Hurricane Imaging Radiometer (HIRAD) 2014 and 2015 Observations

The Hurricane Imaging Radiometer (HIRAD) was designed to measure ocean surface wind speed across a wide swath in hurricanes. It is a 4-channel, C-band passive microwave radiometer using retrieval concepts similar to the Stepped Frequency Microwave Radiometer (SFMR), but applied across a swath +/- ~60° below an aircraft. This allows mapping much of the hurricane's surface wind field while needing only a few passes across or near the hurricane's center.

HIRAD flew on a NASA WB-57 high-altitude (~18 km) aircraft over Hurricane Gonzalo in 2014, and is on the same aircraft for the 2015 hurricane season. Surface wind speed retrievals have been generated for the three Hurricane Gonzalo flights (Oct. 15, 16, 17), and these will be presented. Some retrievals from 2015 hurricanes may be ready in time for the conference, though no hurricanes have been overflown at the time of abstract submission. Validation of the HIRAD retrievals has been limited by a scarcity of coincident observations. There may be opportunities for comparisons with dropsondes from the WB-57 in 2015, or possibly with SFMR and dropsondes from other aircraft in flights later this year. There is also a possibility of comparing HIRAD surface winds with vertical wind profiles retrieved from the High-altitude Imaging Wind and Rain Airborne Profiler (HIWRAP) that flew with HIRAD on the WB-57 for the Hurricane Gonzalo flights in 2014.