新疆北部暖区暴雪的中尺度模拟及云微物理特征研究

Mesoscale Numerical Simulation and Cloud Microphysical Characteristics of the Warm Zone Blizzard in Northern Xinjiang

暖区暴雪罕见且易致灾,对其准确预报既是重点又是难点。本文采用WRF中尺度模式中Lin、Thompson、 WDM6和WSM6四种云微物理方案对2016年11月中旬一次典型新疆北部暖区暴雪过程进行数值模拟,评估模式对暖区暴雪过程的模拟能力,遴选最优参数化方案,分析暴雪过程中水凝物粒子垂直分布及演变特征,探讨导致暴雪过程的相关中尺度系统的发生发展规律。分析结果表明:(1)不同云微物理参数化模拟中,Lin方案效果最佳,较为成功地模拟出降雪量级、落区和趋势。(2)云中各种水凝物粒子活跃于对流层中下层,其中以霰和雪最多,自高层向低层分别分布着冰晶、雪、云水、霰粒子,阿尔泰山迎风坡附近为各水凝物粒子浓度大值中心,强降雪区四种云中水凝物粒子高值中心垂直对齐有利于各粒子间的转化。(3)上游高湿系统沿西路移动,低空偏南急流增强时水汽汇合强烈,阿尔泰山脉西麓迎风坡阻挡利于水汽辐合;低空偏南急流使暴雪区低层增温,不稳定条件增强,垂直次级环流发展,次级反环流的增强促进不稳定能量的释放,加剧垂直运动增长,为大暴雪的发展和维持提供较强的动力抬升条件,对暴雪起增幅作用。

The warm zone blizzard are both infrequent and highly destructive, making their accurate prediction a challenging and crucial focus.This study utilized four distinct cloud microphysics schemes (Lin, Thompson, WDM6, and WSM6) within the WRF mesoscale model to conduct a numerical simulation of a typical warm zone blizzard process in the northern Xinjiang in the middle of November 2016.The research objectives encompassed the evaluation of the model's capacity to simulate the warm zone blizzard, the selection of an optimal parameterization scheme, an analysis of the vertical distribution and evolution of hydrometeors during the snowstorm, and an exploration of the developmental patterns of related mesoscale systems contributing to the snowstorm.The analysis yielded the following key findings: (1) Among the diverse cloud microphysics parameterization schemes tested, the Lin scheme demonstrated the most favorable performance, effectively simulating snowfall magnitudes, spatial distributions, and trends.(2) In the cloud, all kinds of water condensate particles are active in the lower and middle troposphere, with graupel and snow being the most.Ice crystals, snow, cloud water and graupel particles are distributed from the upper layer to the lower layer.Near the windward slope of Altai Mountain is the center of the large concentration of each water condensate particle.The vertical alignment of the high value center of the four kinds of cloud water condensate particles in the strong snowfall area is conducive to the transformation of each particle.(3) High-humidity systems upstream moved westward, with the intensification of low-level southward jet streams resulting in pronounced moisture convergence.The western foothills of the Altai Mountains acted as a barrier, promoting moisture convergence by blocking the windward side;The low-level southerly jet also provides a continuous updraft and unstable condition for the generation of the blizzard.Strong snowfall is located in a wide updraft area between two groups of secondary circulations.The explosive growth of vertical movement is conducive to triggering the release of unstable energy, providing strong dynamic lifting conditions for the development and maintenance of the blizzard.