西北太平洋波候与大气涛动的联系

Relationship between atmospheric oscillation and wave climate in the western Pacific

利用ECMWF 1958-2001年44a的ERA-40海浪再分析资料计算了西北太平洋海域(0°～45°N,99°～160°E)月平均有效波高(SWH)、平均周期(T)与北太平洋模态指数(NPI)、太平洋年代际振荡(PDO)和多变量ENSO指数(MEI)等大气涛动之间的时间和空间的相关性,重点探讨了NPI对北半球西太平洋波候(SWH和T)的影响。结果表明:NPI、PDO和MEI均与SWH和T有显著的相关性;NPI与SWH和T呈现正相关性,NPI超前SWH和T半年左右正相关最强,最强的相关海域位于日本和菲律宾以东洋面;NPI还存在3～5a、8～9a和13～15a的年际和年代际周期变化;NPI高指数且PDO负位相或MEI负位相均使得SWH和T增大;MEI冷位相且叠加PDO负位相时也利于SWH和T增大。NPI影响西北太平洋波候的可能机制是:NPI处于低(高)指数时,阿留申低压加深(减弱)且位置偏东(西),北太平洋西风带海面风速急流出现(消失),太平洋副热带东北信风大值区东移(西移),西北太平洋海域信风减弱(加强),西北太平洋海域有效波高和平均周期随之减小(增大)。中、东太平洋西向传播的涌浪对西北太平洋海域波侯有重要影响。

In this study the temporal and spatial correlations of atmospheric oscillation in terms of the SWH,the T and North Pacific Index（NPI）,the Pacific Decadal Oscillation（PDO）,and MEI in the western North Pacific（0°— 45°N,99°—160°E）are investigated by using ERA-40wave re-analysis data from 1958to 2001,with a focus on impacts of the NPI on SWH and T.Results show that NPI,PDO and MEI are all closely related to SWH and T;NPI and SWH as well as Tshow a positive correlation,which is most evident around half a year in the east ocean of Japan and Philippines.NPI also shows inter-annual and decadal periodic variations of about 3-5a,8-9a,and 13-15a.High NPI and negative phase of PDO or MEI will lead to the increase of SWH and T.Cold phase of MEI and negative phase of PDO is also beneficial for the increase of SWH and T.The possible mechanisms through which NPI influences the wave climate in the western North Pacific are：When the NPI is low（high）,Aleutian low will be deepened（weakened）and located more easterly（westerly）.As a result,the jet stream in westerlies appears（disappears）,the trade wind in western Pacific Ocean is weakened（strengthened）,and wave height decreases（increases）.