Coverage Capacity of Hail Detection for Yunnan Doppler Weather Radar Network

Weather radar is a powerful tool for hail detecting, but the detection ability of Doppler weather radar network is influenced not only by weather radar volume coverage pattern (VCP) strategy, but also radar beam blockage due to the complex terrain in mountainous areas. Hail storm cells emerge on the low-level area far from the radar and near the cone of silence is often underestimated. In addition, meteorological scatter objects are distorted at less terrain blockage areas or even can't be detected completely at severe blockage area. Radar beam blockage by various terrain shape in mountainous region is very common, resulting in some of storm cells difficult to identify by weather radar network. Therefore, an assessment method of hail observation ability for Doppler weather radar network is proposed, based on the average height of 0℃, -20℃ level and the height of the core of storm cells. The multiple layer grid data of three-dimensional coverage for Yunnan C-band Doppler weather radar network is built up by combining the radar beam hybrid scanning method with the high-resolution Shuttle Radar Topography Mission (STRM) terrain data. According to characteristics of the hail cell stretching level, the coverage scope above 0℃ level of weather radar network is considered as an assessment method to evaluate hail detecting capabilities of weather radar network. Based on C band Doppler weather radar network in Yunnan Province, 607 hail ground report samples are collected during 2014-2016 to analyze capabilities and limitations of hail detection in the low-latitude plateau, and the detection area classification is summed up. Results show that it is reasonable for judging effects of the hailstorm detection with the height of 0℃ level and several height differences. The suitable detecting area account for roughly 75% throughout the province. Areas located in the northeast part of Zhaotong prefecture and the northeast part of Lincang prefecture are evaluated as hail detecting disadvantaged zone because of severe terrain blockage. Theoretically, with weather radars, based on the hailstorm probability during 2014-2016, over 90% hailstorm in Yunnan can be monitored and recognized effectively. About 3% hailstorm cell can be recognized when higher than 8 km, and about 6% hailstorm falls around radars that only cover below 8 km, and these may cause underestimation. 8.5% area of Yunnan is still beyond coverage, and 9 radars will be put into operational observation network. The proposed method can be used for assessing the ability of hailstorm detecting with the Doppler weather radar network quantitatively.