对流初生机理的研究进展

Research Advances in the Convective Initiation Mechanisms

对流初生(CI)是强对流天气开始活动的标志,CI机理研究是中尺度气象界研究的重点和难点,也是提高局地突发强对流天气演变的科学认知和短时临近预报水平的关键所在。文章综述了国内外地基CI机理和高架CI机理的研究成果。地基CI一般由边界层辐合线触发,温湿度扰动及不稳定性、微气旋、垂直切变和地形等因素都对CI的产生和时空位置有一定影响。大气不稳定性对局地温度尤其是湿度的变化很敏感,对CI的影响很大。环境垂直风切变与边界热动力场的相互配合,微气旋的垂直速度与涡度之间的反馈,地形导致的热动力效应,都会影响地基CI的产生。高架CI与低空急流、涌和重力波等有关。低空急流输送水汽,降低了环境的稳定度,其切变也可以产生上升气流,对夜间高架CI很重要。对流可以产生重力波和涌,两者通过抬升低层大气,减小稳定度,有利于高架CI的产生。高架辐合和持续的弱中尺度上升也有助于增加高架对流的潜势。综述内容对与CI有关的研究以及局地突发强对流的预报预警具有一定借鉴意义。

Convective initiation(CI)means the beginning of severe convective weather activities.The study of CI mechanisms is a critical and difficult problem of mesoscale meteorology,and is critical to improve the scientific knowledge of the evolution of local sudden severe convection and the nowcasting of severe convective weather.In this paper,the research results of surface-based CI mechanisms and elevated CI mechanisms at home and abroad are summarized.Surface-based CIs are usually triggered by boundary layer convergence lines.In addition,temperature and humidity disturbance,instability,misocyclone,vertical shear,topography and other factors also have a certain impact on the time and position of surface-based CIs.Atmospheric instability is sensitive to the change of local temperature,especially humidity,and has a great influence on CI.The interaction of ambient vertical wind shear and thermonamic field of boundary,the feedback between vertical velocity and vorticity of misocyclone,and the thermodynamic effects caused by topography all can influence the surface-based CIs.Most elevated CIs are related to the bores,gravity waves and low-level jets.The low-level jets transport water vapor upward and northward,reducing the stability of the environment,and the shear associated with the low-level jets can also produce updraft,which is important for nocturnal elevated CI.Convectively generated gravity waves and bores are conducive to the elevated CI,which can lift the lower atmosphere and reduce the stability.Elevated convergence and weak but persistent mesoscale lifting also help to increase the possibility of elevated CI.This article can be used for reference in the CI-releated research and the prediction and early warning of localized sudden severe convection.