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Comparison of High-Altitude Remote Aircraft Measurements with the Radar Structure of an Oklahoma Thunderstorm: Implications for Precipitation Estimation from Space

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  • 1 Laboratory for Atmospheres, NASA, Goddard Space Flight Center, Greenbelt, Maryland
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Abstract

Observations of an isolated group of Oklahoma thunderstorms from NASA's high altitude ER-2 aircraft are presented. These observations include passive radiometric measurements at frequencies in the microwave (92, 183 GHz), infrared (10.7 μm) and visible portion of the spectrum from a perspective above the storm top. Direct measurements of cloud top height were also collected using a pulsed lidar instrument. These remote observations are discussed and compared with coincident radar data from the National Severe Storms Laboratory's two Doppler radars and in situ cloud top particle data from the University of North Dakota's Citation aircraft.

Reflectivity cores are nearly colocated with cold anomalies in the microwave brightness temperature field. Coldest infrared brightness temperatures however, are displaced downshear of the convective region in association with the cirrus anvil. Radar and in situ microphysical comparisons support previous theoretical and numerical modeling results which suggest that microwave frequencies are sensitive to the deeper layer of large ice particles in the storm's convective region. The trailing anvil which is comprised of smaller ice particles is transparent at 92 GHz and nearly transparent at 183 GHz. This observation has relevance to spaceborne passive microwave measurements of rainfall.

Evolution of the thunderstorm complex is also discussed. The trend of the radar volumetric rain rate correlates well with the trends of minimum 92 GHz brightness temperature and area of the cold brightness temperature region at 92 GHz. The correlation at 183 GHz as well as at the infrared wavelength is not nearly as clear.

Abstract

Observations of an isolated group of Oklahoma thunderstorms from NASA's high altitude ER-2 aircraft are presented. These observations include passive radiometric measurements at frequencies in the microwave (92, 183 GHz), infrared (10.7 μm) and visible portion of the spectrum from a perspective above the storm top. Direct measurements of cloud top height were also collected using a pulsed lidar instrument. These remote observations are discussed and compared with coincident radar data from the National Severe Storms Laboratory's two Doppler radars and in situ cloud top particle data from the University of North Dakota's Citation aircraft.

Reflectivity cores are nearly colocated with cold anomalies in the microwave brightness temperature field. Coldest infrared brightness temperatures however, are displaced downshear of the convective region in association with the cirrus anvil. Radar and in situ microphysical comparisons support previous theoretical and numerical modeling results which suggest that microwave frequencies are sensitive to the deeper layer of large ice particles in the storm's convective region. The trailing anvil which is comprised of smaller ice particles is transparent at 92 GHz and nearly transparent at 183 GHz. This observation has relevance to spaceborne passive microwave measurements of rainfall.

Evolution of the thunderstorm complex is also discussed. The trend of the radar volumetric rain rate correlates well with the trends of minimum 92 GHz brightness temperature and area of the cold brightness temperature region at 92 GHz. The correlation at 183 GHz as well as at the infrared wavelength is not nearly as clear.

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