The Impact of Assimilating Cloud Information from ABI on Hurricane and Local Severe Storm Forecasts

Hurricanes and the local severe storms (LSS) are fundamentally related to clouds. The development and distribution of clouds directly affects the structure and accuracy of weather systems. A large amount of satellite observations under cloudy skies is discarded due to the inaccuracy of the Radiative Transfer Model (RTM) in simulating the cloudy radiance into numerical weather prediction (NWP) models. In addition, assimilation of reflective solar band (RSB) radiances into NWP is still challenging. The assimilation of cloud products provides an optional approach for NWP to absorb satellite cloud information. In this research, the cloud water path (CWP) and cloud ice path (CIP) derived from Advanced Baseline Imager (ABI) measurements onboard the Geostationary Operational Environmental Satellite (GOES) -16 are assimilated into Weather Research and Forecasting (WRF) Model using Gridpoint Statistical Interpolation (GSI) data assimilation system. A constraint technique has been imposed to limit the innovation of the hydrometeors. This technique is applied to reduce the big differences of the hydrometeors between model background and observations, and to assure that cloud information can be assimilated smoothly and efficiently.

To assess the impact of CWP and CIP data on short-term regional numerical weather prediction, three parallel 3-hourly cycling data assimilation and forecasting experiments are carried out on Hurricane Irma (2017) and a LSS case. The conventional and satellite data from Global Telecommunication System (GTS), GOES-16 ABI radiances under clear skies, and the CWP/CIP observations derived from ABI cloudy skies are assimilated in the experiments. Different microphysics schemes are tested to find out the most suitable one for hydrometeors assimilation. The forecasts on hurricane track, intensity, structures and precipitation are used to analyze the impacts and added values of the CWP/CIP assimilation. The mechanism of analysis and forecast improvement from the assimilation of ABI CWP/CIP is also analyzed and understood.