Observational Analysis of X-band Dual-Polarization Radar for Beijing-Mentougou Debris-Flow Event

This study investigated the applicability of Fangshan X-band dual-polarization weather radar in the Mentougou debris-flow event occurred in the afternoon of June 18, 2017. Combined with the surrounding complex topography, the spatiotemporal characteristics of radar reflectivity in a $10 \times 10$ km area near the debris-flow explosion point were analyzed with the quality-controlled X-band dual-polarization radar data. The result shows that the occurrence and development of the heavy rainfall event can be effectively captured by the radar in the complex terrain areas where conventional automatic weather stations are scarce. The heavy rainfall lasts from 1230 LST to 1600 LST in the vicinity of the debris-flow, in which two consecutive heavy precipitation periods are observed. During the second period, the maximum reflectivity and the average reflectivity in the analysis area both reach maxima, and a distinct V-shaped gap is observed. Further analysis of quantitative precipitation estimation reveals that the interaction between the upstream water and the strong precipitation is an important cause of this debris-flow event. In conclusion, the X-band dual-polarization radar is capable of capturing the occurrence and development of locally heavy rainfall event in the mountainous area where conventional observations are scare.