鄂北短时强降水特征及双偏振雷达预警指标

Short-time heavy rainfall characteristics and dual polarization radar warning indicators in northern Hubei

摘要:

利用湖北省随州市70个自动气象站逐小时降水观测资料以及双偏振雷达观测资料，对2019－2023年短时强降水的分布特征和不同等级雨强的双偏振雷达参数特征进行统计分析，结果表明：(1)短时强降水集中在6－8月，6－7月频次最多；日变化特征呈三峰型分布，最多出现在早晨05—08时，其次是上半夜22—01时，第三是午后到傍晚13—18时。从区域分布来看，随州南部较中北部更易出现短时强降水，随县南部是短时强降水最高发易发区。(2)与雨强相关性高的雷达参数有组合反射率CR和垂直积分液体含水量VIL和2.5 km以下低层的水平反射率因子ZH、差分传播相移率KDP。随着雨强的增大，ZH、KDP、CR以及VIL总体趋势均是增大的，而差分反射率因子ZDR、相关系数（Correlation Coefficient, CC)、回波顶高ET和最大回波高度DBZM HT变化趋势与雨强的关系并不明显。(3)雨强等级越大，ET和ZDR越大，表示其回波顶越高，对流发展越旺盛，粒子直径越大。(4)20~40 mm·h-1和≥40 mm·h-1雨强对应的低层ZH、ZDR、KDP、CC以及CR、ET、DBZM HT、VIL的短临预警指标值分别是37 dBZ和41.2 dBZ、0.77 dB和0.92 dB、0.34 deg·km-1和0.65 deg·km-1、0.95和0.96、39.2 dBZ和43.3 dBZ、6.5 km和7.6 km、1.8 km和1.8 km、2.9 kg·m-2和4.5 kg·m-2。

Abstract:

Based on the hourly precipitation observation data of 70 stations and the observation data of dual polarization radar in Suizhou City, Hubei Province, the distribution characteristics of short-time heavy rainfall and the characteristics of dual polarization radar parameters of different levels of rainfall intensity from 2019 to 2023 were statistically analyzed. The results show that: (1) The short-time heavy rainfall is concentrated in June to August, with the most frequent in June to July. The daily variation characteristics show a three peak distribution, with the highest occurrence occurring from 05:00 to 08:00, followed by 22:00 to 01:00, and the third occurring from 13:00 to 18:00. From the perspective of regional distribution, the south of Suizhou is more prone to short-time heavy rainfall than the north, and the south of Suixian is the most prone area. (2) The radar parameters with high correlation with rain intensity are combined reflectivity(CR), vertical integrated liquid water content (VIL), and differential reflectivity(ZDR), specific differential phase (KDP) below 2.5 km. With the increase of rainfall intensity, the general trends of horizontal reflectivity(ZH), KDP, CR and VIL increase slightly, while the correlation between rainfall intensity and ZDR, correlation coefficient(CC), echo top height(ET) and maximum echo height(DBZM HT) is not obvious. (3) The higher the rain intensity, the greater ET and ZDR, indicating that the higher the echo top, the stronger the convection development, the larger the particle diameter. (4) The early warning index values of ZH, ZDR, KDP, CC at low levels and CR, ET, DBZM HT and VIL corresponding to rainfall intensity of 20~40 mm·h-1 and ≥40 mm·h-1 are respectively 37 dBZ and 41.2 dBZ、0.77 dB and 0.92 dB、0.34 deg·km-1 and 0.65 deg·km-1、0.95 and 0.96、39.2 dBZ and 43.3 dBZ、6.5 km and 7.6 km、1.8 km and 1.8 km、2.9 kg·m-2 and 4.5 kg·m-2.