of November would mean a first-time anomaly in the last 31 years for October and November. o If December also remains cyclone-free, it would be the first time since 1961 that the post-monsoon season would remain without a cyclone. Why is this anomalous? This is happening despite the fact that the La Nina phase of the El Nino Southern Oscillation (ENSO) phenomenon is currently prevailing. The La Nina is the cooling phase of the ENSO and is generally favourable for cyclone / hurricane / typhoon formation all over the world, including in the North Indian Ocean region. The North Atlantic Ocean experienced record storm and hurricane activity due to the emergence of La Nina or due to its potential emergence in the last two years. The phenomenon creates an extended region of low vertical wind shear, which is favourable for the intensification of cyclones. What is the possible reason? When cyclones Gulab and Shaheen had formed successively around the end of September, it seemed like the cyclone season had started off. This had also come after the record-breaking formation of low- pressure areas in September that continued in October and November and caused excessive rainfall and floods in many parts of the country. The October floods in Kerala and Uttarakhand and the November floods in Tamil Nadu were caused partly by low-pressure areas. Along with this, the southwest monsoon season extended into late October. The monsoon finally retreated on October 26, 11 days later than the normal date of October 15. Monsoon had even started retreating only on October 6. The extension of the monsoon rainfall may be a reason for the lack of cyclones, according to experts. Its been observed that, low-pressure systems are only acting as self-inhibitors for strong cyclone growth. This is possible reason for low cyclogenesis this year, as per the IMD Why were there no cyclones in October and November this year? Indian Meteorological Department (IMD): • It is national meteorological service of the country and chief government agency dealing in everything related to meteorology, seismology and associated subjects. • It was formed in 1875. • It functions under Ministry of Earth Sciences. • It is headquartered in New Delhi. History of IMD: • Established in 1875 at Calcutta, by the British Government. • The first Director General of Observatories was Sir John Eliot The headquarters of IMD were later shifted to Shimla, then to Poona (now Pune) and finally to New Delh. GUIDANCE IAS
- 2. (2) It is notable that, exact reason for this anomaly is not known, further research on this issue is required to answer these questions. Additional information: What is a Tropical Cyclone? Tropical cyclones are low pressure systems that form over warm tropical waters. They typically form when the sea-surface temperature is above 26.5°C. Tropical cyclones can continue for many days, even weeks, and may follow quite erratic paths. A cyclone will dissipate once it moves over land or over cooler oceans. A more technical definition of a tropical cyclone is: “A non-frontal low pressure system of synoptic scale developing over warm waters having organised convection and a maximum mean wind speed of 34 knots or greater extending more than half-way around near the centre and persisting for at least six hours.” How do tropical cyclones form? A cluster of thunderstorms can develop over warm tropical oceans. If that cluster persists in an area of low pressure, it can start rotating. If the conditions are just right, the cluster of thunderstorms can grow in size and sustain itself and then develop into a tropical cyclone. Once developed, a tropical cyclone is like a giant, atmospheric heat engine. The moisture from the warm ocean acts as it's fuel, generating huge amounts of energy as clouds form. The rotating thunderstorms form spiral rainbands around the centre (eye) of the cyclone where the strongest winds and heaviest rain are found (eye wall), transporting heat 15 km or higher into the atmosphere. The drier cooler air at the top of the atmosphere becomes the exhaust gas of the heat engine. Some of the cool air sinks into the low-pressure region at the centre of the cyclone, hence causing the relatively calm eye. The eye is usually about 40 km wide but can range from 10 to over 100 km, with light winds and often clear skies. The rest of the cool air spirals outward, away from the cyclone centre, sinking in the regions between the rainbands. As long as the environmental conditions support this atmospheric heat engine, the tropical cyclone can maintain its structure and even intensify over several days. GUIDANCE IAS