Initial Results of Integrating GPM/IMERG Precipitation Data into Operational Forecasting Environments

The Global Precipitation Measurement (GPM) mission core satellite was launched in February 2014 with the goal of providing the next-generation, state-of-the-art global quantitative precipitation estimates (QPE). Taking advantage of an international constellation of satellites of opportunity, the Integrated Multi-satellitE Retrievals for GPM (IMERG) produces precipitation estimates in the range 60°N-S every half hour at 0.1° resolution. The IMERG precipitation is calibrated to the GPM Microwave Imager/Dual-frequency Precipitation Radar combined product to provide the best possible estimates. IMERG products are produced at three different latencies to accommodate the unique requirements of the various user bases. The “Early” run has a 6-hour latency (for flash flood monitoring, etc.), the “Late” run has a 16-hour latency (for drought monitoring, crop forecasting, etc.) and the “Final” run has a 3-month latency (for research). The “Early” and “Late” data begin in March 2015, and the “Final” data begin in March 2014.

To assist partner NOAA/National Weather Service (NWS) offices in precipitation forecasting, the NASA Short-term Prediction and Research Transition (SPoRT) project transitioned the calibrated IMERG rain rate product for a preliminary evaluation during summer 2015. The IMERG rain rate is accumulated at 1-, 3-, 6-, 12-, and 24-hour intervals for dissemination to NWS forecast offices. Three regions were targeted for this evaluation, each with a participating NWS Weather Forecast Office and River Forecast Center: Alaska/North Pacific, Southwestern U.S., and Southeastern U.S./Puerto Rico. These three regions offer widely-varying characteristics, limitations, and requirements regarding the use of precipitation data in forecast operations. To evaluate the utility of the IMERG data, forecasters are providing feedback on how the IMERG product is used in operations, including documentation of the product's perceived strengths and weaknesses. In addition to this qualitative forecaster feedback, the “Early” and “Late” IMERG products are inter-compared quantitatively to current operational QPE products (i.e., Stage IV and Multi-Radar Multi-Sensor [MRMS]) using NCAR's Model Evaluation Tools (MET) in combination with a SPoRT-developed scripting package for the MET software. This presentation will summarize the qualitative forecaster feedback, as well as the quantitative comparison of the IMERG “Early” and “Late” product against the operational Stage IV and MRMS QPE products.