Impact of Microphysical Parameterizations on Satellite All-Sky Infrared Data Assimilation and Practical Predictability of Hurricane Harvey (2017)

Satellites provide the majority of observations of tropical cyclones (TCs) when they are over the open ocean. These observations are under-utilized in operational global and regional forecasting models as most of the cloudy and precipitation-affected observations are discarded. Recent works have shown that assimilating all-sky infrared (IR) radiances from geostationary satellites improves TC track, intensity, and rainfall forecasts. This study examines how two different cloud microphysical parametrization schemes impact all-sky IR radiance assimilation and subsequent forecasts of Hurricane Harvey. Because model hydrometeor fields that are used to simulate IR radiances are strongly constrained by the model microphysics scheme, Harvey's dynamic and thermodynamic structure become very different when changing the microphysics schemes, which also leads to changes in subsequent intensity forecasts. Sensitivity forecasts suggest that intensity forecast errors in this study are primarily controlled by uncertainties in initial conditions, which are influenced by microphysics schemes as they simulate model priors differently when assimilating all-sky IR radiance. On the other hand, the microphysics schemes used during the free forecasts generally have a smaller impact on Harvey's intensity forecast errors.