Objective determination of northeast monsoon onset dates over coastal Tamil Nadu for the period 1901-90

Abstract

The onset dates of northeast monsoon over coastal Tamil Nadu have been determined by adopting an objective method for the years 1901-90. The various statistical parameters associated with onset dates have been computed and interpreted. Relation between onset dates of easterlies and northeast monsoon over Tamil Nadu has been examined. The normal date obtained has been shown to be by and large consistent with the characteristics of normal daily rainfall of coastal Tamil Nadu. The superposed epoch method has been, used to compute the mean rainfall with reference to onset date and the abrupt increase in rainfall at onset has been clearly brought out The spatial distribution and intensity of rainfall at the time of onset have also been discussed. Daily rainfall has been graphically presented for some years with spectacular onset as well as for some years with subdued onset.