Creating and Using Sensors That Tell Us about Precipitation (Invited Presentation) (Centennial)

Precipitation is deceptively simple to measure — just put a container in the back yard — and this was the only technology available until radar was discovered to be capable of sensing precipitation in the 1940’s, leading to quantitative estimates by the 1970’s. Meanwhile, satellite-based sensors started advancing. The first precipitation estimates from space repurposed the existing geosynchronous satellite infrared (GEO-IR) data, but purpose-built passive microwave (PMW) sensors soon became a reality. In 1987, the launch of the first Special Sensor Microwave/Imager on the Defense Meteorological Satellite Program F08 by the U.S. Department of Defense, and their decision to open the dataset to public use, created a boom in precipitation algorithms that continues to this day. Experimental work to create a global multi-satellite product by Global Precipitation Climatology Project, and then a “virtual constellation” of PMW sensors from satellite agencies around the globe by the NASA/JAXA Tropical Rainfall Measuring Mission (TRMM) and by NOAA/NWS Climate Prediction Center, resulted in a new generation of quasi-global multi-satellite precipitation estimates at increasingly fine time and space scales. TRMM and the NASA/JAXA Global Precipitation Measurement mission have hosted precipitation radars in space, providing critical new quasi-global information about 3-D precipitation structures and enabling improved calibration of the PMW constellation’s estimates. In parallel, GEO-IR estimates have continued to be developed, and the surface gauge data were found to be critical for anchoring the satellite-based estimates. Recently, terrestrial microwave links used in cell phone networks have proved useful for estimating local precipitation, and cooperation by the cell phone companies has started enabling this new source of precipitation estimates in selected regions.

The talk will briefly summarize the state of the art and provide a few representative samples, including the distinction between Climate Data Record and High Resolution Precipitation Product standards. It will end with remarks on some of the outstanding problems in the field, including making reliable estimates over snowy/icy surfaces and in regions of complex terrain, improving the estimate of precipitation system behavior between satellite overpasses, and maintaining the number of satellites required to give sufficiently frequent observations to support the quality expected of the datasets.