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Remote detection of cloud phase in either liquid, ice or mixed form a key microphysical observation. Evolution of a cloud system and associated radiative properties depend on microphysical characteristics. Polarization radars rely on the shape of the particle to delineate the regions of liquid and ice. For specified transmitter and receiver characteristics, it is easier to detect a high concentrations of larger atmospheric particles than a low concentration of small particles. However, the radar cross-section of a given hydrometeor increases as the transmit frequency of the radar increases. Thus, in spite of a low transmit power, the sensitivity of a millimeter-wave radar might be better than high powered centimeter-wave radars. Also, ground clutter echoes and receiver system noise powers are sensitive functions of radar transmit frequency. For example, ground clutter in centimeter-wave radar sample volumes might mask non-precipitating or lightly precipitating clouds. An optimal clutter filter or signal processing technique can be used to suppress clutter masking its effects and/or enhanced weak cloud echoes that have significantly different Doppler characteristics than stationary ground targets. In practice, it is imperative to investigate the actual performance of S and Ka-band radar systems to detect small-scale, weak cloud reflectivity. This paper describes radar characteristics and the sensitivity of the new system in non-precipitating conditions.
Recently, a dual-wavelength S and Ka-band radar system with matched resolution volume and sensitivity was built to remotely detect supercooled liquid droplets. The detection of liquid water content was based on the fact that the shorter of the two wavelengths is more strongly attenuated by liquid water. The radar system was deployed during the Winter Icing Storms Project 2004 (WISP04) near Boulder, Colorado to detect and estimate liquid water content. Observations by dual-wavelength radar were collected in both non-precipitating and lightly precipitating clouds.
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