Characterization of air–sea interaction processes over the Bay of Bengal during the winter phase of ICARB field experiment

As part of the winter phase of the Integrated Campaign for Aerosols, gases and Radiation Budget (W-ICARB), different meteorological parameters were collected through an Automatic Weather Station mounted onboard Oceanic Research Vessel Sagar Kanya for a period of 35 days spanning from 26th December 2008 to 29th January 2009 over the Bay of Bengal (BoB). The objectives of this research article are two folded: first – we make use of W-ICARB meteorological database for investigation of the diurnal variability in the air–sea interaction parameters by studying the frequency distribution of the time of occurrence of minima and maxima and second – we report the significance of North–South latitudinal gradient in meteorological parameters observed during the cruise period. A careful statistical analysis revealed a significant semi-diurnal variability in the mean sea level pressure with two minima occurring consecutively at 3 LT and 15 LT, whereas the two maxima were observed at 9 LT and 21 LT respectively. With the available database, we report a new variability index representing a quantitative measure of the diurnal variability in the air–sea interaction parameters. Analysis of the W-ICARB database indicates the diurnal variability in mean sea level pressure, wind speed, sensible and latent heat flux larger than 50%, while it was ranging from 28% to 40% for the sea surface temperature, air temperature, humidity and momentum flux. On an average, the estimates of sensible and latent heat flux were marginally higher than the earlier field experiment conducted over the BoB. During the cruise period, most of the surface layer meteorological observations barring wind speed showed a significant North–South latitudinal gradient which was not reflected in the estimates of air–sea interface fluxes.