Combined Polarimetric Doppler Radar and Satellite Scatterometer Observations of Organized Convection Near Coastal Regions

Satellite scatterometers (e.g., Advanced Scatterometer or ASCAT, RapidScat, etc.) are specialized radars that make routine measurements from space of near-surface, horizontal vector winds over the ocean. Organized convective storms can disrupt these measurements, via attenuation of the scatterometer signals by precipitation, as well as the creation of reflective surface capillary waves from raindrop impacts. However, coastal- and island-based polarimetric Doppler radars provide complementary measurements that can mitigate these impacts. For example, these radars can measure precipitation rates, vertically integrated liquid- and ice-water paths, particle size distributions, and particle type. This information can be used to assess the impact of precipitation on scatterometer measurements. In addition, via single- or multi-Doppler retrievals these radars can provide additional information about low-level winds, including their vertical profiles. Moreover, these radars can provide time-resolved information on convective storm morphology and evolution, which is crucial for understanding the contexts of successive scatterometer overpasses. On the other hand, scatterometers provide useful wind information on the outskirts of convective storms, including observations of cold pools in the clear air that surface-based radars often miss.

This presentation will report on ongoing work employing coastal/island radars and satellite scatterometers to study the evolution of organized convection near coastlines. One topic to be discussed is characterizing how well successive ASCAT-A and ASCAT-B overpasses (~50 min apart) resolve wind variability associated with convective evolution as described by the surface radars. In addition, differences in observations from C-band scatterometers like ASCAT, and Ku-band scatterometers like RapidScat, will be placed in context of longer-wavelength surface radar observations (i.e., S-band) that are less subject to attenuation. Combined analysis of ground radar wind/precipitation and L-band Cyclone Global Navigation Satellite System (CYGNSS) wind speed observations (which are not as subject to attenuation by rainfall) in near-shore convection also will be presented. Implications of the results for global observations of convectively driven winds from the available constellation of scatterometers will be summarized.