Abstract
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.
Highlights
Momentum and heat flux exchange at the air-sea interface constitute key connector between the ocean and atmosphere and play a significant role in the circulation and the energy exchange between these two systems (Gill, 1982; Fairall et al, 1994, 1996a, 1996b, 2003; Kara et al, 2000; Siedler et al, 2013)
In ocean general circulation model (OGCM) simulations, turbulent air-sea fluxes (TASFs) are generally implemented either one of the three ways: i) using a prescribed fields that are generated from a climatological data set, atmospheric model (Kallberg, 1998), and remotely sensed and field observations (Cumming et al, 1997; Weller et al, 1998); ii) using bulk parametrizations that depend on the surface characteristic at the air-sea interface (e.g., heat fluxes (Hogan and Rosmond, 1991); and iii) using turbulence-based air-sea bulk flux formulations (Fairall et al, 1996a, 1996b, 2003)
We have investigated the impact of including model surface currents in the bulk formulas on air-sea fluxes and the ocean general circulation model using a high resolution standalone tropical Indian Ocean (TIO) model
Summary
Momentum and heat flux exchange at the air-sea interface constitute key connector between the ocean and atmosphere and play a significant role in the circulation and the energy exchange between these two systems (Gill, 1982; Fairall et al, 1994, 1996a, 1996b, 2003; Kara et al, 2000; Siedler et al, 2013). In ocean general circulation models (OGCMs), surface wind stress and the heat fluxes are the major driving forces that modify the upper ocean dynamics and thermodynamics (Yuen et al, 1992; Chen et al, 1994; Shriver and Hurlburt, 1997; Swenson and Hansen, 1999; Kara et al, 2000). The previous studies often rely on the sensitivity of North Pacific, North Atlantic and the Southern Ocean model simulations [e.g., Dawe and Thompson, 2006; Zhai and Greatbatch, 2007; Eden and Dietze, 2009; Munday and Zhai, 2015] to bulk flux algorithm.
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