中尺度天气系统适应性观测研究进展及其在大城市短临预报中的应用构想

Progress in targeted observation for meso-scale convective system and some thoughts on its applications to convection nowcasting in large cities

如何提高中尺度天气系统预报技巧是天气预报领域的重大科学问题之一。中尺度天气系统的发生和发展受到大气热动力条件、地形及污染条件等多重影响,且由于模式本身及初值的不确定性,中尺度天气系统所产生的对流天气预报仍有较大误差。通过在重点地区开展适应性观测试验降低模式初始场的不确定性是行之有效的方法之一,基于此有望更准确地揭示中尺度天气系统触发和形成机制、提高对流天气模式预报水平。首先,提出一种适应性观测试验的技术路线,即在已有的京津冀地区现代气象探测网基础上,采用集合变换卡尔曼滤波方法识别典型中尺度对流性天气的观测敏感区,结合无球探空移动观测平台,通过观测与预报互动方式,开展目标区的中尺度天气适应性观测试验,研究京津冀地区夏季对流天气触发机制,探索提高灾害性对流天气预报技巧的新方法。然后,针对大城市区域对流天气短临预报预警面临的低层大气垂直观测系统存在的“大网捞小鱼”问题,可通过构建由5个具有垂直观测能力的站点所组成的金字塔形对流层低层大气垂直观测系统,提出随云团大小和位置变化而变化的动态三角形组网观测技术,以获得不同空间尺度的大气动力廓线,进而增进对对流天气触发、发展和演变机理的认识。最后,探讨了适应性观测与大城市气象保障服务之间的内在联系,针对大城市大气垂直观测中尺度站网科学布局和以改进城市短临预报精度为目的的适应性观测等问题,给出具体建议,并展望以观测-预报互动为主要特征的中尺度适应性观测试验技术对大城市气象保障服务的科学价值和应用前景。

Improving the forecasting skills of the meso-scale convective system(MCS)is one of the key scientific problems in the field of nu⁃merical weather prediction.The occurrence and development of severe convective weather are affected by multiple factors such as atmospher⁃ic thermodynamic and kinetic conditions,topography,and air pollution conditions.Due largely to the uncertainty in models and the inevita⁃ble errors of initial values,large uncertainties still exist for the accurate prediction of severe weather produced by the MCS.Therefore,to ef⁃fectively improve the accuracy of severe convective weather forecasts in China,conducting targeted observation experiments in key areas of interest,which typically helps to reduce the uncertainty level of the model's initial meteorological field,may be one of the effective ways for⁃ward.It follows that the initiation and formation mechanisms of MCS can be revealed,and the forecast skills of severe convection will be im⁃proved.In this paper,we first propose the technology roadmap of targeted observation as follows.Based on the modern meteorological obser⁃vational network over the Jing-Jin-Ji area,the typical MCS forecast sensitive regions are identified by using the Ensemble Transform Kal⁃man filter,combined with the atmospheric sounding systems mounted on the mobile vehicle,where targeted observation experiments will be conducted.As such,convective initiation mechanisms are elucidated,and the novel methods expected to improve the forecast skill for MCS are explored.Secondly,in response to the challenge of"finding needles in a haystack"in the vertical observation of the lower atmosphere for short-term forecasting and warning of severe convective weather in large cities,the potential application value of a dynamic triangular obser⁃vation mesonet in the study of triggering and development mechanisms of severe convective weather was explored through the construction of a Pyramid-shaped LOwer Tropospheric Observational System(PLOTOS)that consists of five stations with simultaneous vertical observation capabilities.Finally,it is suggested that the initiation and formation mechanisms of severe convective weather be unraveled using PLOTOS,and the mesoscale targeted observation technology be developed,which is crucial to the improvement of weather observational networks in large cities and provide new ideas and methods for improving the forecast of severe convective weather processes.