Role of Ocean Dynamics on Mesoscale and Sub-Mesoscale Variability of Ekman Pumping for the Bay of Bengal using SCATSAT-1 Forced Ocean Model Simulations

Role of ocean dynamics on vertical velocity of Ekman pumping (VVE) is analysed using simulations from very high resolution Ocean General Circulation Model (OGCM) configured for the Bay of Bengal (BoB). For this purpose, OGCM is forced with SCATSAT-1 scatterometer wind fields for 2017. Three mechanisms which modify VVE in the ocean are addressed in this study; the first results from the influence of sea surface temperature (SST) on wind field, and the other two arise from the influence of ocean surface currents (OSCs) on the wind field. Analysis for different length scales ranging from mesoscale to sub-mesoscale is also carried out. The results suggest a significant role of ocean dynamics on VVE, especially over submesoscale range (spatial scales of the order of 2– 10 km). Relative vorticity of OSC-induced Ekman pumping is found to be quite high (~3 m/day) at 2 km length scale, especially along the periphery of mesoscale eddies and along the filament structures. Impact of SST on VVE is least amongst the three factors and is observed to be significant only up to the length scales of 30 km. For length scales less than 10 km, relative vorticity-induced Ekman pumping increases drastically and the total Ekman pumping vertical velocity is predominantly controlled by the relative vorticity of OSC-induced Ekman pumping only.