摘要
针对长江下游典型涝年(1999、2016和2020年),通过全域功率谱分析和Lanczos滤波方法提取准双周振荡(QBWO)分量;并采用再分析资料进行同位相合成,揭示不同典型涝年共性特征及其各自的关键影响因子。结果表明:(1)1999、2016和2020年是长江下游地区最为典型的涝年,存在10—20 d显著的准双周振荡周期,且6—7月更为明显。(2)中、高纬度地区高层低频环流呈现扰动波列分布,有利于“两脊一槽”大尺度背景的维持和下游扰动增强,引起长江下游地区低频垂直运动变化,进而造成降水异常。低纬度地区准双周振荡是长江下游低频变化的另一来源,低层低频涡旋以10°N为轴对称分布,低频辐散风由中国南海指向长江下游地区,热带对流活动低频变化可通过低频大气环流影响长江下游降水。高、低纬度低频大气环流配合热源强迫存在相向运动,叠加低频水汽强烈辐合,为长江下游地区降水偏多提供有利条件。(3)3个长江下游典型涝年降水分布特征及其关键影响因子存在不同。1999年,西北太平洋上低频反气旋环流偏强、偏西,辐散风由中国南海指向长江下游地区,低频水汽来源为孟加拉湾和中国南海地区。2016年,对流层低层南、北低频环流系统耦合带呈现东北—西南走向,低纬度地区对流活动旺盛,向北传播的大气热源加热作用更强。2020年,中、高纬度地区垂直环流更完整,西北太平洋的东南水汽输送成为主要水汽来源。研究结果对认识长江下游地区夏季降水异常有重要意义。
Based on the ERA5 reanalysis data,the typical flood years of 1999,2016 and 2020 in the lower reaches of the Yangtze river are analyzed,and the quasi-biweekly oscillation component is extracted by the method of power spectrum analysis and Lanczos filtering.Common characteristics of different typical flood years are summarized,and their key influencing factors are respectively analyzed using in-phase composite study.The results are as follows:(1)1999,2016 and 2020 are the most typical flood years in the lower reaches of the Yangtze river,with a significant quasi-biweekly oscillation period of 10—20 d,especially from June to July.(2)In the middle and high latitudes,the low-frequency circulation is dispersed along the wave train disturbance,which is conducive to the maintenance of the large-scale background of"two ridges and one trough"and the enhancement of the disturbance in the lower reaches,causing precipitation anomalies by changing the low-frequency circulation and vertical movement over the lower reaches of the Yangtze river.The quasi-biweekly oscillation over the low-latitude region is another source of low-frequency in the lower reaches of the Yangtze river.The low-frequency circulation in 850 hPa is symmetrically distributed around 10°N,and the low-frequency divergent wind points from the South China Sea to the lower reaches of the Yangtze river.The low-frequency tropical convective activities can affect the precipitation anomaly in the lower reaches of the Yangtze river through vertical circulation.The interaction between circulations at the high and low latitudes,combined with the thermal forcing and the strong convergence of low-frequency water vapor movement,provides a favorable condition for anomalous precipitation in the lower reaches of the Yangtze river.(3)The distribution characteristics and key influencing factors of precipitation in the three typical flood years in the lower reaches of the Yangtze river are obviously different.In 1999,the low-frequency anticyclone circulation over the western
作者
陈蔚
刘梅
杨华栋
李杨
CHEN Wei;LIU Mei;YANG Huadong;LI Yang(Jiangsu Meteorological Observatory,Nanjing 210008,China;Nanjing Joint Institution for Atmospheric Sciences,Nanjing 210008,China)
出处
《气象学报》
CAS
CSCD
北大核心
2023年第3期393-415,共23页
Acta Meteorologica Sinica
基金
国家“重大自然灾害”重点专项(2017YFC1502000)
江苏省气象局重点项目(KZ202101)
江苏省气象局青年项目(KQ202101)。
关键词
准双周振荡
典型涝年
降水异常
长江下游
北半球夏季
Quasi-biweekly oscillation
Typical flood years
Precipitation anomaly
Lower reaches of the Yangtze river
Boreal summer
