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气象:2017,43(1):21-33
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一次梅雨锋暴雨的中尺度对流系统及低层风场影响分析
(1.国家气象中心,北京 100081;2.国家气候中心,北京 100081)
Analysis on Mesoscale Convective System and Impact of Low Level Wind in a Meiyu Heavy Rainfall Event
(1.National Meteorological Centre, Beijing 100081;2.National Climate Centre, Beijing 100081)
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投稿时间:2016-04-10    修订日期:2016-08-30
中文摘要: 本文利用常规气象观测资料,地面自动站加密观测资料和FY 2D、FY 2E卫星云图以及NCEP 1°×1°的FNL分析资料、EC 0.25°×0.25°的细网格模式数据等,对2015年6月15—18日梅雨锋暴雨过程的中尺度对流系统(MCS)活动特征、对流层低层风场对MCS发展的影响以及梅雨锋暴雨的垂直环流特征等进行了研究,结果表明:天气尺度梅雨锋上叠加的MCS的产生及向下游移动,以及其在安徽中部到江苏南部正涡度带作用下的发展增强,造成了江苏南部的局地强降水。强降水与中尺度低空急流核的位置吻合较好。在垂直方向上,高空急流入口区右侧与低空急流核左前方叠加,高低空急流耦合作用明显。在降水过程中,对流层低层具有较强的垂直风切变,有利于垂直涡度的增强和MCS的发展。对流层低层的垂直风切变也有利于不同源地的水汽在梅雨锋区汇集。梅雨锋北侧的干冷空气在对流层低(中)层以东北(西北)路径向锋区移动。南侧的暖湿气流沿西南路径移动、抬升,接近锋区后质点在上升过程中逐渐转向东移,在高空急流的抽吸作用下,快速向东流出,近地面层空气存在跨锋面环流。梅雨锋系统垂直方向上的次级环流是高层风场强烈辐散以及空气运动过程中质量补充和循环的结果。
Abstract:By using the data of conventional observation and surface automatic station observation, FY 2D and FY 2E satellite cloud images, NCEP 1°×1° FNL analysis data and EC 0.25°×0.25° fine grid model data, the evolution features of mesoscale convective system (MCS), low tropospheric wind impact on MCS development and vertical circulation structure of Meiyu front in a Meiyu heavy rainfall event that happened during 15-18 June 2015 were studied in this paper. It was found that the local heavy rainfall in south of Jiangsu Province was caused by emergence and downstream movement of a series of MCSs along synoptic scale Meiyu front and their strengthening through the positive vorticity belt in central Anhui and southern Jiangsu. There was good agreement on locations between the heavy rainfall and low level jet (LLJ) core. In vertical direction, the right side of high level jet (HLJ) was overlaid on the left front side of LLJ core resulting in obvious coupling between the two systems. During the heavy rainfall, there was both strong vertical shear in low tropospheric horizontal wind and distinct inhomogeneous distribution of upward motion in southern Jiangsu which were favorable for the enhancement of vertical vorticity and development of MCS.High vertical wind shear in low troposphere was also helpful for merging water vapor from different moisture sources along Meiyu front.The dry cold air in the north of Meiyu front moved close to the front zone through a northeast (northwest) track in low level (middle level) troposphere. And warm moisture air in the south of Meiyu front approached the front zone and went upward by a southwest way. As the warm moisture air particles approached Meiyu front zone, they turned to move eastward gradually and flowed away quickly through the pumping effect of HLJ.There was cross front motion for near surface air. The vertical secondary circulation of Meiyu front was induced by strong high level divergence and supplement and circulation of mass during the moving process of atmosphere.
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基金项目:中国气象局预报预测核心业务发展专项(CMAHX20160301)、国家气象中心预报员专项(Y201504和Y201606)共同资助
引用文本:
杨舒楠,路屹雄,于超,2017.一次梅雨锋暴雨的中尺度对流系统及低层风场影响分析[J].气象,43(1):21-33.
YANG Shunan,LU Yixiong,YU Chao,2017.Analysis on Mesoscale Convective System and Impact of Low Level Wind in a Meiyu Heavy Rainfall Event[J].Meteor Mon,43(1):21-33.