Dipanjan Dey
PhD student at MISU

An assessment of TropFlux and NCEP air-sea fluxes on ROMS simulations over the Bay of Bengal region

Dipanjan Dey, PhD student at MISU.
Dipanjan Dey, PhD student at MISU.

The Bay of Bengal (BoB) is a unique basin in the North Indian Ocean (NIO) with SST above 28 °C , which is the threshold for active initiation of large-scale convection for most of the months in a year. In addition, the excess precipitation over evaporation and huge freshwater influx from the adjacent rivers make the upper surface features very stratified. Therefore, a careful selection of air-sea flux products for the ocean model simulations in this region is worth studying.

This study presents an assessment of the TropFlux and the National Centers for Environmental Prediction (NCEP) reanalysis air-sea fluxes in simulating the surface and subsurface oceanic parameters over the Bay of Bengal (BoB) region during 2002–2014 using the Regional Ocean Modelling System (ROMS). The simulated surface and subsurface temperatures in the TropFlux forced experiment (TropFlux-E) show better agreement with the Research Moored Array for African-Asian-Australian Monsoon Analysis (RAMA) and Argo observations than the NCEP forced experiment (NCEP-E). NCEP-E shows a limitation in simulating the observed seasonal cycle of the SST due to substantial underestimation of the pre-monsoon SST peak. These limitations are mostly due to the lower values of the NCEP net heat flux. The seasonal and interannual variations of SST in the TropFlux-E are better comparable to the observations with correlations and skills more than 0.80 and 0.90 respectively. However, SST is overestimated during summer monsoon periods mainly due to higher net heat flux. The superiority of TropFlux forcing over the NCEP reanalysis can also be seen when simulating the interannual variabilities of the magnitude and vertical extent of Wyrtki jets at two equatorial RAMA buoy locations. The simulated sea surface height anomalies (SSHA) from both the experiments are able to capture the regions of positive and negative SSHA with respect to satellite-derived altimeter data with better performance in the TropFlux-E. The speed of the westward propagating Rossby wave along 18°N in the TropFlux-E is found to be about 4.7 cm/s, which is close to the theoretical phase speed of Rossby waves.


Time and Place:
Thursday Sep 28th 2017, 14.15
Rossbysalen C609, Arrhenius Laboratory, 6th floor

(This event has taken place.)