Formation and spreading of Arabian Sea high-salinity water mass

The formation and seasonal spreading of the Arabian Sea High-Salinity Water (ASHSW) mass were studied based on the monthly mean climatology of tempera ture and salinity in the Arabian Sea, north of the equator and west of 80 d egrees E, on a 2 degrees x 2 degrees grid. The ASHSW forms in the northern Arabian Sea during winter and spreads southward along a 24 sigma-t surface against the prevailing weak zonal currents. The eastern extent of the core is limited by the strong northward coastal current flowing along the west c oast of India. During the southwest monsoon the northern part of the core s hoals under the influence of the Findlater Jet, while the southern part dee pens. Throughout the year the southward extent of the ASHSW is inhibited by the equatorial currents. The atmospheric forcing that leads to the formati on of ASHSW was delineated using the monthly mean climatology of heat and f reshwater fluxes. Monsoon winds dominate all the flux fields during summer (June-September), while latent heat release during the relative calm of the winter (November-February) monsoon, driven by cool, dry continental air fr om the north, results in an increased density of the surface layer. Thus ex cess evaporation over precipitation and turbulent heat loss exceeding the r adiative heat gain cool the surface waters of the northern Arabian Sea duri ng winter and drive convective formation of ASHSW.