IMD MONSOON FORECAST
- Ocean currents transport heat from one region to another, affecting sea surface temperatures. Warmer SSTs provide more energy and moisture to the atmosphere, which can enhance the intensity of monsoon rains. Cooler SSTs, on the other hand, can suppress rainfall by reducing moisture availability and destabilizing atmospheric conditions
- Ocean currents play a crucial role in supplying moisture to the atmosphere. Warm ocean currents increase evaporation rates, leading to higher atmospheric moisture content. This moisture is then transported inland by prevailing winds, contributing to the development of rainfall during the monsoon season
- Ocean currents influence atmospheric circulation patterns, such as the formation of high and low-pressure systems. These pressure systems, in turn, drive the movement of air masses and the onset, duration, and intensity of the monsoon. For example, the interaction between ocean currents and the atmosphere in the Indian Ocean can influence the position and strength of the Indian summer monsoon
- Changes in ocean currents can alter regional climate patterns, including the distribution of rainfall and temperature. Variations in ocean currents, such as El Niño and La Niña events in the Pacific Ocean, can disrupt normal monsoon patterns by affecting atmospheric circulation and SSTs, leading to droughts or floods in affected regions
- Ocean-atmosphere interactions create feedback mechanisms that can amplify or dampen the effects of the monsoon. For example, warm SSTs can enhance atmospheric convection and cloud formation, leading to increased rainfall. Conversely, cooler SSTs can inhibit convection and reduce rainfall, creating a feedback loop that influences the strength and duration of the monsoon
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North Atlantic Drift (Gulf Stream): This warm ocean current flows from the Gulf of Mexico northeastward along the eastern coast of North America before turning eastward toward Europe. It impacts the climate of the eastern United States and Western Europe.
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Kuroshio Current: The Kuroshio is a strong western boundary current in the North Pacific Ocean. It flows northeastward along the eastern coast of Taiwan and Japan before turning eastward toward the North Pacific. The Kuroshio influences weather patterns and marine ecosystems in the region.
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East Australian Current: This warm ocean current flows southward along the eastern coast of Australia, transporting warm tropical waters toward the temperate regions of the southeast. It influences the climate and marine biodiversity along the Australian coast.
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Peru Current (Humboldt Current): The Peru Current is a cold ocean current that flows northward along the western coast of South America, originating from Antarctica. It brings cold, nutrient-rich waters to the surface, supporting productive fisheries off the coast of Peru and Chile.
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California Current: This cold ocean current flows southward along the western coast of North America, parallel to the coast of California. It originates from the North Pacific and influences the climate and marine ecosystems of the region.
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Agulhas Current: The Agulhas is a warm ocean current that flows southward along the eastern coast of Africa, transporting warm Indian Ocean waters toward the Southern Ocean. It plays a significant role in the climate and marine ecology of the Indian Ocean region.
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North Pacific Current: This warm ocean current flows eastward across the North Pacific Ocean, between Japan and the Aleutian Islands. It influences the climate and marine habitats in the North Pacific region.
- The Southwest Monsoon, also known as the summer monsoon, is a seasonal wind pattern that brings heavy rainfall to the Indian subcontinent and surrounding regions during the summer months. It is one of the most significant weather phenomena in South Asia and has a profound impact on the region's climate, agriculture, economy, and society.
- The Southwest Monsoon typically occurs from June to September, originating from the Indian Ocean and Arabian Sea. During the summer months, the landmass of the Indian subcontinent heats up more rapidly than the surrounding ocean waters. This temperature difference creates a low-pressure area over the Indian subcontinent, drawing moist air from the Indian Ocean.
- As the warm, moisture-laden air moves inland, it encounters the Western Ghats mountain range along the western coast of India. The Western Ghats act as a barrier, forcing the moist air to ascend and cool rapidly, leading to condensation and the formation of heavy rainfall. This phenomenon is known as orographic rainfall.
- The Southwest Monsoon winds also interact with the Himalayas in northern India, leading to orographic rainfall in the foothills and contributing to the formation of major river systems such as the Ganges, Brahmaputra, and Indus.
- The onset and intensity of the Southwest Monsoon are influenced by various factors, including sea surface temperatures, atmospheric pressure patterns, and the presence of phenomena such as the El Niño-Southern Oscillation (ENSO).
- The Southwest Monsoon is crucial for agriculture in the Indian subcontinent, as it provides the majority of the region's annual rainfall. Farmers rely on the monsoon rains to irrigate crops such as rice, wheat, and sugarcane, which form the backbone of the region's economy
- IMD forecasts the monsoon condition every year. It has predicted a good monsoon rainfall during the southwest monsoon season
- The transition of the weakening El-Nino into a neutral condition ahead of the monsoon onset. EL-Nino is associated with suppressed rainfall during the Indian monsoon.
- The emergence of La-Nina during the second-half of the monsoon is expected to bring higher than normal rainfall over the country. La-Nina is known to help rainfall activity during monsoon.
- There is a possibility of a positive phase of the Indian Ocean Dipole (IOD). IOD is the Indian Ocean counterpart of El Nino. The positive phase of IOD is good for rainfall over India.
- Another positive factor is the below average snow cover along Eurasia and the northern hemisphere during December-March
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IMD has categorized rainfall during monsoon on the 50-year average of rainfall: Rainfall between 105-110%: Above normal rainfall Rainfall between 96%-104%: Normal rainfall Rainfall between 90-95%: Below normal rainfall Rainfall less than 90%: Deficient rainfall |
The El Niño-Southern Oscillation (ENSO) is a climate phenomenon characterized by fluctuations in sea surface temperatures (SSTs) and atmospheric pressure across the equatorial Pacific Ocean. It has significant impacts on weather patterns, temperature, and precipitation around the globe.
ENSO consists of three phases:
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El Niño: During El Niño events, warmer-than-average sea surface temperatures develop in the central and eastern Pacific Ocean, near the coast of South America. This warming disrupts normal atmospheric circulation patterns, leading to changes in weather and climate across the Pacific and beyond. El Niño typically brings drier and warmer conditions to the western Pacific, including Australia and Indonesia, while increasing rainfall in the central and eastern Pacific, including parts of South America.
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La Niña: La Niña events are characterized by cooler-than-average sea surface temperatures in the central and eastern Pacific Ocean. This cooling enhances normal atmospheric circulation patterns, leading to opposite effects compared to El Niño. La Niña often brings increased rainfall to the western Pacific, including Australia and Indonesia, while causing drier and cooler conditions in the central and eastern Pacific, including parts of South America.
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Neutral: Neutral conditions occur when sea surface temperatures in the equatorial Pacific are near average. During neutral phases, ENSO does not exert a significant influence on global weather patterns, although other climate drivers may still play a role
In a normal year, the eastern side of the Pacific Ocean, near the northwestern coast of South America, is cooler than the western side near the islands of Philippines and Indonesia. The reason for this is the prevailing wind systems that move from east to west sweep the warmer surface waters towards the Indonesian coast. The relatively cooler waters from below come up to replace the displaced water
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For Prelims: Indian and World Geography – Physical, Social, Economic geography of India and the World. For Mains: GS-I, Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity, cyclones. etc., geographical features and their location-changes in critical geographical features (including water-bodies and ice-caps) and in flora and fauna and the effects of such changes |
