ENSO对冬季北太平洋水汽输送及大气河的影响

利用1979-2016年ERA-Interim再分析资料,分析了ENSO对冬季北太平洋地区水汽输送特征的影响,包括整层水汽含量、整层水汽输送及其散度和大气河频率。结果表明,在El Ni1o年冬季,东北太平洋地区的气旋式环流异常增强了自副热带太平洋向北美西海岸的水汽输送,导致区域性的水汽辐合与辐散异常;La Ni1a年冬季的水汽输送特征与厄尔尼诺年大致相反。根据尺度分解的方法,对水汽输送及其散度的异常成因进行分析,得到结论如下:除El Ni1o年黑潮及其续流区外,ENSO年冬季北太平洋的水汽输送异常主要由环流异常导致;水汽输送散度异常则主要由环流异常的散度、气候态比湿的经向梯度和异常比湿的纬向梯度三部分决定。此外,El Ni1o年冬季北太平洋大气河频率分布的向极弯曲增强,分布更加集中;而La Ni1a年冬季大气河频率分布更加分散,纬向跨度减小,经向跨度增加。

The impact of ENSO on vapor transportation and atmospheric rivers over North Pacific during winters

The impact of ENSO on the vapor transportation characteristics over the North Pacific in boreal winters during 1979 to 2016 was investigated with ERA-Interim reanalysis data, including the Integrated Water Vapor (IWV), Integrated Vapor Transport (IVT) and its divergence, as well as the Atmospheric River (AR) frequency. During El Niño boreal winters, the vapor transportation from the subtropical Pacific to the west coast of North America is intensified with cyclonic circulation anomalies over the Northeast Pacific, causing corresponding regional convergent and divergent anomalies. During La Niña boreal winters, the characteristics of vapor transportation are roughly opposite to those of El Niño cases. Analysis of contributing factors on IVT and its divergence is performed based on the scale decomposition method, and the conclusions are as follows: IVT anomalies in ENSO winters over the North Pacific are primarily decided by the circulation anomalies except for the Kuroshio-Oyashio Extension (KOE) region in El Niño winters. IVT divergence anomalies are mainly contributed by the divergent circulation anomalies, the meridional gradient of climatological specific humidity, and the zonal gradient of anomalous specific humidity. Furthermore, the AR distribution is more centralized and anomalously shifted poleward in El Niño winters, while more decentralized with a wide meridional and limited zonal range in La Niña winters over the North Pacific.