中尺度对流系统的闪电观测资料同化方法及评估研究

Mesoscale convective systems (MCSs) are major precipitation processes, and often lead to flooding and disastrous consequences in northern China as well. The initial fileds of numerical weather prediction models are great important for the precipitation forecast of MCS processes. Lightning can provide accurate information regarding to the location of severe convection, and has a close relationship with microphysical and dynamic processes inside the cloud. This project will use the synchronized comprehensive data of MCS obtained by the well-installed lightning detection network and dualliner polarization and Dopper radar sysyem in Beijing area. The relashinship between lightning and the characterized parameters related to the microphysical and dynamic processes inside the cloud will be studied as to construct the nudging assimilation adjustment functions for modifing the initial fields of the numerical weather prediction model. The lightning assimilation techniques, based on the nudging assimilatin functions with observed lightning data, will be applied into the numerical weather prediction model, and to verify its capability of improving the forecasting of MCS precipitation. The quantitative assessment method will be developed to evaluate effects of the proposed lightning data assimilation technique, and the well-developed radar data assimilation technique will be adopted for comparision as well. A kind of synthesized assimilation technique combining both lightning and radar data will be attempted as to providing a kind of methodology for the short term forecasting of MCS. The lightning assimilation technique is one of the frontier scientic questions related to atmospheric electricity, and it is significant not only for the enhancement of the simulation capability of the numerical weather prediction model, but also for the improvement of the short term forecasting of the disastrous MCS with high precipitation intensity.

中尺度对流系统是我国中纬度地区造成暴雨灾害的主要降水系统，也是一种重要的高影响天气事件，中尺度模式初始场对降水预报的准确率有重要影响，而闪电活动可提供较准确的强对流发展信息和位置，与云动力过程和微物理过程也有密切关系。本项目将综合利用闪电探测和定位网、多普勒雷达等所获取的中尺度对流系统同步观测资料，研究建立总闪电频数（云闪和地闪）与云动力和微物理过程特征参量之间的关系，构建闪电资料对中尺度模式初始场的同化调整函数；结合数值模拟，探讨闪电资料同化在云分辨尺度上对中尺度对流系统降水预报的改进能力，并发展其定量评估方法。与国际通用的雷达资料同化方法进行对比，建立基于闪电和雷达两种资料的综合同化方法，为改进强对流天气的短时预报提供新方法。闪电资料同化方法研究不仅是当前国际上重要的前沿科学问题，而且对增强中尺度数值模式的模拟能力、提高灾害性天气的短时预报水平也有十分重要的应用价值。

闪电可以准确指示强对流系统的发生发展，借助高精度总闪（云闪+地闪）定位资料，研究中尺度对流系统MCS的闪电活动规律，发展有效的闪电资料同化方案，有利于提升对强对流天气的预报水平。本项目基于北京闪电探测网BLNET的总闪定位资料和天气雷达资料，开展了对流系统的闪电特征及其与动力、微物理参量的关系分析，发展了两种闪电资料同化方法，并在数值预报模式中进行了同化应用，显著改进了强对流预报。.主要进展包括：1）开展了四个夏季的闪电综合观测实验，获得了大量雷暴个例的闪电定位资料；同时改进了BLNET定位算法，评估了BLNET探测性能，发现其总闪探测效率为93.2%。2）基于总闪资料和多普勒天气雷达资料，研究了北京地区MCS中闪电与云内动力和微物理过程之间的关系，并在此基础上研究了负地闪回击所中和的电荷信息；利用全球闪电定位资料，研究了西北太平洋地区热带气旋闪电活动的气候学特征及其与气旋强度变化的关系。 3）发展了两种闪电资料同化方案，一是综合调整水物质含量的总闪资料同化方案，并基于Nudging方法在WRF模式中进行同化试验，改进了降水预报；二是调整垂直上升气流速度的雷电四维变分同化方案，并基于VDRAS模式进行了同化实验，结果表明闪电与雷达资料的协同同化方案较仅同化雷达资料在定量降水预报效果方面得到明显的改进，并具有抑制虚假对流的效果。研究结果为强对流天气的短时预报提供了新手段, 对强对流模拟和强降水预报有重要的科学意义和实际应用价值。.目前为止，项目共发表论文15篇，其中SCI收录论文6篇，国内核心期刊收录论文6篇，国际会议论文集收集论文3篇。项目共培养博士生7名，硕士生3名。项目研究工作在EGU，AGU以及ICAE等国际学术会议上口头报告6人次，包括国际会议特邀报告1人次；另有国内学术会议邀请报告4人次。