SENSITIVITY OF UPPER OCEAN DYNAMICS IN HIGH-RESOLUTION TROPICAL INDIAN OCEAN MODEL TO DIFFERENT FLUX PARAMETERIZATION: CASE STUDY FOR THE BAY OF BENGAL (BOB)

Abstract

Simulation experiments using a high-resolution ocean general circulation model (OGCM) of the tropical Indian Ocean (TIO) were carried out to assess the model’s sensitivity to different flux parameterization. The flux formulation proposed by Kara et al. (2000) is used in the control run (CR). One more experiment differing in the bulk fluxes formulation for the computation of momentum, freshwater and heat is carried out. In the first experiment (CR), actual wind is used for the computation of the exchange coefficient in air-sea bulk flux formulation. In the second experiment (E1), model surface current is used in the wind stress formulation to compute the turbulent air-sea fluxes for TIO region. The formulation used in E1 is the same as it is used in CR, instead of actual wind, relative wind component is used in flux formulas. Both experiments are carried out for the period 2014–2016. The OGCM is forced using the daily fields of winds, radiation and freshwater fluxes obtained from ERA-Interim Reanalysis. In this study, we examine and quantify the performance of the above-mentioned experiments with respect to observations from ARGO, satellite-based sea surface temperature (SST) and sea surface salinity (SSS) for the year 2015. We observe that the upper ocean dynamics is significantly modulated by different flux algorithms. The errors in simulated SST is reduced by ∼8% to 10% in E1 compared to CR, respectively. The temperature errors in the top 20 m depth are reduced by 8% in E1. It is found that this flux formulation using relative winds is effective in accurately simulating the upper ocean dynamics in strong wind regimes of the Bay of Bengal.