Seasonal variation of some physical features of the coastal waters off Waltair

Abstract

The seasonal variation of temperature, density and transparency of the coastal waters off Waltair has been studied with the help of the data obtained on the oceanographic cruises of the Andhra University. The study reveal the following results. The surface temperature is lowest in December and highest in September. The annual range of temperature is not maximum at the surface but at some depth. In the surface layers, positive temperature gradients occur during the winter months and negative gradients during the remaining period of the year. The thermocline gets deeper and deeper during the period September to January and it begins to move up in February. The water undergoes large seasonal change of density at the surface with low values in October and high values in Spring and Summer. The annual range of density decreases with depth in the top fifty meters. The vertical density gradients in the surface layers are small in Spring and Summer and large in the Fall season. The transparency of the waters changes with season and distance from the coast. The nearshore waters are less transparent than those offshore, throughout the year. The most turbid waters for the year are encountered in April and Maya feature related to upwelling near the coast. Sinking during the period September to December and upwelling in Spring and Summer take place in nearshore regions.