Estimates of solar radiation over India

Abstract

Some of the empirical relationships developed for the estimation of global solar radiation from sunshine and cloudiness data are discussed, and based on data for more than five years from a network of 10 principal radiation stations, a regression formula has been derived for the Indian area. This equation is then applied to sunshine and cloudiness data from 52 Indian stations to obtain estimated values of global solar radiation for four representative months January, May, July and October. May is considered, instead of April, as the values obtained in that month are higher than in April.

Global solar radiation is seen to be a maximum, exceeding 620calfcmlfday, in May over northwestern parts of the country and a minimum, less than 320 cal/cm²/day, in January over northern India.

Values of out-going longwave radiation have also boon estimated, Using Brunt's empirical formula and net radiation values calculated, assuming various values of albedo for various types of Boil. It is Boon that the distribution of outgoing radiation follows the general climatic pattern as determined by the temperature and vapour pressure and net radiation does not vary appreciably over the whole country during the summer monsoon season.