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![Page 1: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/1.jpg)
Response of active and passive microwave sensors to precipitation at mid- and high altitudes
Ralf Bennartz
University of Wisconsin
Atmospheric and Oceanic Sciences Department
![Page 2: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/2.jpg)
Outline
• Introduction
• Comparison of ground-based radar with satellite data
• Combined active and passive mw modeling approach for future sensors
• AMSU precipitation classification: 89 versus 150 GHz
• Conclusions and Outlook
![Page 3: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/3.jpg)
Passive microwave precipitation signal
• Emission signal from liquid precipitation: Most directly linked to surface precip, ocean only.
• Scattering signal from frozen precip-sized ice particles: Only indirectly linked to surface precipitation,
• Most directly linked to surface precipitation
• Over cold (water) surfaces only
• All types of surfaces• More indirect
![Page 4: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/4.jpg)
Observation geometry
Altitude of radar beam (elevation 0.5°):
@100km distance: 2.2 km
@200km distance: 5.2 km
273 K isothermal typically at 2-3 km
![Page 5: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/5.jpg)
ThunderstormGraupel
(Cold air outbreak)Frontal
precipitation
Radar reflectivity [dBz]
Different precipitation events
![Page 6: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/6.jpg)
Radar versus passive microwave precipitation estimate
ThunderstormGraupel
(Cold air outbreak)Frontal
precipitation
Bennartz and Michelson (in press, Int. J. Rem. Sens.)
![Page 7: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/7.jpg)
Simulating passive mw-response for current and future sensors and missions (AMSR, SSMIS,(E) GPM)
waterofconstant Dielectric
efficiency Extinction)/(
velocityfall Terminal)(
ondistributi size DropN(D)
DiameterDrop
)/()(extinction Volume
)(ZtyreflectiviRadar
)()(6
Rrate Rain
ext
K
DQ
DU
D
dDDQDN
dDDNK
dDDUDN
e
e
2
6
3
D
D
D
Bennartz and Petty, JAM, 2001
Bennartz and Bauer Radio Sci. In press
![Page 8: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/8.jpg)
Volume extinction at 85 GHz and 150 GHz
![Page 9: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/9.jpg)
To SSM/Iresolution
To TMIresolution
Every 2ndscanline
![Page 10: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/10.jpg)
85 GHz 150 GHz
150 GHz @ TMI-resolution85 GHz @ TMI-resolution
Graupel shower 85 & 150 GHz
![Page 11: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/11.jpg)
183-7 GHz 183-3 GHz
183-3 GHz @ TMI-resolution183-7 GHz @ TMI-resolution
Graupel shower 183-7 & 183-3 GHz
![Page 12: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/12.jpg)
Frontal Graupel shower
Intensive convection
85 GHz 16 25 45
150 GHz 28 44 42
183-7 GHz 8 22 18
183-3 GHz 4 7 6
Maximum brightness temperature depressions
![Page 13: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/13.jpg)
Sensitivity to surface emissivity
(very dry atmosphere wvp = 6 kg/m2)
![Page 14: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/14.jpg)
Sensitivity to surface emissivity
(moist atmosphere, wvp= 35 kg/m2)
![Page 15: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/15.jpg)
Sensitivity to surface emissivity
(high cloud liquid water path, wvp=20 kg/m2)
![Page 16: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/16.jpg)
High-latitude precipitation classification based on AMSU-data for nowcasting purposes
(see presentation A. Thoss)
Rain rate
Class 1: Precipitation-free 0.0 - 0.1 mm/h
Class 2: Risk for precipitation 0.1- 0.5 mm/h
Class 3: Light/moderate precipitation 0.5 - 5.0 mm/h
Class 4: Intensive precipitation 5.0 - ... mm/h
![Page 17: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/17.jpg)
RGB AVHRR ch3,4,5 PC product RGB:red: very lightgreen:light/moderateblue:intense
Radar compositedifferent projection!
NOAA15 overpass 13 September 2000, 05:48 UTC
![Page 18: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/18.jpg)
150 GHz versus 89 GHz scattering index (land)
Bennartz et al. (Met. Apps., 2002, 9, 177-189)
• 150 GHz enhances dynamic range of SI by a factor of 2
• About 15% of the precip free areas are falsely identified as raining at 89 GHz. This is reduced to 2.6% at 150 GHz.
![Page 19: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/19.jpg)
AQUA AMSR-E
![Page 20: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/20.jpg)
• Data coverage: August 2002-....
• AQUA AMSR-E/AMSU/HSB
• Latitude range 50 N -70 N
• Network of 25 radars
• Radar reflectivities every 15 minutes
• Gauge-adjusted rain rates every 15 minutes
• volume scans of Gotland radar
Combined active/passive dataset for high latitudes
(UW-Madison/SMHI)
![Page 21: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/21.jpg)
AMSR-ESSM/I
![Page 22: Response of active and passive microwave sensors to precipitation at mid- and high altitudes Ralf Bennartz University of Wisconsin Atmospheric and Oceanic.](https://reader035.fdocuments.net/reader035/viewer/2022070414/5697c00a1a28abf838cc7ce7/html5/thumbnails/22.jpg)
Conclusions
Scattering signal shows good correlation to rain rate,
Active+passive mw simulation tools in place and show good agreement with observations
However, sensitivity varies strongly with type of precipitation event
High frequencies (e.g. AMSU 150 GHz) show much better response than lower (AMSU 89 GHz). Sensitivity is about a factor of 1.5 to 2 better.
Sensitivity of scattering signal to variations in surface emissivity is only critical for very dry atmospheres
Collecting AQUA+radar data