摘要
根据米散射雷达截面公式,分别利用模拟M-P谱分布和模拟强降水对流谱分布以及实测强降水雨滴谱资料,计算粒子直径6次方之和(Zd)与3.2 cm、5.5 cm和10 cm三种波长雷达的等效反射率因子值(Ze)及二者之间的差值,进而分析其对雷达定量测量降水的影响。结果表明:随着降水强度增大,单位体积内雨滴个数(N)、大雨滴含量和Zd值均增加,对3.2 cm波长雷达,Ze>Zd且Ze-Zd增大,差值超过2 dB;对5.5 cm波长雷达,Ze由小于Zd值逐渐转变为大于Zd值,差值在±1 dB左右;对10cm波长雷达,Ze<Zd且|Ze-Zd|增大,差值达-1 dB;在同一滴谱分布下,波长越短,大雨滴对雷达反射率因子测量值影响越大,对雷达定量测量降水影响越严重。
According to the Mie backscattering cross-section formula, three types of drop size distributions （DSD）, i.e., the M-P distribution, the simulated convective precipitation DSD and the heavy rain observations by disdrometer, are used to calculate the sum of the diameter＆#39;s sixth power of all raindrops （Zd）, the equivalent reflectivity factors （Ze） of 3.2 cm, 5.5 cm and 10 cm radars, and their corresponding differences to analyze effects of the differences on quantitative precipitation estimation （QPE）. The results show that as precipitation becomes stronger, the total number density of all raindrops （N）, the number density of large raindrops and Zd all increase. As the number of large raindrops increas-es, for 3.2 cm wavelength radar, Ze is greater than Zd, and their difference increases with rainfall intensity. The maximum difference might ex-ceed 2 dB. For 5.5 cm wavelength radar, Ze changes from less than Zd to greater than Zd as rainfall intensity increases;the difference varies from-1dB to 1 dB. For 10 cm wavelength radar, Ze is always less than Zd and their difference might reach to-1 dB. Hence, when large rain-drops existing, the shorter the wavelength is, the less accurate the radar reflectivity factor is under the same raindrop size distribution, which directly results in inaccurate QPE.
出处
《暴雨灾害》
2014年第2期106-111,共6页
Torrential Rain and Disasters
基金
2011年度公益性行业(气象)科研专项(GYHY201106406)
关键词
大雨滴
雷达
定量测量降水
等效反射率因子
large raindrops
radar
quantitative precipitation estimation
equivalent reflectivity factor
