Characteristics of atmospheric forcing and SST cooling events in the Gulf of Mannar during winter monsoon

This work addresses the analysis of winter monsoon forcing and sea surface temperature (SST) cooling events in the Gulf of Mannar, which is situated b etween the southeast of the Indian tip and northwest of Sri Lanka, using a 7-year data set derived from satellite sensors. The surface forcing consist s of wind stress and turbulent heat flux, which were estimated through the TOGA/COARE algorithm using Special Sensor Microwave Imager (SSM/I) wind, Ad vanced Very High Resolution Radiometer (AVHRR) SST, and surface atmospheric conditions derived from National Centers for Environmental Prediction/Nati onal Center for Atmospheric Research (NCEP/NCAR) reanalyses data. Net heat flux was derived by combining the turbulent heat flux with net short- and l ong-wave radiation from the NCEP/NCAR reanalysis data set. SST cooling was monitored by using 9-km spatial resolution pathfinder SST that was derived from the AVHRR. The 7-year weekly mean maps of wind stress, net heat flux, and SST indicate that SST cooling is locally influenced by surface forcing in- and offshore of the Gulf of Mannar. A time series of these parameters n ear the Indian tip reveal that the strong wind stress and high surface heat loss, which are punctuated in time varying from 15 days to more than a mon th, occur every winter and lower SST by similar to1.5 degreesC. The occurre nce of such a phenomenon is referred to as an event in this work. The bell- shaped events, which have a periodicity, of 15 days with a maximum wind str ess around Day 8, occur every winter and are characterized by the SST cooli ng of less than a degree. The features of these events are studied by using the statistical correlation and composite technique. It is inferred that t he SST cooling is strongly correlated with the surface forcing. (C) 2001 El sevier Science Inc, All rights reserved.