摘要
利用NCEP 1°×1°资料、加密自动站降水资料及FY2C红外云图资料对2012年7月6-9日及2011年7月4—6日期间发生在四川盆地并造成强降水的4次相似MCC过程的卫星云图特征进行了对比分析,探讨了MCC生成及发展旺盛期的环流场特征,进一步诊断了MCC发展过程的水汽、热力以及动力机制(垂直散度通量、干位涡).研究表明:2例过程中4次MCC的第1、3个是在进入盆地的卷云羽上的对流云团中生成和发展,2、4个MCC是在残留云系上的对流云团中生成、发展和合并,形成过程中均表现为亮温降低、面积增大,川西高原及MCS周围云系逐渐减弱的特点.在强且持续的孟湾水汽输送和不稳定层结条件下,对流层低层西南涡区辐合抬升造成强烈的散度通量辐合向上输送与高层辐散耦合是MCC发展持续的动力机制,且850 h Pa垂直散度通量辐合区与MCC持续区域及观测的地面强降水落区具有良好的时空对应关系.中高纬的高值位涡具有向南向下延伸,低纬低层的低值位涡具有向上向北传播的特点.当干冷空气与较强暖湿气流相交汇时,850h Pa急流左前侧的西南涡区强烈的风场切变与辐合导致强上升运动,触发对流不稳定能量释放,激发MCC云团,造成强降水.
Using the NCEP 1 °× 1 ° data, encrypted automatic stations data of Sichuan Province and FY2C infrared cloud image data, characteristics of satellite cloud pictures for four similar MCC process on July 6-9, 2012 and July 4--6,2011 occurred in the Sichuan Basin which caused heavy rain were analyzed.On this basis, atmospheric circulation characteristics of the creation and development of MCC had been discussed and the moisture, heat and power mechanism on the development process of MCC had been further studied by diagnostic methods （vertical divergence flux,dry potential vorticity）.The results showed that during the two cases, the first and third MCC generated and developed in the convective clouds for cirrus plume in the basin, the second and forth MCC generated ,developed and merged in the remaining structures convective clouds, all performed bright temperature decrease, area increases, and surrounding structures would gradually diminish on the plateau of Western Sichuan and MCS in the forming process.Strong and sustained water vapor transport from the bay of Bengal and instability stratification conditions, low-level troposphere for southwest vortex area uplift caused strong vertical divergence flux convergence upward transportation and high-level divergence was corresponding to the dynamic mechanism for MCC development and continuous, 850 hPa vertical divergence flux convergence zone had good corresponding relationship of time and space with MCC area and observation of ground rain fall area. High value potential vorticity from high latitude extend to the south and low latitude,low value from low-level had the characteristics of upward spread north.when the dry cold air intersected with warm moist air, 850 hPa strong wind shear and the convergent in the southwest vortex area of the left side before the jet resulted strong upward movement,triggered the release of convection instability energy,inspired MCC cloud and caused heavy rain.
出处
《云南大学学报（自然科学版）》
CAS
CSCD
北大核心
2016年第4期563-574,共12页
Journal of Yunnan University(Natural Sciences Edition)
基金
西南区域强降水预报创新团队
中国气象局预报员专项(CMAYBY2013-058)
短历时强降水客观预报技术(CMAGJ2013Z04)
关键词
MCC
强降水
垂直散度通量
干位涡
MCC（ mesoscale convective complexes）
heavy rains
vertical divergence flux
dry potential vorticity
