进入内陆的两个台风降水特征对比分析

Comparative analysis of the rainstorms caused by two typhoons in inland China

中文关键词:  台风  对比分析  水汽辐合  风垂直切变  雨滴谱

英文关键词:Typhoon  Comparative analysis  Moisture convergence  Vertical wind shear  Raindrop size distribution (DSD)

中文摘要:

      2012年8月台风海葵和2014年7月台风麦德姆登陆进入安徽省后，均造成了区域性暴雨或大暴雨天气。利用常规观测资料、NCEP/NCAR再分析资料和雨滴谱资料，对这两个直接影响安徽省的台风移动路径和暴雨形成机制进行了对比分析。结果表明：（1）海葵和麦德姆的移动路径、停留时间和强降水分布特征有明显不同。与海葵相比，麦德姆的移动速度快、降水持续时间短、累计降雨量和暴雨范围较小；但其短时强降水持续时间长、暴雨中心降水强度更大。（2）海葵和麦德姆降水过程中均有强的水汽输送和辐合，但水汽输送方向的差异使得海葵和麦德姆的强降水空间分布分别呈纬向型和经向型特征。同时水汽辐合持续时间决定了麦德姆的降水持续时间比海葵短，但其较深厚的强水汽辐合使得麦德姆的短时强降水持续时间长、暴雨中心降水强度大。（3）海葵是以稳定性降水为主的混合型降水，麦德姆则呈现出明显的对流性降水特征；两次台风降水过程中均是短时间的对流性降水对总降雨量贡献最大，且强降水区域均位于风垂直切变的顺风切左侧。（4）麦德姆降水过程比海葵具有更高的雨滴数浓度和更大的降水粒子直径。当雨强小于10 mm/h时，两次台风降水过程均以小雨滴为主且数浓度较大；雨强>10 mm/h时，雨滴粒径增大但数浓度明显降低。（5）两次台风降水过程的雷达反射率因子-雨强（Z-R）均有较好的指数关系且拟合曲线比较一致，但在不同降水类型即层云降水和对流性降水中，其Z-R关系的a、b值差异较明显。因此，针对不同降水类型，应采用分型Z-R关系来进行雷达降水定量估测。

英文摘要:

      Typhoon Haikui and Matmo made landfall in China and passed through Anhui Province in August 2012 and July 2014, respectively. Both of them caused regional heavy rainstorm in Anhui Province. By using daily observational data, the NCEP/NCAR reanalysis data and raindrop size distributions observed at Chuzhou, the tracks and the mechanisms of the rainstorms caused by the two typhoons are analyzed and compared. The results are as follows:(1) Typhoon Haikui and Matmo were distinctly different in their moving paths. The lasting time and heavy rainfall distributions of the rainstorms caused by the two typhoons were also quite different. Compared with Haikui, Matmo was characterized by faster moving speed, shorter rainfall duration, smaller cumulative rainfall and rainstorm range. In addition, the heavy rainfall duration associated with Matmo was longer and the precipitation intensity of the rainstorm center was greater. (2) Although strong water vapor transport and convergence occurred during the precipitation process associated with both Haikui and Matmo, their spatial and temporal distributions were different. Due to different water vapor transports, the heavy rainfall distribution of Haikui exhibited a zonal pattern,while that of Matmo showed a meridional pattern. Furthermore, the duration of moisture convergence can explain why the Matmo's rainfall duration was shorter than that of Haikui. However, the deep moisture convergence of Matmo made the heavy rainfall last longer and enhanced the rainfall intensity at the rainstorm center. (3) The precipitation of Haikui was a mixed type with the majority being stratiform precipitation, while the precipitation of Matmo was characterized by convective precipitation. During both of the two typhoon precipitation processes, short-period convective precipitation made large contribution to the total rainfall, and heavy rainfall mostly occurred on the left side of the area where environmental vertical wind shear occurred. (4) Matmo had higher raindrop concentration and larger raindrop size than Haikui. When the rainfall intensity is less than 10 mm/h, a large number of small raindrops contributed to the precipitation in both typhoons. On the contrary, when rainfall intensity is higher than 10 mm/h, the raindrop size increased while the number decreased. (5) The two typhoon precipitation processes showed a good exponential relationship between Z and R, which is consistent with their fitting curves. However, for different precipitation types of stratiform and convective precipitation, the values of a and b are obviously different in the Z-R relationship. Therefore, for different types of precipitation, different Z-R relationships should be used to estimate precipitation based on radar observations.