华北暖季降水事件的小时尺度演变特征

Influenced by the different scale circulation, complex topography and underlying surface, the warm season rainfall over the northern China occupies a great part of annual rainfall. The heavy rainfall would induce the flood and geological hazard. Previous studies focusing on the climatological rainfall features over northern China often are at the daily or longer time scales and take the warm season rainfall as a whole. On the basis of analyzing the station rain gauge data, satellite products, reanalysis data and numerical simulations of climate model, the proposal mainly focus on the following four aspects: (1) analyze the regional and the hourly scale features of rainfall, in term of the rainfall events to enhance the comprehension of rainfall; (2) compare the mesoscale circulation before and after the rainfall event's beginning to improve the understanding of the evolvement of warm season rainfall; (3) classify the rainfall events based on the source areas and summarize the typical 3-D circulations which greatly influencing the heavy rainfall; (4) find the uncertainties of climate model in the simulation of hourly rainfall and circulation features to improve the capability of numerical model in precipitation forecasting and simulation.

华北地区暖季降水系统受下垫面强迫和不同尺度环流系统的综合影响，区域特征明显，极易引发旱涝和地质灾害。但目前对华北降水的气候研究多集中于日或更长的时间尺度，并将暖季降水作为整体进行分析，对降水事件的小时尺度演变特征的认识仍十分有限。本项目将依据台站观测资料、卫星遥感和再分析产品等，结合诊断分析和数值模拟，拟开展如下研究工作：（1）以降水事件为核心，分析华北地区降水的小时尺度特征及区域差异，分析地形和海陆分布对降水事件特征的影响，提高对华北降水性质和特征的科学认识；（2）研究降水发生前后对应的中尺度环流，增进对华北强降水形成机理和演变过程的理解；（3）按照降水系统生成源地将强降水事件分类，总结影响华北地区强降水的关键天气型及环流三维结构，为华北地区强降水的精细化预报提供参考；（4）以小时尺度降水及环流演变特征为标准，评估气候模式对华北降水的模拟能力，深入认识气候模式对降水模拟的不确定性。

本研究以华北暖季降水事件的小时尺度演变特征为研究对象，分析了复杂地形影响下华北地区小时时间尺度降水事件的基本特征以及区域差异；揭示了华北中心区不同类型强降水发生前的关键环流特征以及三维结构；研究了影响华北中心区山区降水是否下传的关键环流因子；建立了分析北京平原地区降水系统来向的分析方法；利用CAM5和WRF模式开展模拟试验，验证了高层暖异常对华北中心区强降水的关键作用。