Assessment of SCATSat‐1 Scatterometer Winds on the Upper Ocean Simulations in the North Indian Ocean

Abstract

AbstractThe performance of a new scatterometer SCATSat‐1 winds with TropFlux on simulating the upper oceanic processes is analyzed over the northern Indian Ocean (IO) using Regional Ocean Modeling System (ROMS). The nutrient, phytoplankton, zooplankton, and detritus (NPZD) ecosystem model are included for studying the postcyclonic responses on biophysical parameters during three cyclones of different intensities (Maarutha, Mora, and Ockhi) in 2017. The SCATSat‐1 (TropFlux) winds showed that skill scores are higher than 0.85 (0.66), and RMSEs are less than 0.48 (1.96) m s−1 with RAMA and OMNI buoy observations. Two SCATSat‐1 wind experiments, one with 1/4° (SS‐E) and other regridded wind to 1° (SSR‐E), are compared with the simulation by TropFlux air‐sea fluxes available at 1° (TF‐E). Seasonal variability of simulated oceanic parameters in SS‐E and SSR‐E showed marginal improvement than TF‐E as compared with observations. However, SSHA variability associated with downwelling Kelvin waves along the Bay of Bengal coast and southward east India coastal current (EICC) during postmonsoon is better simulated in SCATSat‐1 experiments. All experiments showed observed intraseasonal oscillations (30–90 days) with higher variability in thermocline than upper layers at RAMA locations over the equator. On western (eastern) equatorial IO, the signals are stronger during boreal winter (premonsoon) and summer (monsoon). Drop in temperature up to 2.5°C during cyclonic events is reasonably better captured in SS‐E and SSR‐E than TF‐E due to better accuracy in SCATSat‐1 winds. During cyclones, surface chlorophyll attained a peak after 5–10 days of cyclone passage in SCATSat‐1 winds experiments and satellite observations.