Towards Direct Assimilation of ATMS Radiances in HWRF Using NCEP GSI

The direct use of microwave radiance data for hurricane structure analysis has been limited by the scattering and absorption from clouds and precipitation. It's very difficult to properly account for such scattering and absorption signal in the direct use of radiances in hurricane. The vertical temperature structure, especially in low to middle atmosphere, is coarse due to limited AMSU channels. However, things will change with the advent of ATMS observations. With its new design in scanning geometry and more channels in temperature and water absorption lines ATMS provides the atmospheric temperature profiles of all weather conditions which . Compared to AMSU-A, ATMS has an additional 51.75 GHz channel which is sensitive to the temperature at 900-850 hPa. Its scan width of 2503 km is wider than the 2200-km width of AMSU-Awhich results in nearly no gap between two neighboring orbits at equator. Its continuous scanning along- and cross-rack may result in 1) about a 31.6 km resolution at the nadir, and 2) significant oversampling in the atmosphere off the nadir that can be optimally used to enhance the spatial resolution and reduce the instrument noise. In this study, the uncertainties of forward radiative transfer model and its Jacobian model in presence of typical hydrometers in hurricane condition are evaluated firstly, then the quality control and bias correction and observation error estimation are conducted for hurricane. The assimilation experiments of ATMS data in HWRF using NCEP GSI showed that the use of ATMS data in hurricane analyses and forecasts is very promising.