夏季青藏高原移动性对流系统与中国东部降水的相关关系

利用国际卫星云气候计划提供的1985-2002年共18年的MCSs路径跟踪资料、 NCEP/NCAR逐月再分析资料和中国138个地面常规观测站资料,分析了夏季起源于青藏高原地区的移动性MCSs的主要时空分布特征,探讨了青藏高原MCSs与中国降水的关系.通过对MCSs爆发异常强弱年高度和风差值场的分析,概括出青藏高原MCSs影响中国降水的可能机制.结果表明:夏季青藏高原移动性MCSs主要生成于青藏高原东南部,其爆发时间具有明显的日变化特征,它们能够传播到我国中东部及南亚许多地区;夏季MCSs对我国降水具有重要影响,它们与中国夏季降水的相关系数分布以4条正、负相间的东西向分布带的形势存在,从南到北依次为"- - ",这与我国夏季降水带的变化形势非常一致;南亚高压、西太平洋副热带高压和东北冷涡的强度、位置变化与高原MCSs生成的多少密切相关,并通过它们对我国夏季降水带的分布造成重要影响.

The Relationship between Mobile Mesoscale Convective Systems over Tibetan Plateau and the Rainfall over Eastern China in Summer

The relationship between mobile MCSs over Tibetan Plateau and the summer rainfall over China is studied by using the Deep Convection Tracking Database from ISCCP,reanalysis data from NCEP/NCAR,precipitation data from 138 stations.The spatial and temporal distribution characteristics of mobile MCSs over Tibetan Plateau are also analyzed.The paper describes the possible mechanism of mobile MCSs over Tibetan Plateau influencing the rainfall in China by comparing the differences between the geopotential heights and wind fields for the strong and weak years of mobile MCSs generation over Tibetan Plateau.The results show that most of the mobile MCSs over Tibetan Plateau in summer come from southeast of Tibetan Plateau,their generation times have evident diurnal cycle characteristic,and they could move or propagate to most of Chinese east-middle and South Asia region.It is found that there is significant correlation between mobile MCSs over Tibetan Plateau and the rainfall over China.The distribution of correlation coefficient presents to be four zonal bands,which is \!-+-+" from south to north,just like the regular pattern of rainbands over China.The intensity of South Asia High,West Pacific Subtropical High and Northeast Cold Vortex are suggested to play their roles on the environment,thus effecting the generation of mobile MCSs over Tibetan Plateau and rainfall over China.