三维强风暴动力-电耦合数值模拟研究Ⅰ:模式及其电过程参数化方案

为了研究风暴中的动力、微物理和电过程三者间的相互作用 ,在已有的工作基础上 ,建立了一个三维强风暴动力 电耦合数值模式。模式中将云中水物质分为水汽、云水、雨水、冰晶、雪、霰和雹 7类 ,各种粒子采用双变参数谱。考虑了详细的起电过程 ,它们包括扩散、电导、感应和非感应以及次生冰晶起电机制。此外 ,在模式中加入了云内放电参数化过程和云顶处屏蔽电荷层形成的参数化方案用以研究整个雷暴生命史内的电活动特征。最后利用CCOPE(CooperativeConvectivePrecipitationExperiment)计划中 1981年 7月 19日的风暴资料对模式的性能进行了验证 ,模拟结果显示此模式可以较好地描述风暴中动力、微物理和电结构的发展演变过程。

NUMERICAL STUDY OF THUNDERSTORM ELECTRIFICA-TION WITH A THREE-DIMENSIONAL DYNAMICS AND ELECTRIFICATION COUPLED MODEL Ⅰ:MODEL DESCRIPTION AND PARAMETERIZATION OF ELECTRICAL PROCESSES

A new three-dimensional dynamics and electrification coupled model has been developed for investigating the characteristics of microphysics, dynamics and electrification inside thunderstorms. This model is basically modified from a three-dimensional, time-dependent, and dual-parameter cloud model originally established in IAP (Institute of Atmospheric Physics) and a two-dimensional axisymmetric cloud dynamics and electrification coupled model. Primary modifications to the model include not only the coupling of electrification with dynamical and microphysical processes, but also the lightning discharge process and screening layer effect at the cloud top as well. Apart from including a full treatment of small ions with attachment to seven classes of hydrometeors(water vapor, cloud drops, rain, ice, snow, graupel and hail), the model considers ten microphysical processes which include condensation, deposition, evaporation, autoconversion of cloud-rain, collection, freezing melting, nucleation,, and multiplication of ice crystals, and five electrification processes which include ionic diffusion, electric attraction, inductive charging, non-inductive charging and secondary ice crystal charging. The larger precipitation particles are also forced by the vertical component of electrical force in electrical intensive thunderstorms. For the horizontal and vertical advection terms, fourth-order and second-order finite differences are used, and super relaxation method is used to determine electric potential. A case simulation of July 19 in 1981 CCOPE is performed aiming to validate the potential capability of the model. Comparison between model results and observations reveals that the model has the capacity to reproduce many of the observed characteristics of thunderstorms in dynamical, microphysical, and electrical aspects.