Some features of the south-west monsoon rainfall of Cochin and Minicoy

Abstract

Several characteristics of (he south-west monsoon rainfall of the low latitude stations of Cochin (coastal) and Minicoy (island) have been studied using the hyetograms of these stations for the ten year period 1973-1982. Both stations exhibit diurnal variations of rainfall with maximum activity in the post-midnight hours and minimum in the afternoon hours. The amplitude of the diurnal variation increases for rain events of increasing intensities. The integrated duration of the seasonal rainfall is about 250 h at Cochin and 110 h al Minicoy. Half the total rain from heavy falls is received in a fifth of the total duration; half the total duration accounts for only a fifth of the total rain from light falls.The association between cumulative percentage rainfall (x) and cumulative percentage rain duration (y) is found to be of the form x = ay exp (by^c) where a, b and c are empirical constants. The average rain intensity varies from about I mm/h to 25 mm/h along this rainfall curve. An equation of the same form also gives a satisfactory representation of the variation of cumulative percentages of rain amount/rain-duration/rain hours with rain events of increasing amounts.