Impact of wind forcing in a nested Indian Ocean regional model
摘要
Bulk formulas are used to estimate the turbulent surface fluxes (heat and momentum) over global oceans for weather forecasting, climate models, and ocean models. These formulas parameterize turbulent fluxes using near-surface atmosphere and ocean state variables. This turbulent flux computation introduces significant errors due to the errors in input meteorological variables used in bulk algorithms apart from the algorithm types. Stand-alone forced ocean models also use near-surface atmospheric variables from reanalysis or corrected reanalysis products. Sea Surface Temperature (SST) is influenced by air-sea flux exchange and mostly by net heat flux over the north Indian Ocean. Accurate computation of turbulent flux is needed to capture the realistic seasonal, intra-seasonal, and inter-annual SST variations in ocean model simulations. This study evaluates the impact of near-surface wind forcing in SST and current simulation in a nested regional Indian Ocean model. Two experiments were performed, in the control experiment, Coordinated Ocean-Ice Reference Experiments version II (CORE-II) inter-annual atmospheric forcing fields were used for the regional model simulations. The other experiment is the same as the control experiment, except the near-surface wind fields is used from the QuikSCAT satellite by replacing CORE-II winds. Four years of simulations (2003–2006) were performed for both the experiments. These simulations were evaluated using in-situ and satellite observations. The results show significant improvements in temperature and surface current simulations with QuikSCAT forcing compared to CORE-II forcing. These improvements in QuikSCAT simulations were due to improvements in the heat fluxes and mixed layer depth when compared with observations. Notable reductions in root mean square error for the surface current simulations are seen over the equatorial Indian Ocean.