Validation and Impact of SCATSAT-1 Scatterometer Winds

Scatterometer winds are useful in weather forecasting and cyclone monitoring related activities. The Indian Space Research Organization has launched SCATSAT-1, which is a follow-up mission of the Oceansat-2 scatterometer in September 2016. It operates in the Ku-band frequency and provides wind vector data over oceanic region from sun synchronous polar orbit. SCATSAT-1 wind vector data are validated against buoy observations, other scatterometer observations and numerical weather prediction (NWP) analysis. It is found that SCATSAT observations are of good quality in comparison with other similar types of measurements. Impact of assimilation of these observations in NWP forecasts is investigated using the National Centre for Medium Range Weather Forecasting Global Forecast System (NGFS). The NGFS model employs a three-dimensional variational-ensemble Kalman filter (3D Var-EnKF) hybrid assimilation system with a deterministic model of T-1534 resolution and 80 member ensembles of T-574 resolution. Impact of assimilation of SCATSAT-1 observations in prediction of the Kyant, Nada and Varadha cyclones formed in the Bay of Bengal region and impact on operational forecasts are discussed. Assimilation of SCATSAT observations produced marginal improvement in general NWP forecast statistics and improvement is observed in cyclone track forecasts if observations are available near the cyclone position at analysis time.