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利用气象常规观测资料、自动站加密资料、NCEP 1°×1°再分析资料以及卫星资料,对2015年4月1日和8月2日黄河中游地区的两个MCC结构特征进行了对比分析.结果表明:(1)春季MCC形成阶段发展快、成熟期慢,具有前向传播的特点,降水较为稳定,雨团移动慢,暴雨主要由降水持续时间长造成;盛夏MCC形成慢、发展迅速,为后向传播,以对流性降水为主,雨团移动性强,暴雨主要由短时强降水造成;在不同生命阶段,小时最大雨量出现在不同区域.(2)春季MCC生成于整层为西南气流、大气斜压性较强的背景下,散度场表现为垂直的空间结构特征,而盛夏MCC生成于500 hPa平直西风环流、200 hPa反气旋前沿、大气斜压性弱的背景下,散度场为倾斜的空间结构;在它们的后期发展过程中,水汽、热力和动力结构均存在显著差异.(3)两个MCC均形成发展于条件不稳定、对流不稳定和对称不稳定共存的区域,但MCC的形成与不稳定度和不稳定能量大小有关,它们的发展则与不稳定能量的持续增大和对称不稳定度持续增强关系更密切,盛夏尤其如此.(4)中高层干冷空气侵入、曲率涡度造成的整层辐合上升运动持续加强以及对称不稳定是春季MCC的重要触发机制,而切变涡度引起的低层中尺度辐合上升、对称不稳定和重力波传播是盛夏MCC的主要触发机制.“,”Based on observational data,encryption data of automatic station,NCEP reanalysis and satellite data,the structure characteristics of MCC occurred on 1 April and 2 August 2015 over the Yellow River midstream was comparatively analyzed.The results are as follows:(1) The formation stage of spring MCC was fast and mature was slow.It has forward propagation feature.Precipitation was stable,rain clusters moved slowly,and the rainstorm was mainly caused by long duration of precipitation.While the formation stage of summer MCC was slow and mature was rapid.It has backward propagation feature.It was mainly convective precipitation,rain clusters were mobility,and heavy rainfall mainly caused by short-period strong precipitation.Maximum hourly rainfall occurred in different areas at different stages of their life time.(2) The spring MCC was formed under the background of the southwest airflow at the whole layers and strong baroclinic property.The spatial structure characteristics of the divergence field was vertical.But the summer MCC was formed under the background of flat westerly circulation on 500 hPa,front of anticyclone on 200 hPa,and the weak baroclinic property.The spatial structure characteristics of the divergence field was declining.In their later development,there were significant differences in water vapor,thermal and dynamic structure.(3) Two MCC were formed and developed in the coexistence region of conditional,convective,and symmetric instability.The formation of MCC was related to the instability and the unstable energy,but their development were more closely related to the continuous increase of the unstable energy,and continuous enhancement of symmetric instability,especially in midsummer.(4) Intrusion of dry cold air at middle and upper layer,continuous strengthening of convergent ascending motion caused by the curvature vorticity at the whole layers,and symmetric instability were important triggering mechanisms of MCC in spring.Mesoscale convergent ascending motion at lower layer caused by shear vorticity,symmetric instability,and gravity wave propagation were the main triggering mechanisms of MCC in midsummer.