Maresa Searls - April 13

Weather and Climate Systems

Assessing Precipitation Delineation Capabilities of Spaceborne Radars

Maresa Searls

Wednesday, April 13

03:00 PM

Online

Precipitation is a primary source of freshwater, is a component of multiple Earth cycles, and has important impacts from natural hazards. Knowing when, where, and how much precipitation is falling is crucial for understanding Earth’s global cycles, predicting natural hazards, and monitoring weather in a changing climate. Spaceborne radars uniquely measure, provide the finest depiction of, and give the most accurate estimate of precipitation globally from space, including over the oceans and over land where rain gauges and radars do not reach. The Global Precipitation Measurement (GPM) mission dual-frequency precipitation radar (DPR) is the successor to the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) and expands on its capabilities with a dual-frequency radar and expanded area of coverage into the midlatitudes. The consistent ability to detect various precipitation magnitudes across satellite missions is critical to the study of global precipitation over various time periods, from short-term to climatic time scales. The precipitation detection capabilities of spaceborne radars are characterized as functions of their observed reflectivity and the corresponding precipitation magnitude given by the independent reference Ground Validation Multi-Radar/Multi-Sensor (GV-MRMS) over CONUS. The Heidke Skill Score, a measure of delineation skill with respect to random chance, is computed as a function of reflectivity and precipitation rate thresholds to synthesize the capabilities of the spaceborne radars. This evaluation enables a finer depiction and interpretation of spaceborne radar capabilities than the bulk metrics widely used in the literature (e.g. mean relative error, correlation coefficient). Results reveal that skill is more sensitive to changes in the reference rain rate at lower rain rates and more sensitive to changes in the spaceborne radar reflectivity at higher rain rates. Comparisons between the TRMM PR, the Ku band radar of the GPM DPR (GPM KuPR), and GPM DPR have shown that the TRMM PR and GPM DPR best delineate moderate precipitation while the GPM KuPR is able to detect precipitation with low to moderate skill. Comparisons also show that, while both the TRMM PR and GPM DPR perform better than GPM KuPR, the TRMM PR performs better at lower reflectivity thresholds while the GPM DPR performs better at higher reflectivity thresholds. These results have implications for the detection and delineation of various precipitation magnitudes globally, from lighter precipitation to extremes.