Measurement Method for Specific Attenuation in the Melting Layer Using a Dual Ka-Band Radar System

An estimation method for specific attenuation and equivalent radar reflectivity in the melting layer using a dual Ka-band radar system was studied. The system consists of two identically designed Ka-radars. When a precipitation system comes between the two radars, the radars observe the system from opposite directions. The radar applies the frequency-modulated continuous-wave type and is designed for the measurement of the scattering characteristics of precipitation particles. The precipitation echoes suffer from rain attenuation. The reduction due to rain attenuation symmetrically appears in both radar echoes. By differentiating averaged measured radar reflectivity with range, the specific attenuation can be estimated. After obtaining the specific attenuation, equivalent radar reflectivity is estimated. In the melting layer, specific attenuation and the equivalent radar reflectivity vary largely along the radio path, and the estimated specific attenuation is very sensitive to the setup configuration of the experiment. The accuracy of the estimated specific attenuation was found to depend on the curvature, that is, the doubly differentiated value of the equivalent radar reflectivity with respect to range and the distance for the differentiation. The measurement system and actual procedure for the data analysis are also described.