Latent heat flux variation during the warming phase of intraseasonal oscillations over northern Bay of Bengal

Abstract

The sensitivity of latent heat flux to the warming phase of intra-seasonal oscillation in the Bay of Bengal is studied with the help of in-situ data. This was analyzed from 2012 to 2015 with the help of data obtained from moored buoys deployed in the northern Bay of Bengal. The annual secondary peaks in sea surface temperature is observed in the northern Bay of Bengal associated with the warming phase of the intra-seasonal oscillation during southwest monsoon season, with net heat flux dominantly governing the mixed layer temperature. An increase in the release of latent heat flux from the northern bay is observed with the warming phase of intra-seasonal oscillation, which again leads to cooling of sea surface temperature. Higher latent heat flux release associated with the intra-seasonal warming phase during southwest monsoon season has intrigued us to study the sensitivity of latent heat flux with sea surface temperature. The sensitivity of gradient in saturation specific humidity is comparatively higher than the sensitivity of wind speed to sea surface temperature variations during southwest monsoon season. The gradient in sea–air saturation specific humidity is largely driven by saturation specific humidity of air (Qa) during both the seasons. However, the correlation of gradient in saturation specific humidity with surface saturation specific humidity is higher during southwest monsoon season compared to northeast monsoon season. Thus, the warming phase of sea surface temperature associated with intra-seasonal oscillation during southwest monsoon season always lead to an increase in latent heat flux release, favoured by high sensitivity of surface saturation specific humidity to variations in sea surface temperature.