伊犁河谷短时强降水的时空分布及雷达回波特征分析

Analysis of the Spatio-Temporal Distribution and Radar Echo Characteristics of Short-Time Heavy Precipitation in the Yili River Valley

摘要: 本文利用伊犁河谷国家基本站和区域自动站2015年至2021年5至10月小时降水资料及伊宁新一代多普勒天气雷达资料，采用常规统计方法对伊犁河谷短时强降水天气时空分布及雷达回波参数值进行了研究分析。结果表明：(1) 伊犁河谷短时强降水空间分布呈山区多，平原少的特点，霍城县北部、伊宁县北部、尼勒克县、昭苏县、特克斯县及新源县东部等地的山区大部为显著的高发区并都处于山前的迎风坡处；(2) 近7a中，短时强降水年发生频次整体呈减少趋势，年平均为20次，2016年出现最多，2020年为最少年份；(3) 短时强降水有明显的月变化，自5月迅速增加，6月达到峰值，8月开始减少，6月至7月最为活跃；(4) 短时强降水的日变化呈单峰型结构，峰值出现时段在18~23时；河谷不同地区的日变化特征也不尽相同，西部、东部呈单峰型结构，而南部呈双峰型结构；(5) 当雷达回波参数值中最大回波强度 > 47 dBZ，垂直积分液态水含量 > 10.8 kg/m²，回波顶高 < 9.7 km，S35 > 37.2 km²时，伊犁河谷易发生短时强降水天气。

Abstract: This study analyzes the spatio-temporal distribution and radar echo parameters of short-time heavy precipitation in the Yili River Valley using hourly precipitation data from national basic stations and regional automatic stations in the valley, as well as Doppler weather radar data from Yining, Xinjiang, for the period from May to October between 2015 and 2021. The analysis employs conventional statistical methods. The results indicate that: (1) The spatial distribution of short-time heavy precipitation in the Yili River Valley is characterized by a higher frequency in mountainous areas and a lower frequency in plains. Most of the mountainous regions in the north of Huocheng County, the north of Yining County, Nilka County, Zhaosu County, Tekes County, and the east of Xinyuan County are significant high-incidence areas and are located on the windward slopes of the mountains. (2) Over the past seven years, the annual frequency of short-time heavy precipitation has shown an overall decreasing trend, with an average of 20 events per year. The highest frequency occurred in 2016, while the lowest was in 2020. (3) Short-time heavy precipitation exhibits a clear monthly variation, increasing rapidly from May, peaking in June, and decreasing from August, with the most active period being from June to July. (4) The diurnal variation of short-time heavy precipitation follows an unimodal pattern, with the peak occurring between 18:00 and 23:00. The diurnal variation characteristics also vary among different regions of the valley, with an unimodal pattern in the west and east, and a bimodal pattern in the south. (5) When the radar echo parameters exceed certain thresholds, specifically a maximum echo intensity greater than 47 dBZ, a vertical integrated liquid water content greater than 10.8 kg/m², an echo top height less than 9.7 km, and an S35 area greater than 37.2 km², short-time heavy precipitation is likely to occur in the Yili River Valley.