explain what is southern oscillation and how is it connected to the indian monsoon phenomena
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Annual average monsoon precipitation in India over 110 years. The long-term average has been 899 millimeters of precipitation.[1] However, the monsoon varies over the Indian subcontinent within a ±20% range. Rains that exceed 10% typically lead to major floods, while a 10% shortfall is a significant drought.[2]
The monsoon of South Asia is among several geographically distributed global monsoons. It affects the Indian subcontinent, where it is one of the oldest and most anticipated weather phenomena and an economically important pattern every year from June through September, but it is only partly understood and notoriously difficult to predict. Several theories have been proposed to explain the origin, process, strength, variability, distribution, and general vagaries of the monsoon, but understanding and predictability are still evolving.
The unique geographical features of the Indian subcontinent, along with associated atmospheric, oceanic, and geophysicalfactors, influence the behavior of the monsoon. Because of its effect on agriculture, on flora and fauna, and on the climates of nations such as India, Nepal, Bangladesh, Bhutan, Pakistan, and Sri Lanka — among other economic, social, and environmentaleffects — the monsoon is one of the most anticipated, tracked,[3] and studied weather phenomena in the region. It has a significant effect on the overall well-being of residents and has even been dubbed the "real finance minister of India".[4][5]
The monsoon of South Asia is among several geographically distributed global monsoons. It affects the Indian subcontinent, where it is one of the oldest and most anticipated weather phenomena and an economically important pattern every year from June through September, but it is only partly understood and notoriously difficult to predict. Several theories have been proposed to explain the origin, process, strength, variability, distribution, and general vagaries of the monsoon, but understanding and predictability are still evolving.
The unique geographical features of the Indian subcontinent, along with associated atmospheric, oceanic, and geophysicalfactors, influence the behavior of the monsoon. Because of its effect on agriculture, on flora and fauna, and on the climates of nations such as India, Nepal, Bangladesh, Bhutan, Pakistan, and Sri Lanka — among other economic, social, and environmentaleffects — the monsoon is one of the most anticipated, tracked,[3] and studied weather phenomena in the region. It has a significant effect on the overall well-being of residents and has even been dubbed the "real finance minister of India".[4][5]
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SOUTHERN OSCILLATION--El Niño–Southern Oscillation (ENSO) is an irregularly periodic variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean, affecting climate of much of the tropics and subtropics. The warming phase of the sea temperature is known as El Niño and the cooling phase as La Niña.
The interannual fluctuations in the Southern Oscillation indices (Wright, 1975) and their relations to the Indian monsoon (June-September) rainfall have been examined for the period of 106 years from 1875 to 1980. The monsoon rainfall is significantly (99.9 per cent level) correlated with the Southern Oscillation indices for the seasons: MJJ (0.59), ASO (0.67), NDJ (0.53), and FMA of the following year (0.38). The fluctuations in the Southern Oscillation index for the ASO season appear strongly related to the nearly simultaneous monsoon rainfall of India. This implies that the large positive (negative) value of the Southern Oscillation index, signifying strengthening (weakening) of the Walker circulation coincides with large excess (deficient) monsoon rainfall over India. The coherence spectrum reveals that the Southern Oscillation index and the monsoon rainfall are highly correlated in the period range of about 2–2.5 years and 4–6 years. The first of these periods corresponds with the Quasi-Biennial Oscillation and the latter agrees with the features of the Southern Oscillation, suggesting a strong link between Indian monsoon rainfall and these two phenomena. The striking feature of the composites of the Southern Oscillation index averaged for all the drought years and for all the flood years is the simultaneous occurrence of low (high) Southern Oscillation index and droughts (floods) in India. However, this association has limited use in long-range prediction. A preliminary study suggests that a nearly simultaneous occurrence of major climatic anomalies of the tropics, such as droughts in India and El Niño off the coast of Peru, are linked to the Southern Oscillation, indicating some kind of time dependent zonal east-west circulation, i.e. Walker circulation.
The interannual fluctuations in the Southern Oscillation indices (Wright, 1975) and their relations to the Indian monsoon (June-September) rainfall have been examined for the period of 106 years from 1875 to 1980. The monsoon rainfall is significantly (99.9 per cent level) correlated with the Southern Oscillation indices for the seasons: MJJ (0.59), ASO (0.67), NDJ (0.53), and FMA of the following year (0.38). The fluctuations in the Southern Oscillation index for the ASO season appear strongly related to the nearly simultaneous monsoon rainfall of India. This implies that the large positive (negative) value of the Southern Oscillation index, signifying strengthening (weakening) of the Walker circulation coincides with large excess (deficient) monsoon rainfall over India. The coherence spectrum reveals that the Southern Oscillation index and the monsoon rainfall are highly correlated in the period range of about 2–2.5 years and 4–6 years. The first of these periods corresponds with the Quasi-Biennial Oscillation and the latter agrees with the features of the Southern Oscillation, suggesting a strong link between Indian monsoon rainfall and these two phenomena. The striking feature of the composites of the Southern Oscillation index averaged for all the drought years and for all the flood years is the simultaneous occurrence of low (high) Southern Oscillation index and droughts (floods) in India. However, this association has limited use in long-range prediction. A preliminary study suggests that a nearly simultaneous occurrence of major climatic anomalies of the tropics, such as droughts in India and El Niño off the coast of Peru, are linked to the Southern Oscillation, indicating some kind of time dependent zonal east-west circulation, i.e. Walker circulation.
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