Hurricane Imaging Radiometer (HIRAD) Observations in Hurricanes Patricia, Joaquin, and Marty (2015)

The Hurricane Imaging Radiometer (HIRAD) is designed to measure surface wind speeds in hurricanes, using retrieval concepts similar to those from the Stepped Frequency Microwave Radiometer (SFMR) but applied to a broad data swath. In 2015, HIRAD flew on a NASA WB-57 high-altitude aircraft as part of the Office of Naval Research Tropical Cyclone Intensity (TCI) experiment. The HIRAD observes a ~60 km wide swath from typical WB-57 altitudes (~20 km).

Highlights of the TCI campaign included:

- three science flights over Eastern Pacific Hurricane Patricia (a rapidly intensifying tropical storm on 21 October; a rapidly intensifying category four hurricane on 22 October; a weakening category five hurricane on 23 October)

- four science flights over Atlantic Hurricane Joaquin (a category three or four hurricane over the Bahamas on 2 October; a category four hurricane on 3 October; a weakening hurricane approaching and passing Bermuda on 4 and 5 October)

- two science flights over Eastern Pacific Hurricane Marty (as a tropical storm on 27 September and hurricane on 28 September).

TCI also included Yankee Environmental Systems' High Density Sounding System (HDSS) on the WB-57, with dropsondes released a few miles apart across the storms' inner cores. Several WB-57 flights had overlap with low-altitude reconnaissance or research flights conducted by the US Air Force Reserve (WC-130J) or NOAA (WP-3D).

Wind speed horizontal structure will be presented for these cases as derived from HIRAD, with comparisons to ancillary data from the HDSS dropsondes on the WB-57 and SFMR on the WC-130J and WP-3D aircraft.