Biswas, Sayak Krishna

Cecil, Daniel Joseph

Jones, W. Linwood

NASA Technical Reports Server

Hurricane Imaging Radiometer 
(HIRAD)
Daniel J. Cecil, NASA Marshall Space Flight Center
Sayak K. Biswas, Universities Space Research Association
W. Linwood Jones, University of Central Florida
Daniel.J.Cecil@nasa.gov
https://ntrs.nasa.gov/search.jsp?R=20150004150 2019-08-31T11:16:24+00:00Z
HIRAD BackgroundC-band (4, 5, 6, 6.6 GHz) 
radiometer
Retrieval concept similar to 
the operational Stepped 
Frequency Microwave 
Radiometer (SFMR)
Retrieve Wind Speed and 
Rain Rate over ocean, but 
over a wide swath
C-band frequencies have 
varying sensitivity to rain but 
~equal sensitivity to wind 
speed (emission from foam 
on wind-roughened ocean 
surface)
0 200 400 600 800 1000 1200
90
100
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0 200 400 600 800 1000 1200
0
5
10
15
20
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HIRAD Tb
Tb7
Tb6
Tb5
HIRAD RetrievalsWS
RR
Hurricane Karl (2010) example
HIRAD Science Flights
Pre- TS Gabrielle 2013
Hurricane Gonzalo 2014 
(3 flights)
Hurricane Earl 2010
Hurricane Karl 2010
Hurricane Ingrid 2013
Hurricane Gonzalo (2014)
Oct 15 Oct 16 Oct 17
Storm motion not subtracted from these images
Flown on NASA WB-57 based out of Houston, forward-deployed to Tampa
Cooperation between NASA HS3 program and ONR TCI program
Instruments were integrated onto Global Hawk AV-1 in July for HS3, but
AV-1 was unable to perform missions. WB-57 was available for
hurricane flights because of the ONR program, so HIRAD and HIWRAP
were moved from Global Hawk to WB-57. Kudos to all who made this
switch possible!
First Storm Center Crossing: 20:34 UTC
5
0 0.5 1
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0.1
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0.3
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0.5
0.6
0.7
0.8
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1
 
 
0
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WS
(m/s)
SFMR center Crossing 
Time : 14:43 UTC
GOES Cloud Image @ 18:15 UTC 
Retrievals here use 3 HIRAD 
channels – 5, 6, 6.6 GHz
Geophysical model based on 
El-Nimri et al. (2010), 
Uhlhorn et al. (2007), 
Uhlhorn and Black (2003)
Second Storm Center Crossing: 21:12 UTC
6
0 0.5 1
0
0.1
0.2
0.3
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0.5
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1
 
 
0
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20
30
40
50
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WS
(m/s)
GOES Cloud Image @ 18:15 UTC 
SFMR center Crossing 
Time : 14:43 UTC
Retrievals here use 3 HIRAD 
channels – 5, 6, 6.6 GHz
Geophysical model based on 
El-Nimri et al. (2010), 
Uhlhorn et al. (2007), 
Uhlhorn and Black (2003)
Wind Retrievals – Oct 15 Gonzalo
20:34 UTC
HIRAD
21:12 UTC
HIRAD
14:43UTC
SFMR
HIRAD has biases at some 
incidence angles, seen as 
along-track striping.
Also tends to be high-biased 
along left edge.
Work in progress
Retrievals here use 3 HIRAD 
channels – 5, 6, 6.6 GHz
Geophysical model based on 
El-Nimri et al. (2010), 
Uhlhorn et al. (2007), 
Uhlhorn and Black (2003)
First Storm Center Crossing: 14:04 UTC
8
0 0.5 1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
 
 
0
10
20
30
40
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WS
(m/s)
HIRAD: 13:53 UTC
HIRAD: 14:15 UTC
SFMR: 11:24 UTC
SFMR: 12:03 UTC
SFMR: 12:32 UTC
SFMR: 13:21 UTC
SFMR: 13:57 UTC
SFMR: 14:15 UTC
SFMR: 14:40 UTC
SFMR: 16:13 UTC
GOES Cloud Image @ 12:15 UTC 
Concentric eyewalls, with 
Northern Inner Eyewall and 
Western Outer Eyewall
appearing strongest
Second Storm Center Crossing: 14:41 UTC
9
0 0.5 1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
 
 
0
10
20
30
40
50
60
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WS
(m/s)
HIRAD: 13:53 UTC
HIRAD: 14:15 UTC
HIRAD: 14:32 UTC
HIRAD: 15:54 UTC
GOES Cloud Image @ 12:15 UTC 
Concentric eyewalls, with 
Northern Inner Eyewall and 
Western Outer Eyewall
appearing strongest
SFMR: 11:24 UTC
SFMR: 12:03 UTC
SFMR: 12:32 UTC
SFMR: 13:21 UTC
SFMR: 13:57 UTC
SFMR: 14:15 UTC
SFMR: 14:40 UTC
SFMR: 16:13 UTC
Wind Retrievals – Oct 17 Gonzalo
Hurricane Karl (2010)  Brightness Temp 
and Wind Speed Retrieval
6.6 GHz TB
Surface Wind 
Speed
HIRAD Wind Retrieval, Assimilation for Hurricane Karl
HIWRAP VAD wind 
assimilated
HIRAD surface wind 
and HIWRAP VAD wind 
assimilated
HIRAD surface wind, dropsonde
wind,  and HIWRAP VAD wind 
assimilated
Surface wind field in data assimilation experiments from Jason Sippel at GSFC
Adding HIRAD (bottom middle) improves characterization of asymmetric nature of 
wind field, and correctly reduces the horizontal extent of the wind field. Control and 
Control+HIWRAP(radar) experiments had Radii of 50-kt and 34-kt winds too large, 
compared to Best Track
Best results from assimilating Dropsonde, HIRAD, HIWRAP together
Summary
• 3 Science Flights from WB-57 over Hurricane Gonzalo (2014)
• Wide-swath data helps
paint a picture of hurricane structure
• Initial retrievals from Oct 15, Oct 17
flights look good, some systematic
(scan-angle dependent) biases remaining
• Oct 16 data needs more cleanup before retrievals, but 
hurricane structure is there
• Hurricane Karl (2010) wind retrievals tested in assimilation 
with dropsondes and HIWRAP; improved structure of wind 
radii  


Hurricane Imaging Radiometer (HIRAD)

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