CHARACTERISTICS OF THE RAINDROP SIZE DISTRIBUTION IN TWO SQUALL LINES MEASURED BY TWO-DIMENSIONAL VIDEO DISDROMETER AT GUANGDONG
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摘要: 基于中国气象局龙门云物理野外科学试验基地2DVD(Two-Dimensional Video Disdrometer)雨滴谱观测资料, 分析广东地区2017年5月4日(槽前型飑线)和2017年8月22日(东风型飑线)两次不同飑线系统不同降水类型的雨滴谱特征。根据雨强和雷达反射率随时间变化将降水分成对流降水和层云降水, 同时以20 mm/h为阈值将对流降水划分为对流前沿、对流中心和对流后沿。结果表明, 两次飑线系统在不同降水时期的微物理特征参数变化有所差异。槽前型飑线过程中, 对流降水的粒子分布较为分散, 中等粒径的粒子比重较高, 且对流区前半部分粒子尺寸大于“大陆性”对流特征, 后半部分粒子尺寸小于“海洋性”对流特征; 层云降水的粒子分布较为集中, 小粒径粒子居多。而东风型飑线整个降水时期基本上是由高浓度中小粒径粒子组成, 降水粒子粒径分布较为集中, 对流降水粒子介于“海洋性”和“大陆性”对流区之间。Abstract: Temporal evolution and spatial variations of the raindrop size distribution(DSDs)in two types of squall lines (in front of trough and within east wind) are analyzed based on a two-dimensional video disdrometer (2DVD) from Longmen Field Experiment Base on Cloud Physics, China Meteorological Administration. According to the temporal variation of precipitation rate and radar reflectivity, the precipitations are categorized into convective and stratiform rain. Moreover, the convective rain is classified into leading edge, convective center and trailing edge based on the threshold rain rate of 20 mm·h-1. Results show that in squall line in front of trough, the DSDs are characterized by a higher concentration of small drops in stratiform rain, a larger sized drops for leading edge and convective center as compared with "continental-like" clusters, also a smaller sized drops for trailing edge as compared with "maritime-like" clusters. In squall line within east wind, the DSDs are characterized by narrower and smoother spectra, a higher concentration of midsize and small drops, and the raindrops of convective rain are within the range of "maritime" and "continental" clusters.
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Key words:
- squall line /
- raindrop size distribution /
- precipitation classification
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表 1 不同降水类型降水贡献和Nt、W、R、Dm和lgNw的平均值
时间 降水类型 样本个数
个/minR/(mm/h) 降水贡献/% Nt/m-3 W/(g/m3) Dm/mm lgNw/(mm-1·m-3) 20170504 对流降水 10 42.20 75.3 20 165 2.01 2.36 3.81 层云降水 33 4.20 24.7 2 076 0.27 1.16 4.03 20170822 层云降水(前) 52 3.05 20.0 560 0.16 1.54 3.30 对流降水 14 34.32 60.7 12 716 1.58 2.03 3.81 层云降水(后) 55 2.77 19.3 559 0.15 1.39 3.52 -
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