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一次伴有雷暴大风的飑线天气过程分析及数值模拟研究

     

摘要

利用NCEP/NCAR(1°×1°)的逐6h再分析资料、WRF中尺度预报模式,对2014年7月30-31日发生在江淮地区的一次强飑线天气过程进天气学分析和数值模拟研究.研究结果表明,此次飑线过程是在高空槽后有强冷空气输送、中层阶梯槽引导干冷空气南下并叠加在低层暖湿气流之上的有利背景条件下产生的,低空切变线是此次飑线过程的重要触发机制.在飑线成熟阶段,气流下沉速度极大值区在高(低)层与霰(雨水)混合比极大值区有很好的对应关系,水凝物粒子下落时对周围空气的拖曳作用是下沉气流形成的关键.雨水蒸发率影响飑线维持期间地面冷池的强度和分布,雨水蒸发率越大,地面冷池强度越强、范围越广;雨水蒸发率越小,地面冷池越弱,甚至消失.雨水蒸发率与地面风速也有很好的正相关性,增大雨水蒸发率可使地面风速增大,使模拟的地面最大风速更接近实况.%By using the 1°×1°NCEP/NCAR reanalysis data of 6 hours and mesoscale Weather Research and Forecasting (WRF) model,a strong squall line process in the Yangtze-Huaihe River Basin during 30 to 31 July,2014 was synoptically analyzed and numerically simulated.Results indicate that the squall line case occurred under the background that the mid-level stepped trough guided dry-cold air from the high-level superimposed on the low-level warm air,and the atmospheric instability enhanced and the unstable energy accumulated;the low level shear line prompted unstable energy release,which was an important triggering mechanism for the squall line.At the mature stage,the air maximum sinking velocity in high (low) layer has a good corresponding relationship with the graupel (rain) mixing ratio,and the hydrometeors' drag effect is the key to the formation of downdraft.Rainwater evaporation rate influences the strength and range of cold pool during the squall line maintenance period.The greater the evaporation rate of rainwater is,the stronger and wider the cold pool will be.The contrary is also true,or cold pool even disappears.Rainwater evaporation rate and surface wind velocity winds have a good positive correlation.The increasing rain evaporation rate can increase the wind speed on the ground,and the simulated maximum wind speed on the ground is also closer to the reality.

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