中文摘要：

基于WRF模式多普勒雷达同化预报、1°×1°的NCEP再分析资料、云图TBB和本地加密观测资料，对2014年8月12日关中地区突发性暴雨过程（“0812”暴雨）进行诊断分析。结果表明：同化C波段雷达资料能有效提升WRF对此次突发性暴雨的预报能力。受中高层北部冷空气侵入和低层冷式切变南压的影响，在“0812”暴雨期间，关中的北部和东部的地面切变辐合线附近先后出现了南北向和东西向的中 尺度重力波，波动持续约4 h、波长约60 km。当北部波动向南传播发展与东部波动合并之后，重力波快速消散，强降水结束。暴雨发生前，波动区的垂直上升速度、雨水含量中心强度和发展高度均迅速达到最大，陕北地区对流层中上部的正湿位涡显著向南下滑至关中上空，出现了有利于中尺度波动发展的湿位涡波列结构，暴雨中心近地层的正湿位涡和垂直梯度异常增大。200 hPa高空急流区南侧、关中西部垂直风切变显著增大及其东移南压为中尺度波动快速发展、传播提供了能量。500 hPa内蒙古中部天气尺度横槽发展东移、引导中低层偏北路冷空气南压，是突发性暴雨直接影响系统。850 hPa的比湿突增为暴雨提供了热力、水汽条件。近地层显著东南风、不稳定扰动增大和地面切变线是暴雨的有利动力、触发条件；在地面切变线西端附近，3 h变压场出现显著中尺度波动特征。“0812”暴雨与典型盛夏暴雨差异明显：西太平洋副热带高压远离大陆、东南沿海无台风活动，关中低层出现西北路水汽输送，强降雨区周边700 hPa以上深厚位势稳定层结、近地层不稳定层结垂直叠置有利于重力波动发展传播，中尺度对流云团高度低，雷达强降水回波主要位于低层西北风和东北风之间的冷式切变区。

英文摘要：

NCEP 1°×1° reanalysis, TBB, local density observation data and WRF forecast assimilated by Radar are used to analyse mesoseale characteristics of the abrupt rainstorm occurred at Guanzhong on 12 August 2014（ ＂0812＂ rainstorm）. Results show that： Prediction performance of ＂0812＂ rainstorm by WRF assimilated with C band Radar is improved effectively. On the influence of cold air intrusion from north at middle and upper levels and southward cold shear at Sow level, meso-fl gravity waves including the north to southward part around the northern Guanzhong and the east to westward part around the eastern Guanzhong are produced successively. The latter wave near the surface wind shear line. Wavelength of Mesoscale gravity fluctuation are about 60km and duration about 4 hours. Gravity wave dissipated and rainstorm stop after connection between the north part propagating southward and the east part of waves. Intensity and develop height of upward vertical velocity and rainwater content reach maximum near fluctuation region just before the rainstorm. At precipitation beginning, positive Moist Potential Vorticity （MPV） in upper troposphere over the northern part of Shaanxi Province is significantly southward and downward to Guanzhong and MPV with its vertical gradient are anomaly increase over rainstorm center. Mesoscale fluctuations of MPV are conducive to the mesoscale wave development. Vertical wind shear significantly increase and move eastward and southward around areas of south side of Jet flow near western Guanzhong at 200 hPa provide energy for mesoscale fluctuation development and propagation. Synoptic scale horizontal trough moving eastward at 500 hPa near central Mongolia and leading northerly cold air move southward at Sow levels, which is the direct affecting system on abrupt rainstorm. Humidity increased quickly at 850 hPa provides thermal and moisture condition for rainstorm. Significantly southeast wind near ground and unstable disturbance surge and ground shear line are favorably trigge