1. First Tropical Cyclone Overflights by the Hurricane Imaging Radiometer (HIRAD) Chris Ruf 1, Sayak Biswas 2, Mark James 3, Linwood Jones 2, Tim Miller 3 1. University of Michigan 2. University of Central Florida 3. NASA Marshall Space Flight Center College of Engineering Department of Atmospheric, Oceanic & Space Sciences IGARSS 2011 Vancouver BC, CANADA 26 July 2011

2. 26 July 11Ruf et al., First HIRAD TC Overflights, IGARSS 20112 / 13 Outline The Hurricane Imaging Radiometer (HIRAD) is a new airborne microwave spectrometer designed to be an enhanced imaging version of the operational Stepped Frequency Microwave Radiometer (SFMR) that has been used operationally by NOAA for decades to retrieve surface winds under heavy precipitation Instrument development has been led by NASA Marshall Space Flight Center, The University of Central Florida and the University of Michigan First airborne science flights were conducted during the Genesis and Rapid Intensification Processes (GRIP) campaign in Fall 2010 “First light” results from overflights of Hurricanes Earl and Karl are reported here

3. 26 July 11Ruf et al., First HIRAD TC Overflights, IGARSS 20113 / 13 HIRAD Instrument Overview Interferometric Aperture Synthesis Radiometer Freq: 4, 5, 6 & 6.6 GHz H-pol @ EIA = ± 65° Spatial resolution: –2 km @ nadir –6 km @ edge of swath Swath = 3x A/C altitude –~ 60 km for GRIP Software beam steering –No moving parts

4. 26 July 11Ruf et al., First HIRAD TC Overflights, IGARSS 20114 / 13 HIRAD Instrument Block Diagram

5. 26 July 11Ruf et al., First HIRAD TC Overflights, IGARSS 20115 / 13 HIRAD Integration on WB-57 Aircraft

6. 26 July 11Ruf et al., First HIRAD TC Overflights, IGARSS 20116 / 13 Hurricane Earl Best Track and HIRAD 1 Sep. Overpass HIRAD overpass

7. 26 July 11Ruf et al., First HIRAD TC Overflights, IGARSS 20117 / 13 HIRAD flight Hurricane Earl Max Windspeed History

8. 26 July 11Ruf et al., First HIRAD TC Overflights, IGARSS 20118 / 13 Nearly Coincident HIRAD/WB-57 and SFMR/P-3 Overpasses of Earl on 1 Sep. Storm-centric coordinate system HIRAD/SFMR matchups TBs are expected to agree only at the nadir point.

9. 26 July 11Ruf et al., First HIRAD TC Overflights, IGARSS 20119 / 13 HIRAD TB Images at 4.0, 5.0 and 6.6 GHz along Northbound Earl Overpass 4.0 GHz5.0 GHz 6.6 GHz

10. 26 July 11Ruf et al., First HIRAD TC Overflights, IGARSS 201110 / 13 HIRAD Tb@ 4GHz HIRAD Tb@ 5GHz Model Tb@ 4GHz Model Tb@ 5GHz SFMR Wind +50 (m/s) SFMR Rain +50 (mm/hr) HIRAD/SFMR West Leg Overpass stop start SFMR Flt Dir “Model” data are Tb’s computed from SFMR wind & rain fields

11. 26 July 11Ruf et al., First HIRAD TC Overflights, IGARSS 201111 / 13 Hurricane Karl Best Track and 3 HIRAD Overpasses on 14, 16 & 17 Sep. Storm center location during HIRAD overpasses indicated by triangles

12. 26 July 11Ruf et al., First HIRAD TC Overflights, IGARSS 201112 / 13 HIRAD 5 GHz TB Image for Karl 16 Sep. Overpass Storm-centric Longitude (deg) Storm-centric Latitude (deg) Leg 8 Leg 10 Leg 6

13. 26 July 11Ruf et al., First HIRAD TC Overflights, IGARSS 201113 / 13 Summary HIRAD produces SFMR-like TB images over a wide (~3x altitude) cross track swath Initial TB calibration/validation is possible using nearly coincident SFMR overpasses Final instrument calibration and the development of off-nadir versions of SFMR windspeed and rain rate retrieval algorithms are currently underway Future participation in NASA’s Hurricane and Severe Storm Sentinal (HS3) Earth Venture-1 mission