On the vergence field in the north Indian Ocean

Abstract

The paper presents some of the results of investigation on the divergence and convergence of the surface waters in the North Indian Ocean, for different months of the year. The divergence is computed by a graphical method from the data on surface currents. The divergence pattern shows considerable seasonal and space variations. Several centres of strong divergence and convergence occur in the open ocean regions in the equatorial parts of the Indian Ocean throughout the year. But strong divergences and convergences also occur in nearshore regions during certain periods of the year; for example, on the east coast of India, a strong divergence occurs in the month of March. Similarly, on the Somali coast, strong divergences with central values exceeding 40 units (1 unit = 2 x 10 sup(-7) sec sup(-1)) often occur. The investigation shows that the monsoon months (June, July and August) are the months of intense divergence of surface currents in the North Indian Ocean. During this period, the central values of some of the divergences and convergences exceed 60 units. The intense divergence during the monsoon months may be ascribed to the strong monsoon winds over the area. The divergence field indicates that along the east coast of India, upwelling may be prevalent during the period January to August while sinking may be prevalent during the remaining period of the year. This is in agreement with the earlier findings by the authors and others on upwelling on the east coast of India as deduced from temperature structure, etc. Along the west coast of India, divergence is prevalent from January to May or June. Along the Somali coast, divergence is prevalent from March to August, indicating upwelling.