摘要
利用1961年1月至2012年12月太平洋年代际振荡指数(Pacific Decadal Oscillation Index,PDOI)、NCEP/NCAR再分析环流数据集和江苏13个市级观测站点的夏季雷暴日数观测资料,分析了PDO与江苏夏季雷暴日数年代际变化的联系及其可能原因。结果表明,春季PDOI与江苏夏季雷暴日数均具有明显的年代际波动,两者年代际变化的趋势几乎相反:20世纪70年代中期以前和2006年以来,均对应PDO的冷位相和江苏夏季雷暴的多发时期,而20世纪70年代中后期至21世纪初,PDO处于暖位相期,江苏夏季雷暴频数明显偏少。PDO冷期,欧亚大陆和西太平洋地区夏季海平面气压和500 h Pa位势高度呈现大范围的负距平环流异常,近地面亚洲热低压显著增强,对流层中层极涡易于偏向亚洲区,青藏高原北部亚洲中部大槽加深,西太平洋副热带高压偏弱偏东,印缅槽偏强。在此环流形势下,夏季江淮流域上空低层有较强的异常西南水汽输送,江苏上空低层偏湿、中层偏干,上干下湿的垂直分布有利于对流不稳定的产生。同时,PDO冷期,江苏上空低层辐合、高层辐散,有明显的上升运动,并具有较强的低层垂直风切变,为夏季雷暴的发生、发展提供了有利的气象条件;PDO暖期,则情况相反。PDO作为一种比较稳定的年代际尺度的气候变率强信号,其对应的环流异常为雷暴现象这类中小尺度天气现象的发生、发展提供了重要的环境背景和气象条件。
The monthly Pacific Decadal Oscillation index（PDOI）,NCEP/NCAR monthly reanalysis dataset,and thunderstorm days data recorded by 13 stations in Jiangsu for the period of 1961-2012 are used to investigate the relationships between PDO and summer thunderstorm days（STDs）in Jiangsu and the possible cause.The results show that spring PDOI and STD in Jiangsu both are characterized by interdecadal variations,and they are just out of the phase.Before the mid-1970 s and since 2006,PDO was in the negative phases and STDs in Jiangsu were more than the climatic average.However from the mid-late-1970 s to early in the 21 th Century,PDO was in its warm phase,and thunderstorm poorly happened in Jiangsu in summer.During the cold phase of PDO,there are extensive negative anomalies of both sea level pressure and 500 h Pa height over the Eurasian continent and western Pacific in summer.Associated with this,the Asian low pressure behave stronger,the polar vortex in troposphere tends to move towards the Asian region,and the trough to the north of the Qinghai-Xizang Plateau in central Asian is intensified.Moreover,the western Pacific subtropical high is weaker and eastward than the normal.The India-Burma trough strengthens obviously.In the control of the anomalous circulation,there is anomalously stronger transport of water vapor from the southwest at the low level of the troposphere over the Yangtze-Huaihe region.The mid-level air over Jiangsu turns to be drier while the low-level turns to be wetter,which contribute to unstable air layer and strong convective activity.It is also found that the anomalous lowlevel convergence and the anomalous upper-level divergence is observed,accompanied by ascending anomalies over Jiangsu.Meanwhile the vertical wind shear is abnormally enhanced in the lower troposphere when PDO is in its cold phase.All of this contributes to the development of thunderstorm in summer.And it is vice versa during the PDO warm phase.As a stably strong signal of interdecadal climate variability,the anomalous circulation associated PDO phenomena provides important environment and meteorological conditions for some kind of meso-and small-scale system events such as thunderstorm.
出处
《高原气象》
CSCD
北大核心
2016年第4期1015-1026,共12页
Plateau Meteorology
基金
公益性行业(气象)科研专项(GYHY201106017)
江苏省科委科技支撑计划社会发展项目(BE2011818)
关键词
太平洋年代际振荡
夏季雷暴日数
年代际变化
反位相
Pacific Decadal Oscillation
Summer thunderstorm days
Interdecadal change
Out of the phase
作者简介
陈圣劼（1987-），女，江苏如东人，硕士研究生，主要从事季风与海陆气相互作用研究．E-mail：chenshengjieshiz@163．com
通讯作者：孙燕．E-mail：jsshqxtsy@sina．com
