The speed and some other features of the sea-breeze Front at Madras

Abstract

The speed with which the sea breeze advances inland at Madras under various meteorological conditions and Its dependence on the time of onset and depth of penetration are discussed in this paper, utilising the records for the year 1945 and 1946 of autographic instruments at three stations located at different distances from the coast. A velocity of 10-15 mph, a south southeasterly direction of the resultant wind, the months April to September and a time of onset during the early afternoon are favoured most by the sea breeze at Madras. The average speed of the sea- breeze front is found to be 37 mph. It is accelerated with depth of penetration inland independently of the wind speed. It varies with the hour of onset of the sea-breeze, being lowest during the epoch of maximum temperature. The variation of the ratio of the speed inland to that near the coast with time of onset and direction of the on-shore wind is investigated. The results are explained on t he basis of the temperature gradient and its variation with distance inland. The mean temperature drop and vapour pressure rise caused by the sea-breeze for different times of incidence and magnitudes of wind velocity in the various months have also been studied. The changes are maximum in the proximity of the epoch of maximum temperature and in the month of July in the year. The results of this study would help in anticipating with sufficient accuracy and sufficiently in advance for aviation needs the time of onset of the sea-breeze and the accompanying meteorological changes at the airfield at Meenambakkam given the time of incidence and the direction of the on shore wind earlier at a point closer to the coast.