"Oversampling Reflectivity Observations from a Geostationary Precipitation Radar Satellite: Impact to Typhoon Forecasts within a Perfect Model OSSE Framework"

The International Symposium on Data Assimilation Online (ISDA-Online) Feb 5, 2021
"Satellite Data Assimilation"
International Symposium on Data Assimilation - Online

For the past two decades, precipitation radars (PR) onboard low-orbiting satellites such as Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement (GPM) Core Observatory have provided valuable measurements of global precipitation and contributed to major advancements in weather and climate research. Building on this success, planning has begun on the next generation of satellite-based PR instruments, with the consideration for a future PR in geostationary orbit (GPR), bringing the advantage of quasi-continuous observations that would lead to new insights into global rainfall variability and improvement in numerical weather prediction through data assimilation.

Following the successful demonstration by a recent study to obtain three-dimensional (3D) precipitation data from a GPR, this study investigates the impact of GPR observations on analyses and forecasts for a West Pacific typhoon within a perfectmodel OSSE framework. 3D reflectivity observations are obtained for a GPR capable of achieving 20-km horizontal resolution at nadir with a range of beam sampling spans between 5-km and 20-km, following the finding that beam span is important in determining observation quality. Results showed improvement of the moisture field analyses for experiments assimilating observations with 5-km and 10-km beam sampling span compared to 20-km beam sampling (representing no-oversampling), with improved representation of key typhoon features, including the eye, eyewall and outer convective rainbands. Observations with finer beam sampling span resulted in improved minimum sea-level pressure error in forecasts at all lead times, while accumulated surface rainfall and maximum surface wind speeds forecasts also showed improvement when beam sampling span was reduced from 20-km to 5-km.