The Characteristics of Raindrop Size Distribution in Two Rainstorms with Extreme Rainfall Rates in Summer in Shandong Province
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摘要: 利用Thies激光雨滴谱仪观测的两次极端雨强暴雨的雨滴谱资料,结合CINRADA/SA多普勒雷达观测资料,分析了极端雨强对流降水雨滴谱和积分参数特征、以及地面雨滴谱的形成机制,主要结论为:(1)两次过程都是受副热带高压外围西南气流与西风槽共同影响,具有高温高湿的特点,有利于强降水的产生。(2)强对流降水(雨强R>20 mm h−1)雨滴谱参数lgNw、D0与雨强R关系显示,2015年8月3日参数D0随着R增大很快增大,线性拟合线的斜率较大,lgNw随着R增大逐渐减小,线性拟合线的斜率为负值;2017年7月26日D0和lgNw与R都是正相关,但D0和lgNw随着R增大较缓慢地增大,线性拟合线的斜率较小。强对流降水雨滴浓度NT与雨强R之间的关系可以用幂函数拟合,8月3日有较大系数和较小指数,7月26日有较小系数和较大指数。(3)不同雨强的对流降水平均雨滴谱分布显示,8月3日随着雨强增大(R>50 mm h−1),直径1~3 mm中小粒子数密度相差不大,直径3~6 mm大雨滴的粒子数密度明显增大,对流降水Z–R关系有较大指数(1.61);7月26日随着雨强增大各直径档的粒子数密度基本同时增大,对流降水Z–R关系有较小指数(1.25)。综合各种参数与雨强关系和平均雨滴谱分布特征判断,8月3日强对流降水雨滴谱属于典型的尺寸控制雨滴谱特征,而7月26日对流降水属于浓度—直径混合控制的雨滴谱特征。(4)雨滴谱归一化Gamma函数参数Nw–D0分布显示,两次对流降水都具有典型大陆性对流降水雨滴谱特征,对流降水主要属于冰相对流降水雨滴谱,但8月3日过程有较多雨滴谱属于冰相—暖雨混合对流降水雨滴谱特征。Abstract: Abstrcat The raindrop size distributions and integral parameters of convective precipitation and formation mechanism of ground Raindrop size distribution in two extreme precipitations were analyzed using data from the Thies disdrometer and the CINRADA/SA Doppler radar. The results showed that: (1) The two precipitation processes were both affected by the southwest airflow outside the subtropical high and the westerly trough with the characteristics of high temperature and high humidity, which were conducive to the production of heavy rain. (2) The relationships between parameters lgNw, D0 and rain intensity R of severe convective precipitation episodes (rain intensity R>20 mmh−1) revealed there was a large coefficient and a small index on 3 August 2015, whereas it was just the opposite on 26 July 2017. On 3 August, D0 rapidly increased as R increased for the median volume diameter of the raindrop, and the slope of the fitting line was large, while lgNw gradually decreased as R increased. Furthermore, the slope of the linear fitting line was negative. D0 and lgNw were both positively correlated with R on 26 July 2017; however, D0 increased slowly as R increased, and the slope of the fitting line was small. In addition, the slope of the linear fitting line was smaller. For the raindrop concentration (NT), the exponential function can be used to fit the NT as R increases. On 3 August, there was a large coefficient and a small index, whereas on 26 July, it was just the opposite. (3) The average raindrop size distribution of convective precipitation with different rainfall intensities show that, On 3 August, with the increase of rain intensity (R>50 mm h−1), the concentration of small particles in diameter 1–3 mm varied slightly, while the concentration of large raindrops in diameter 3–6 mm increased significantly, and the Z–R relationship of convective precipitation had a large index (1.61). On 26 July, with the increase of rain intensity, the concentration of particles in each diameter range basically increased at the same time, and the Z–R relationship of convective precipitation had a small index (1.25). In conclusion, the precipitation on 3 August had typical size-controlled raindrop size distribution characteristics, whereas the convective precipitation on 26 July had concentration–diameter mixed control of raindrop size distribution characteristics based on the relationship between integral parameters and rain intensity and the average raindrop size distribution. (4) The normalized Gamma NW–D0 distributions showed that the convective precipitation in the two cases had the characteristics of the typical raindrop size distribution of continental convective precipitation. Many raindrop size distributions in the processes of 3 August showed the characteristics of ice phase and warm mixed convective precipitation, but most of the convective precipitation in the two processes had the characteristics of ice-based raindrop size distribution.
