| Summary: | 碩士 === 國立中央大學 === 大氣科學學系 === 105 === Geographically, Taiwan is located at subtropics, snowfall rarely occurred on the low elevation except the mountains. However, January 23 to 24, 2016 northern Taiwan was affected by strong continental cold high pressure system, many low altitude areas observed solid hydrometeor particles.
In order to analyze and validate this snow event, National Central University C-POL dual-polarization radar and CWB laser-optical Particle Size Velocity (PARSIVEL) at Anbu station were employed to classify the type of solid hydrometeor particles.
Dual-Polarization radar provides both high spatial and temporal resolution. An obvious layer with high differential reflectivity ZDR and low cross-correlation coefficient ρHV at very low altitude was observed in vertical cross section as the precipitation type switched from stratiform rain to snow. Simultaneously, the terminal velocity of particles turned smaller and the numbers of aggregrate increased at Anbu parsivel station. The radar data analysis matched parsivel data in the course of melting level gradually approached ground. According to Atlas and Ulbrich (1977) present Z-R relationship and Locatelli and Hobbs (1974) found the best-fit curves between diameter and terminal velocity of particles, summarize a range of suitable snowfall formulas in Taiwan.
Through the comparison between preliminary data analysis and the documented statistical classification results of ice particles, according to Locatelli and Hobbs(1974), the particles was classified as Densely rimed dendrites type. Further, the NCAR fuzzy logic bulk-hydrometeor particle identification algorithm (PID) was applied to the radar data to get the three-dimensional distribution of particle types. Wet snow, light rain and graupel were detected as a result of PID at lowest level, these results conformed with the in situ observation at NCU and Anbu station.
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