Retrieve rain/drizzle size distribution using dual-frequency millimeter-wave radars

Description

Differential measurements from a dual-frequency millimeter-wave radar, i.e., the difference between measurements at the two frequencies, provide a rich suite of information about both cloud and rain properties. Differential reflectivity is proportional to cloud liquid water content (LWC) if non-Rayleigh effects are negligible. When large drizzle drops or rain present, differential reflectivity, combined with vertical velocity and Doppler width measurements, enables unambiguous separation of non-Rayleigh effects and attenuation effects. These differential measurements have the following advantages: (1) they do not require absolute radar calibration, (2) they do not depend on air motion, and (3) they do not depend on turbulence broadening. Thus, this dual-frequency approach can provide accurate (unbiased) retrieval of cloud and rain properties. This approach is tested using observations from the Ka- and W-band cloud radars operated by the Atmospheric Radiation Measurement (ARM) Climate Research Facility.