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图 1 2015年8月3日(a)17:41(北京时,下同)、(b)19:43、(c)20:30济南(36°48'10"N,116°46'51"E)新一代多普勒雷达组合反射率(单位:dBZ),(d)济南雨滴谱仪站点(36°41'N,117°32'E)雷达反射率因子(单位:dBZ)高度—时间剖面
Figure 1. Composite reflectivity (units: dBZ) of new generation Doppler radar at Jinan (36°48'10"N, 116°46'51"E) at (a) 1741 BJT (Beijing time), (b) 1943 BJT, (c) 2030 BJT, and (d) height–time profile of radar reflectivity (units: dBZ) for disdrometer at Jinan station (36°41'N, 117°32'E) on 3 August 2015
图 2 2017年7月26日(a)19:28、(b)20:15、(c)21:50临沂(35°15'00"N, 118°25'12"E)新一代多普勒雷达组合反射率(单位:dBZ),(d)蒙阴雨滴谱仪站点(35°42'N,117°56'E)雷达反射率因子(单位:dBZ)高度—时间剖面
Figure 2. Composite reflectivity (units: dBZ) of new generation Doppler radar at Linyi (35°15'00"N, 118°25'12"E) at (a) 1928 BJT,(b) 2015 BJT,(c) 2150 BJT, (d) height–time profile of radar reflectivity (units: dBZ) for disdrometer at Mengyin station (35°42'N, 117°56'E) on 26 July 2017
图 3 2015年08月03日济南(a)雨滴谱N(D)(单位:m−3 mm−1),(b)雨滴数浓度NT(黑色线,单位:m−3)、反射率因子Z(蓝色线,单位:dBZ)和雨强R(红色线,单位:mm h−1),(c)归一化Gamma谱参数lgNw(绿色线)和D0(黑色线,单位:mm)的时间序列
Figure 3. Temporal evolutions of (a) raindrop size distribution N(D) (units: m−3 mm−1), (b) raindrop number concentration NT (black line, units: m−3), reflectivity factor Z (blue line, units: dBZ), and rain rate R (red line, units: mm h−1), (c) normalized Gamma spectral parameters lgNw (green line) and D0 (black line, units: mm) at Jinan on 3 August 2015
图 4 2017年7月26日蒙阴(a)雨滴谱N(D)(单位:m−3 mm−1),(b)雨滴数浓度NT(黑色线,单位:m−3)、反射率因子Z(蓝色线,单位:dBZ)和雨强R(红色线,单位:mm h−1),(c)归一化Gamma谱参数lgNw(绿色线)和D0(黑色线,单位:mm)的时间序列
Figure 4. Temporal evolutions of (a) raindrop size distribution N(D) (units: m−3 mm−1), (b) raindrop number concentration NT (black line, units: m−3), reflectivity factor Z (blue line, units: dBZ), and rain rate R (red line, units: mm h−1), (c) normalized Gamma spectral parameters lgNw (green line) and D0 (black line, units: mm) at Mengyin on 26 July 2017
图 6 (a、b)2015年8月3日济南、(c、d)2017年7月26日蒙阴雨滴谱仪观测的参数(a、c)D0、(b、d)lgNw与雨强R的散点图和拟合线
Figure 6. Scatter plots and fitting results of (a, c) the median volume diameter D0, (b, d) the intercept parameter lgNw versus rain rate R retrieved from raindrop size distributions (a, b) at Jinan on 3 August 2015, (c, d) at Mengyin on 26 July 2017
图 7 (a)2015年8月3日济南、(b)2017年7月26日蒙阴雨滴谱计算的雷达反射率因子Z与雨强R的散点图和拟合线。实线是强对流降水(R>20.0 mm h−1)拟合方程,点划线是个例一层状降水S2和个例二层状降水拟合方程,虚线是新一代多普勒雷达对流降水Z–R关系
Figure 7. Scatter plots and fitting results of radar reflectivity factor Z versus rain rate R retrieved from raindrop size distributions (a) at Jinan on 3 August 2015 and (b) at Mengyin on 26 July 2017. The solid line represents the fitting equation of strong convective precipitation, the dotted line represents the fitting equation of case 1 stratiform precipitation S2 and case 2 stratiform precipitation, the dotted line represents the new generation Doppler radar convective precipitation Z–R relationship
图 9 (a)2015年8月3日济南、(b)2017年7月26日蒙阴的lgNw–D0散点图和对流—层状降水分离线(黑实线)。绿色矩形框自上而下分别是海洋性和大陆性对流分布(Bringi et al, 2003),虚线是层状降水平均分布,点划线是对流与层状云降水之间的分离线(Bringi et al, 2009)
Figure 9. Scatter plots of lgNw versus D0 and the convection–stratiform separation (black solid line) line (a) at Jinan on 3 August 2015 and (b) at Mengyin on 26 July 2017. The two green rectangles correspond to the maritime and continental convective clusters reported by Bringi et al. (2003), the dashed line represents the average of stratiform, the dotted-dashed line represents the stratiform–convective separation line proposed by Bringi et al. (2009)
表 1 2015年8月3日济南8类雨滴谱的雨强、样本数、参数lgNw和D0以及平均雨强
Table 1. Rain intensity R, number of samples, parameters lgNw and D0, mean rain intensity retrieved from 8 categories of raindrop size distributions at Jinan on 3 August 2015
雨滴谱
类型雨强R/
mm h−1样本数/
minlgNw/m−3
mm−1D0/
mm平均雨强/
mm h−1T 4<R≤9.9 9 3.49 1.69 7.2 S1 2<R≤10 24 3.29 1.88 7.3 S2 0.5<R≤15 120 2.33 2.86 5.5 1 10<R≤50 31 3.44 2.34 26.3 2 50<R≤100 24 3.52 2.98 75.6 3 100<R≤200 18 3.17 4.05 135.9 4 200<R≤300 2 3.30 4.28 244.3 5 R>300 2 3.23 4.90 384.8 表 2 2017年7月26日蒙阴6类雨滴谱的雨强、样本数、参数lgNw和D0以及平均雨强
Table 2. Rain intensity R, number of samples, parameters lgNw and D0, mean rain intensity retrieved from 6 categories of raindrop size distributions at Mengyin on 26 July 2017
雨滴谱
类型R/
mm h−1样本数/
minlgNw/m−3
mm−1D0/
mm平均雨强/
mm h−1S 0.5<R≤9.0 70 2.03 2.67 2.7 1 10<R≤50 21 3.19 2.69 30.6 2 50<R≤100 16 3.33 3.06 73.2 3 100<R≤200 15 3.68 3.00 143.9 4 200<R≤300 3 3.82 3.32 271.9 5 R>300 1 3.78 3.67 390.6 -
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