Annual rain‐water over India, its variability and impact on the economy

Abstract

The total volume of rain-water over India has been computed for each of the years during the period 1871-1978 on the basis of the rainfall data for a fixed network of 306 raingauges. The mean, the standard deviation and the coefficient of variation of the series of annual rain-water volume are 3143 km3, 300 km3 and 9.5 per cent, respectively. The series is homogeneous and random. The serial correlation is 0.013 which is too low to suggest any relationship between successive terms. Gaussian distribution gives a good fit to the series.The series giving the percentage area of the country with a deficiency of 20 per cent or more, as well as the percentage area with an excess of 20 per cent or more have been obtained. These bring out the variability in the deficiency and excess of rain-water over the country during the period. The years of well-marked rain-water deficiencylexcess over India have been identified by utilizing the criterion of 40 per cent or more area under rain-water deficiency/excess. The occurrence of such years has been found to be random and the number of such years in five-year periods appears to be distributed in accordance with the Binomial and the Poisson Probability models.The impact of marked deficiency/excess on the All India Index of food grain prices and A l l India Index of food grain production has been examined. It is found that the impact of well-marked deficiency can generally be seen clearly but that of well-marked excess is seen clearly in some cases only. This is understandable. Overall excess in a year may or may not result in floods which have the potentiality to damage crops. The impact of the well-marked deficiency of 1918 has been maximum.Remedial measures which would make the economy of the country less dependent on the variability of the annual rain-water have been discussed.

Impact of El Niño–southern oscillation on Indian foodgrain production

“…The Indian summer monsoon, which provides 75 to 90% of the total annual rainfall over most parts of India during the 4 months from June to September, is vital to India's agriculture (Parthasarathy et al, 1992). The Indian monsoon circulation influences more than 60% of the Earth's population (Webster et al, 1998) due to its large-scale impact on food production, power generation, drinking water supply and overall economy (Mooley et al, 1981;Mooley and Parthasarathy, 1983;Parthasarathy et al, 1988a).…”

Decadal frequency and trends of extreme excess/deficit rainfall during the monsoon season over different meteorological sub-divisions of India

“…2. The data for various periods were collected from different publications and Government sources, and the India Meteorological Department (Mooley et al 1981). The homogeneity or stationarity of the monthly data series was tested by the Swed and Eisenhart test and the Mann-Kendall rank test (WMO 1966), and it was found that, for all sub-divisions, the number of runs lies within the required limits of the 5% significance level (Parthasarathy et al 1987).…”

“…The nature of the frequency distribution has also been tested using the chi-square statistic with 10 equalprobability class-intervals (Cochran 1952). Mooley and Parthasarathy (1984), Parthasarathy et al (1990Parthasarathy et al ( , 1992Parthasarathy et al ( , 1993Parthasarathy et al ( , 1994Parthasarathy et al ( , 1995, Pant and Rupakumar (1997) and Mooley et al (1981) provide more detailed discussion of the methodology adopted for assessing the quality, completeness and homogeneity of these data sets.…”

Role of natural external forcing factors in modulating the Indian summer monsoon rainfall, the winter North Atlantic Oscillation and their relationship on inter-decadal timescale

“…It brings approximately 80 % of the region's annual rainfall. The ISM plays a key role in Indian agriculture, and its anomaly often results in huge economic and societal consequences (Mooley et al 1981;Mooley and Parthasarathy 1982).…”