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作 者:施宁[1] 布和朝鲁[2] 纪立人[2] 王盘兴[1]
机构地区:[1]南京信息工程大学大气科学学院,南京210044 [2]中国科学院大气物理研究所灾害性气候研究与预测中心
出 处:《气候与环境研究》2008年第4期434-445,共12页Climatic and Environmental Research
基 金:中国科学院大气物理研究所创新基金领域前沿项目IAP07120;国家重点基础研究发展规划项目2006CB403601
摘 要:针对2008年初1月17~23日我国南方地区雨雪低温过程,分析了其中期演变特征及其可能机理。这次过程中:1)西太平洋副热带高压在其前期异常状态的基础上,在对流层低层演变为“内凹外凸”结构,并在我国长江中下游附近形成切变线,从而造成了这次雨雪过程;2)在对流层上层,源自北非的Rossby波能量在副热带和中纬度地区向下游频散,同从乌拉尔山地区向南频散出的Rossby波能量在帕米尔高原及中亚地区汇合,共同引起该地区气压槽的加深。它使对流层低层西太平洋副高在其西部向内凹陷。另一方面,在对流层中层,Rossby波能量沿副热带急流传播,最终引起西太平洋副高向西南方向伸展。西太平洋副热带高压的“内凹外凸”演变特征的主要原因是来自上游地区的Rossby波活动,并非热带西太平洋对流异常活动;3)亚洲北部冷高压沿高原东侧伸入我国东部地区是我国南方地区低温过程的主要原因。Medium-range evolution features and the possible mechanism for the rainy and snowy weather process over South China during January 17 to January 23,2008 are investigated.It is shown that: 1) With its anomalous state formed previously,the western Pacific subtropical high evolves into the so-called "concave-inner and protruding-outer" structure in the lower troposphere during this period.Such a structure constitutes a distinct shear line straddling over the middle and lower reaches of the Yangtze River,which is primarily responsible for the rain and snow process.2) In the upper troposphere,Rossby wave energy emanating from North Africa disperses downward both in the subtropical and mid-latitude region.The Rossby wave packets from upstream mid-latitude and subtropical region converge around the Pamir plateau and central Asia,showing a deepening pressure trough there.On one hand,its eastward expansion and temporary movement causes the concave-inner structure for the west part of the West Pacific subtropical high in the lower troposphere;On the other hand,in the middle troposphere,Rossby wave energy emanates along the subtropical jet,and eventually leads to the southwestward expansion of the West Pacific subtropical high.Therefore,the formation of the "concave-inner and protruding-outer" structure of the West Pacific subtropical high could be attributed to the upstream Rossby wave activity,rather than the anomalous convective activity over the tropical western Pacific.3) The invasion of the cold high system of North Asia along the eastern slope of Tibetan Plateau is mainly responsible for the low temperature weather over South China.
分 类 号:P448[天文地球—大气科学及气象学]
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