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. 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. 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. HIRAD Instrument Block Diagram 5. HIRAD Integration on WB-57 Aircraft 6. Hurricane Earl Best Trackand HIRAD 1 Sep. Overpass HIRAD overpass 7. Hurricane Earl Max Windspeed History HIRAD flight 8. Nearly Coincident HIRAD/WB-57 and SFMR/P-3Overpasses of Earl on 1 Sep. Storm-centric coordinate system

HIRAD/SFMR matchups

TBs are expected to agree only at the nadir point.

9. HIRAD TB Images at 4.0, 5.0 and 6.6 GHz along Northbound Earl Overpass 4.0 GHz 5.0 GHz 6.6 GHz 10. HIRAD/SFMR West Leg Overpass HIRAD Tb@ 4GHz HIRAD Tb@ 5GHz Model Tb@ 4GHz SFMR Wind +50 (m/s) SFMR Rain +50 (mm/hr) stop start SFMR Flt Dir Model data are Tb s computed from SFMR wind & rain fields Model Tb@ 5GHz 11. Hurricane Karl Best Trackand 3 HIRAD Overpasses on 14, 16 & 17 Sep. Storm center location during HIRAD overpasses indicated by triangles 12. 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. 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 NASAs Hurricane and Severe Storm Sentinal (HS3) Earth Venture-1 mission