基于高分辨率中尺度气象模式的实际雷暴过程的数值模拟试验

雷暴数值预报的实际应用离我们还有多远？本文对此进行了尝试, 即利用一个复杂的高分辨率中尺度气象模式驱动一个三维雷电模式, 在只采用常规气象观测资料的条件下, 对北京的一次实际雷暴过程进行模拟试验, 分析了雷暴云的宏观动力、 微物理过程及电结构的时空变化特征以及其可能的相互作用机制。结果表明: 利用高分辨中尺度模式预报出的三维气象场作为雷电模式的初始场, 完全可以不需添加虚假的扰动来触发雷暴云的发展, 高分辨中尺度模式的预报场本身所包含的水平非均匀、 垂直强非静力性及较强的对流不稳定信息足够促发雷暴云的剧烈发展; 用较为真实的三维气象场作为初始场模拟产生的电场分布特征与云微物理分布特征及环境气象要素的分布结构非常协调, 得到的雷暴云的电荷结构特征以及电结构随时间的演变特征更为复杂, 更真实的体现了实际雷暴云本身发展的复杂性, 同时, 模式能够模拟出合理的云闪及正负云地闪, 且模拟的闪电频数随时间发展演变趋势基本与观测实况基本吻合, 从而表现了对雷电天气潜在的预报能力。本次模拟的北京雷暴云在发展过程中, 水物质霰的最大质量比、 最大正电场强度及闪电频数随模拟时间的演变发展趋势非常相似。

Numerical simulation experiments of a thunderstorm process based on a high|resolution mesoscale model

How far will the thunderstorm numerical forecast be used routinely? To answer this question, a three-dimensional thunderstorm electrification and lightning model coupled with a high-resolution mesoscale model is used to simulate a thunderstorm process occurring in Beijing. In this paper, the characteristics of spatial-temporal evolutions of kinematics, microphysics and electrification, as well as the probable interaction between them are analyzed. Results show that a thunderstorm can be triggered without adding an artificial perturbation cell, in which the initial conditions are provided by the high-resolution mesoscale model. The meteorological information from the mesoscale model includes horizontal nonhomogenous and vertical nonhydrostatic information and intense convective instability can accelerate the thunderstorm development violently. The simulated electrical field, cloud microphysics field and background fields are reasonable, and the electrical structure and its spatial-temporal evolvement are more complex, which is closer to the real character of thunderstorm. At the same time, the coupling mesoscale weather model with the electrical and lightning model can simulate a profuse amount of reasonable cloud flashes and negative (positive) polarity cloud-to-ground (CG) flashes, and also the temporal evolution characteristics of cloud ground flash frequency are basically near to the observations. This indicates that the model has potential in the research and forecast of thunder weather. The case simulation reveals that the temporal evolution trends of flash frequency, the maximum graupel mixing ratio and the maximum positive electric field intensity are very similar.