Large eddy simulation of the combined effect of heat fluxes and wave forcing of summer monsoon on a diurnal ocean mixed layer in the north Arabian Sea

Abstract

Formation of a diurnal ocean mixed layer (OML) as one of the nonlinear dynamic processes has been investigated by using large eddy simulation (LES) in previous studies, but the effect of different terms of heat fluxes on the OML has not been discussed separately so far. In this paper, the effect of air–sea interaction on the OML was evaluated by large eddy simulation (LES) in the presence or absence of Langmuir circulation (LC), wave breaking (WB), sensible heat flux (SHF), long wave radiation (LWR), latent heat flux, and insolation or short wave radiation for the first time. We used average climatic parameters for the Arabian Sea during the summer monsoon to define the ideal case of simulation. The area was simulated for 33.5 h, and the results of the first 9.5 h were ignored. The variation of different simulated parameters was investigated during a 24-h period. The results of the present study showed that since the SHF and LWR values were omissible, the effects of these two fluxes on many OMD properties are negligible. We also observed that SHF had a reversible effect because of its positive and negative values during the defined timeframe of the simulation. In addition, the maximum impression of heat fluxes was seen in the presence of evaporation and insolation. However, the evaporation in the absence of LC and WB caused a slight decrease in velocity shear and shear production and an increase in the dissipation rate (approximately double), pressure transport, and TKE transport. Moreover, in the presence of evaporation, the presence or absence of LC and WB did not affect the profile of turbulent heat flux. Evaporation did not change the Stokes production as well. The results of this study show that the effect of solar insolation on OML is significant and even more effective than surface evaporation. It reduced TKE and causes most of the diurnal variation in TKE. Furthermore, significant changes in the TKE profile are controlled by the shear production profile.