The Influence of Barometric Pressure on the Specific Gravity of the Surface Water in Indian Seas

Abstract

IT has for many years been recognised that any alteration in barometric pressure over a wide expanse of water produces concomitant changes in the surface level, and Prof. J. W. Gregory (Scottish Geographical Magazine, 1909, vol. xxv. p. 316), when discussing the level of the sea, pointed out that “the sea in an area beneath high air pressure has its surface pushed downwards and the displaced water rises in the adjacent areas.” Since the waves of increased barometric pressure occur at approximately the same time of day in each degree of longitude, it follows that each succeeding elevation and depression of the surface level of the sea travels across the ocean like a wave from east to west. In the region of India the barometric pressure normally exhibits in every twenty-four hours a double rise and fall with maxima at approximately 9.45 A.M. and 10.30 P.M. and minima at 3.30 A.M. and 4.30 P.M.