IMD Forecasts and EL Nino

IMD Forecasts and EL Nino

Part of: GS-I- Geography (PT-MAINS-PERSONALITY TEST)

Indian Meteorological Department (IMD):

• A disastrous tropical cyclone struck Calcutta in 1864 and this was followed by failures of the monsoon rains in 1866 and 1871. In the year 1875, the Government of India established the India Meteorological Department, bringing all meteorological work in the country under a central authority.
• The first Director General of Observatories was Sir John Eliot who was appointed in May 1889 at Calcutta headquarters. The headquarters of IMD is at New Delhi.
• In the telegraph age, it made extensive use of weather telegrams for collecting observational data and sending warnings.
• IMD became the first organisation in India to have a message switching computer for supporting its global data exchange.
• India was the first developing country in the world to have its own geostationary satellite, INSAT, for continuous weather monitoring of this part of the globe and particularly for cyclone warning.

IMD has continuously ventured into new areas of application and service, and steadily built upon its infra-structure in its history of 140 years. It has simultaneously nurtured the growth of meteorology and atmospheric science in India. Today, meteorology in India is poised at the threshold of an exciting future.

IMD Mandate:

India Meteorological Department was established in 1875. It is the National Meteorological Service of the country and the principal government agency in all matters relating to meteorology, seismology and allied subjects.

• To take meteorological observations and to provide current and forecast meteorological information for optimum operation of weather-sensitive activities like agriculture, irrigation, shipping, aviation, offshore oil explorations, etc.
• To warn against severe weather phenomena like tropical cyclones, norwesters, duststorms, heavy rains and snow, cold and heat waves, etc., which cause destruction of life and property.
• To provide meteorological statistics required for agriculture, water resource management, industries, oil exploration and other nation-building activities.
• To conduct and promote research in meteorology and allied disciplines.
• To detect and locate earthquakes and to evaluate seismicity in different parts of the country for development projects.’

IMD Forecasts:

• Seasonal rainfall is likely to be 100% of the Long Period Average (LPA) with a model error of ± 5%, the IMD said.
• A total of around 88 cm rainfall is forecast during the monsoon months from June to September.
• The monsoon season in 2019 breached many records across India with a total of 968.3 mm rainfall.
• The forecast probability, as reported by IMD, indicates 20 per cent chances of below-normal (90-96% of LPA), 41 per cent chances of normal (96-104%) and 21 per cent chances of above-normal rainfall (104-110%).
• Further, the IMD report also states that neutral El Niño–Southern Oscillation (ENSO) conditions would be neutral over the Pacific Ocean during the monsoon season, with some models indicating the possibility of weak La Niña conditions during the second half of the season.
• The hero of monsoon 2019, Indian Ocean Dipole (IOD) is also likely to remain neutral during monsoon season.
• The sea surface temperature conditions over the Pacific and Indian Oceans, as indicated by ENSO and IOD, play a crucial role in determining the amount of rainfall and its distribution across India during the monsoon season.
• While El Niño has an adverse impact on the monsoon rainfall, a strong positive IOD (like 2019) and La Niña conditions contribute to enhancing the overall rainfall across India.

El Nino:

• El Nino refers to the large-scale ocean-atmosphere climate interaction linked to a periodic warming in sea surface temperatures across the central and east-central Equatorial Pacific. It is associated with high pressure in the western Pacific.
• El Nino adversely impacts the Indian monsoons and hence, agriculture in India.
• The cool surface water off the Peruvian coast goes warm because of El Nino. When the water is warm, the normal trade winds get lost or reverse their direction.
• Hence, the flow of moisture-laden winds is directed towards the coast of Peru from the western Pacific (the region near northern Australia and South East Asia).
• This causes heavy rains in Peru during the El Nino years robbing the Indian subcontinent of its normal monsoon rains.
• The larger the temperature and pressure difference, the larger the rainfall shortage in India.

La Nina

• La Nina means ‘little girl’ in Spanish and is also known as El Viejo or ‘cold event’. Here, the water temperature in the Eastern Pacific gets colder than normal. As a result of this, there is a strong high pressure over the eastern equatorial Pacific. Now, there is low pressure in the Western Pacific and off Asia.
• La Nina causes drought in Peru and Ecuador, heavy floods in Australia, high temperatures in Western Pacific, Indian Ocean, off the Somalian coast and good monsoon rains in India. A La Nina is actually beneficial for the Indian monsoon.
• Generally, El Nino and La Nina occur every 4 – 5 years. El Nino is more frequent than La Nina. Typically, the episodes last for nine to twelve months.

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