Time series analyses of annual rainfall over India

Abstract

The available rainfall series extending to more than 100 years for 23 stations representing different parts of India have been examined with different types of low pass filters in order to find out trends and periodicities in these series. The long period trend shown by some of the series has been compared with that shown by sunspot numbers the series of which from 1940 onwards was treated with the same low pass filter. The rainfall series have also been treated with band pass filter and power spectrum analysis for finding out of periodicities in them. It is seen that rainfall of west coast stations north of Trivandrum as well as the sunspot cycles have shown an increasing trend from the beginning of the century till the sixties, the trends for Veraval, Bombay, Ratnagiri and Vengurla being statistically significant. Other results of the study have been given in the conclusion.