Assimilation of GPM Retrieved Surface Meteorology Variables with ICE-POP Case Studies

As part of NASA's Weather Focus Area and GPM Ground Validation support of the International Collaborative Experiment for Pyeongchang 2018 Olympic and Paralympic Winter Games (ICE-POP 2018) program, near-real-time ocean surface flux retrievals were produced using the GPM microwave imager constellation. In the process of estimating surface turbulent fluxes, the GPM brightness temperature data also provided estimates of the ocean surface meteorology — specifically, wind speed, sea surface temperature (SST), air humidity and temperature information.

This research seeks the extended application of the GPM retrieved surface variables with data assimilation. Two snowfall events during the ICE-POP field campaign are selected to investigate the assimilation of the retrieved hourly temperature, moisture, wind speed, and SST data, and to specifically assess the impact of the retrieved data on precipitation forecasts. With collaboration of the NASA Short-term Prediction Research and Transition (SPoRT) Center, this research explores regional assimilation of the GPM derived product for winter storms.

The study methodology involves using the community NOAA Gridpoint Statistical Interpolation (GSI) v3.6 as developed by the Development Testbed Center (DTC). The GSI system was slightly modified to ingest the retrieval data, and was used to conduct the data assimilation experiments. Case studies for snowstorms in Japan on February 15 - 18 2018, and in Korea on February 27 - 28 2018 have been conducted using the regional Weather Research and Forecasting (WRF) model. The GPM retrieved surface temperature, humidity, wind and SST data was assimilated into 9, 3, and 1 km resolution WRF initial condition, followed by 24-h forecast. The control WRF model forecasts was compared with data assimilation experiments for statistic analysis on the impact of data assimilation on precipitation, temperature/humidity, and flow structure. Our presentation will focus on preliminary verification of the impact of derived data for the ICE-POP winter weather events.