Data Assimilation Seminar

Dr. James Taylor (May 1, 2020, 14:00-15:00)

Affiliation R-CCS
Title Oversampling Reflectivity Observations from a Geostationary Precipitation Radar Satellite: Impact on Typhoon Forecasts within an OSSE Framework
Abstract For the past two decades, Precipitation Radars (PR) onboard low-orbiting satellites such as Tropical Rainfall Measuring Mission (TRMM) have provided valuable measurements of global precipitation and contributed to advancements in weather and climate research. Building on this success, planning has now 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 obtaining observations at higher frequency. Following the successful demonstration by a recent study to obtain three-dimensional precipitation data from a GPR, this study investigates the impact of observations on analyses and forecasts for a West Pacific typhoon within an OSSE framework. Reflectivity observations are obtained for a range of beam sampling spans (20, 15, 10, 5km), following the finding that beam span is important for determining observation quality and reducing the impact of surface-clutter contamination. Results showed that with a 5-km and 10-km beam sampling span, the moisture field is improved in the analysis, enabling better representation of typhoon features, including the eye, eyewall and outer convective rainbands. Oversampling with increasingly finer beam sampling span resulted in smaller minimum sea-level pressure error in forecasts at all lead times. Forecasts of accumulated surface rainfall and maximum surface wind speeds were also found to be improved for the 5-km beam sampling case compared to no oversampling.

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