Instrument: Cloud Radar System (CRS)

Description
The Cloud Radar System (CRS) is a 94 GHz, W-band polarimetric Doppler radar designed to operate aboard the NASA ER-2 high-altitude research aircraft or as a ground-based radar. Its very high frequency and short 3 mm wavelength make it very sensitive; perfect for cirrus cloud studies in particular as it has the ability to collect more detailed cloud and precipitation observations than traditional weather radars. Since CRS was specifically tailored to operate from the NASA ER-2 aircraft, the instrument is compact, does not require pilot operation, and can capture measurements useful for the validation of satellite estimates. The CRS is housed inside the tailcone of either ER-2 superpod, located in the mid-sections of the aircraft wings. Because the ER-2 flies at a 20 km altitude, within the lower stratosphere, CRS in located in close proximity with its targets, decreasing measurement effects that would occur at a larger distance. It can detect clouds and precipitation from flight level down to the surface. When CRS is operating airborne, its downward pointing beam takes profiles of radar reflectivity and Doppler velocity. Its polarimetric capabilities enable it to measure the horizontal and vertical dimensions of cloud and precipitation particles, revealing cloud microphysical properties and processes. The CRS can also effectively detect the intense signal returned by the ocean’s surface, making the ocean an ideal target for calibrating the instrument. The specialized capabilities of CRS make it very useful for observing cloud microphysics and dynamics. Observations by CRS and other instruments mounted on the ER-2 aircraft also provide important insight into cloud radiative properties impacting Earth’s global energy budget.
Measurements

Measures radar reflectivity, Doppler velocity, linear depolarization ratio, and differential reflectivity. The Doppler velocity values are corrected for the motion and orientation of the aircraft. CRS has two operation modes. When CRS operates in ER-2 mode, it can measure reflectivity, Doppler velocity, and linear depolarization ratio. When it operates in ground-based mode, it can operate with full polarimetric capabilities.

Applications
Cloud and Precipitation Studies
Cloud Microphysics and Dynamics
Climate
Global Energy Budget
SENSITIVITY ANTENNA BEAM WIDTH PEAK POWER RANGE RESOLUTION FREQUENCY/WAVELENGTH PULSE REPETITION FREQUENCY (PRF)

-29 dBZe (airborne) and -46.9 dBZe (ground-based) at 10 km range

0.6 x 0.8 degrees (airborne) and 0.3 (ground-based) 1.7 kW 150 m at 10 km range

94.155 GHz

3 mm wavelength, W-band

0.5 - 20 kHz

 

Relevant Publications

Evans, K. F., Wang, J. R., Racette, P. E., Heymsfield, G., & Li, L. (2005). Ice Cloud Retrievals and Analysis with the Compact Scanning Submillimeter Imaging Radiometer and the Cloud Radar System during CRYSTAL FACE. Journal of Applied Meteorology, 44(6), 839–859. https://doi.org/10.1175/JAM2250.1

Li, L., Heymsfield, G. M., Racette, P. E., Tian, L., & Zenker, E. (2004). A 94-GHz Cloud Radar System on a NASA High-Altitude ER-2 Aircraft. Journal of Atmospheric and Oceanic Technology, 21(9), 1378–1388. https://doi.org/10.1175/1520-0426(2004)021%3C1378:AGCRSO%3E2.0.CO;2

Li, L., Heymsfield, G. M., Tian, L., & Racette, P. E. (2005). Measurements of Ocean Surface Backscattering Using an Airborne 94-GHz Cloud Radar—Implication for Calibration of Airborne and Spaceborne W-Band Radars. Journal of Atmospheric and Oceanic Technology, 22(7), 1033–1045. https://doi.org/10.1175/JTECH1722.1

McGill, M. J., Li, L., Hart, W. D., Heymsfield, G. M., Hlavka, D. L., Racette, P. E., … Winker, D. M. (2004). Combined lidar-radar remote sensing: Initial results from CRYSTAL-FACE. Journal of Geophysical Research, 109(D7), D07203. https://doi.org/10.1029/2003JD004030

Mitrescu, C., Haynes, J. M., Stephens, G. L., Miller, S. D., Heymsfield, G. M., & McGill, M. J. (2005). Cirrus cloud optical, microphysical, and radiative properties observed during the CRYSTAL-FACE experiment: A lidar-radar retrieval system. Journal of Geophysical Research, 110(D9), D09208. https://doi.org/10.1029/2004JD005605

NASA Airborne Science Program (2019). Cloud Radar System (CRS). https://airbornescience.nasa.gov/instrument/CRS

NASA Goddard Space Flight Center (2018). Cloud Radar System (CRS).
https://har.gsfc.nasa.gov/index.php?section=28

Wang, Z., Heymsfield, G. M., Li, L., & Heymsfield, A. J. (2005). Retrieving optically thick ice cloud microphysical properties by using airborne dual-wavelength radar measurements. Journal of Geophysical Research, 110(D19), D19201. https://doi.org/10.1029/2005JD005969

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