Estimation of Geotropic Currents in the Bay of Bengal using In-situ Observations.

Abstract:

Geostraphic Currents (GCs) can be estimated from temperature and salinity observations. In this study an attempt has been made to compute GC using temperature and salinity observations from Expendable Bathy Thermograph (XBT) and CTD over Bay of Bengal (BoB). Although in recent time we have Argo observations but it is for a limited period and coarse temporal resolutions. In BoB Bengal, where not enough simultaneous hydrographic temperature and salinity data are available with reasonable spatial resolution (~one degree spatial resolution) and for a longer period. To overcome the limitations of GC computed from XBT profiles, temperature-salinity relationships were used from simultaneous temperature and salinity observations. We have demonstrated that GCs can be computed with an accuracy of less than 8.5 cm/s (root mean square error) at the surface with respect to temperature from XBT and salinity from climatological record. This error reduces with increasing depth. Finally, we demonstrated the application of this approach to study the temporal variation of the GCs during 1992 to 2012 along an XBT transect.