Trends and Variability of Air Sea Turbulent Heat Fluxes in The North Indian Ocean

Abstract

Turbulent heat fluxes mainly include latent and sensible heat flux, which are two important components of the total heat budget as well. Among these two, latent heat flux (LHF) dominates over sensible heat flux (SHF) due to its large amplitude of variation. Previous studies found the North Indian Ocean (NIO) to exhibit unique variations in heat fluxes as compared to other ocean basins and hence was chosen as the study area. The turbulent heat flux variability at hourly, seasonal and climatological scales were analysed. Observations from moored buoys in the NIO as well as daily gridded objectively analyzed OA Flux data sets were used for the analysis. Hourly met-ocean parameters (wind speed (WS), relative humidity (RH), sea surface temperature (SST), air temperature (AT), and pressure) were utilized for estimating the turbulent heat fluxes. The state-of-art COARE 3.5 algorithm was used throughout the work to estimate LHF and SHF. newlineFirst, the sensitivity of the COARE model to various met-ocean parameters for estimating the LHF and SHF was carried out. Both the flux components were found to be most sensitive to variations in SST and least sensitive to the RH in the study region. Larger uncertanities in the LHF estimations were observed on using high resolution SST at 1 m and 5 m depth. By comparing the LHF by using SST at 1 m and 5 m depths. However, such uncertanities (greater than the established model uncertainty of ±10 W/m2) was observed only in 5.7% of the high resolution data sets. Further, all such cases were during the day time which was owing to the impact of the diurnal warm layer in the ocean. It was also concluded that uncertainity in the COARE flux estimations was less when WS above 5 m/s were provided as input. newline