Response of sea state to the monsoon onset

Utilizing the buoy meteorological data of Arabian Sea collected during the onset phase of ARMEX an attempt has been made to examine the influence of monsoon onset 2003 on the surface parameters. The peaking and collapse of warm pool during monsoon onset 2003 has been compared with the normal peaking and collapse conditions and it has been found that the collapse of warm pool during the onset of 2003 monsoon was very gradual. As a matter of fact the evaporative cooling in the warm pool region was quite subdued during 2003 monsoon onset which shows that the sudden collapse of warm pool should be expected to occur only when onset vortex is formed which did not happen during 2003.The roughness of sea (wave height) increased over the southeastern Arabian Sea about 2-3 days before the monsoon onset showing that the swells are reliable precursors of monsoon onset. There was a steep fall in SLP throughout the eastern Arabian Sea (8° - 20° N) about a week before the monsoon onset over Kerala on 8 June. All buoys from DS7 to SW1 registered this type of SLP change. After the sudden fall on 1 June the SLPs over the eastern Arabian Sea remained almost steady and unimpacted by the monsoon onset on 8 June or subsequent advance along the west coast.