Frozen Precipitation Particle Properties Estimated from Dual-frequency Precipitation Radar and GPM Microwave Imager

抄録

 To estimate global frozen precipitation particle characteristics, this study developed a method that utilizes Global Precipitation Measurement (GPM) Dual-frequency Precipitation Radar (DPR) and GPM Microwave Imager (GMI) observations. This method estimates the volume-weighted mean diameter before melting (D_m) and the number concentration (N_w) of frozen precipitation particles for a given particle model from the DPR reflectivity factors (Z_e). The likelihood of this particle model is estimated using the difference between the brightness temperatures at 89 and 166 GHz calculated from this D_m and N_w (TB_c) and the GMI observation (TB_o) as a measure.

 Particle models representing snowflake, aggregate, strongly rimed aggregate, and graupel (sphere) were selected from existing scattering databases. Under idealized conditions, the TB_c computed from DPR Z_e was highly dependent on the particle model. In the OLYMPEX (December 3, 2015) case, the TB_c calculated from the observed DPR Z_e also depended on the particle model. The most likely particle models were spherical particles and strong rimed aggregates south of the Olympic Mountains and aggregates to the north. The D_m values for the most likely particle models had a smaller bias than the D_m values for each particle model when compared with the OLYMPEX airborne observations.