Interpreting Simultaneous horizontal and vertical polarization transmit radar data collected during TiMREX

Presentation Type: 
John Hubbert (NCAR/EOL)

Radars that achieve dual-polarization by transmitting both horizontal and vertical polarization simultaneously (SHV) are becoming quite common. It is well know that cross-coupling of the H and V transmitted waves due to aligned canted ice crystals bias the polarimetric signatures. The bias is most evident in Zdr (differential reflectivity)as radial streaks in range of biased data. In 2008 during TiMREX (Terrain-influenced Monsoon Rainfall Experiment) in Taiwan, S-Pol (NCAR S-band dual polarized research radar) collected data both fast alternating H and V transmit (FHV) data as well as SHV data in close time proximity. This allows for a comparison of the FHV and SHV polarimetric signatures. The FHV data show radial streaks of LDR (Linear Depolarization Ratio) data in the same region where the radial SHV Zdr streaks are. Both are caused buy cross-coupling. Using Kdp (specific differential phase) and Zdr , it is inferred that two populations of ice particles simultaneously exist in the radar resolution volumes. T-matix scattering calculations support the inferences. Negative Kdp regions are shown where it is likely that an electric field vertically aligned the ice crystals. Dual-Doppler analysis as well as sounding data support the inferences.

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