Interannual Variations in Synoptic-Scale Disturbances over the Western North Pacific  

作　　者：Xingyan ZHOU Riyu LU Guanghua CHEN Liang WU 

机构地区：[1]State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China [2]University of the Chinese Academy of Sciences, Beijing 100049, China [3]Center for Monsoon System Research, I, stitute of Atmospheric Physics, Chinese Academy ofSciences, Beijing 100029, China

出　　处：《Advances in Atmospheric Sciences》2018年第5期507-517,共11页大气科学进展（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant Nos.41320104007,41475074 and 41475077)

摘　　要：The present study investigates the interannual variation of June-November synoptic disturbance activity over the western North Pacific（WNP） and its relationship with large-scale circulation for the period 1958-2014. Two leading modes of eddy kinetic energy for the disturbance variability over the WNP are obtained by EOF analysis, characterized by anomalous eddy kinetic energy over the subtropical WNP and around the Philippines, respectively. These modes explain a large portion of the interannual variance of synoptic disturbance activity over the WNP. Both are associated with lower-level cyclonic anomalies, but with different locations： over the subtropical WNP for the first mode and over the South China Sea for the second mode. Considering the impact of ENSO on synoptic disturbance activity over the WNP, we repeat the analyses after removing the effect of ENSO, which is simply defined as the components linearly regressed onto the Ni o3.4 index, and find similar results, suggesting that the leading modes and their relationships with large-scale circulation exist without SST effects.Further analyses suggest that the meridional shear of zonal winds caused by cyclonic anomalies is crucial for maintaining the leading modes through barotropic conversion.The present study investigates the interannual variation of June-November synoptic disturbance activity over the western North Pacific（WNP） and its relationship with large-scale circulation for the period 1958-2014. Two leading modes of eddy kinetic energy for the disturbance variability over the WNP are obtained by EOF analysis, characterized by anomalous eddy kinetic energy over the subtropical WNP and around the Philippines, respectively. These modes explain a large portion of the interannual variance of synoptic disturbance activity over the WNP. Both are associated with lower-level cyclonic anomalies, but with different locations： over the subtropical WNP for the first mode and over the South China Sea for the second mode. Considering the impact of ENSO on synoptic disturbance activity over the WNP, we repeat the analyses after removing the effect of ENSO, which is simply defined as the components linearly regressed onto the Ni o3.4 index, and find similar results, suggesting that the leading modes and their relationships with large-scale circulation exist without SST effects.Further analyses suggest that the meridional shear of zonal winds caused by cyclonic anomalies is crucial for maintaining the leading modes through barotropic conversion.

关 键 词：synoptic disturbance activity interannual variability leading mode barotropic conversion 

分 类 号：P732[天文地球—海洋科学]