本文利用1993年—2012年AVISO卫星高度计融合数据,识别和追踪了北太平洋海域(100°E—77°W,0°N—70°N)20年的中尺度涡.统计分析了北太平洋中尺度涡的生命周期、振幅、移动速度等属性特征、空间分布和运动特征、季节、年际和年代际的变化趋势及其与ENSO的关系.结果表明:北太平洋中尺度涡的平均寿命为6.9周,平均振幅为8.44 cm,平均速度为6.4 cm/s;随着纬度的增加,反气旋涡的生命周期和振幅差异较大,气旋涡差异较小,涡旋的移动速度随纬度的增加逐渐减少.在空间分布上,日本东部的黑潮延伸区、加利福尼亚海岸和阿拉斯加湾是涡旋的高发区,其中黑潮延伸区分布最为密集;涡旋大多数向西运动,只有少数涡旋向东传播,移动过程中反气涡旋表现为向赤道方向偏移,气旋涡向极地方向偏移,且具有明显的非线性特征.在季节、年际尺度上,春季和夏季是涡旋高发的两个季节,秋季和冬季生成的涡旋相对最少,在加利福尼亚沿岸涡旋的季节差异较明显;涡旋数量的年际变化与ENSO事件具有明显的相关性,1993年—2002年厄尔尼诺年生成的涡旋较多,而拉尼娜年生成的涡旋较少,2003年—2012年则是厄尔尼诺年生成的涡旋较少,而拉尼娜年生成的涡旋较多.

The North Pacific Ocean has a complex circulation system and is thus sensitive to global atmospheric and oceanic changes. Mesoscale eddies are widely found in this region. Research on the distribution characteristics and motion features of mesoscale eddies is very important in explaining the energy change and air-sea interaction in the region. In this study, the merged altimeter data obtained from AVISO are used to identify and trace the mesoscale eddies in the North Pacific (100°E—77°W, 0°N—70°N) from 1993 to 2012. The attribute characteristics (such as amplitude, radius, and speed), spatial distribution, and transmission characteristics are statistically analyzed. The seasonal, interannual, and decadal variabilities are also studied. The SLA-based method is used to identify mesoscale eddies based on the outermost closed contour of sea level anomalies. This algorithm is widely used because of its high accuracy. The tracking method applied is a combination of the nearest distance method and the similarity-based method. If no trace is observed for two weeks, the eddy is considered to have disappeared. The tracking process needs to last at least four weeks.The average amplitude and speed of the eddies in the North Pacific are 8.44 cm and 6.4 cm/s, respectively. An eddy can continue for about 6.9 wk. Unlike those of cyclones, the amplitude and lifetime of anticyclones obviously change in different zonal bands. As latitude increases, the propagation speed of eddies gradually reduces. Eddies are abundant in California, the Gulf of Alaska, and especially in the Kuroshio Extension. Most of these eddies propagate west nonlinearly. Anticyclones are prone to poleward deflections, whereas cyclones are prone to equatorward deflections. Eddies occur frequently in spring and summer and occasionally in autumn and winter. Seasonal variations are apparent in California. The interannual variabilities of the number of eddies are closely related with the ENSO phenomena. In 1993 to 2002, the number of eddies was positively relative to the EMI index, but in 2003 to 2012, it was negatively relevant. We focused on the spatio-temporal distribution characteristics of mesoscale eddies in the North Pacific and analyzed the distribution differences from 1993 to 2002 and from 2003 to 2012. The differences were mainly observed in the subtropical countercurrent area and in the open ocean in the Northeast Pacific. However, the mechanisms of eddy genesis and the causes of the differences in temporal and spatial distribution must be analyzed with a physical ocean model. This aspect should be implemented in future research.