正压海洋对中纬西风响应的解析解及讨论

采用中纬度正压准平衡海洋模型,解析求解了其对时变风场强迫的响应,主要结论有: 在时刻t=0和T／2 (T为风场变化周期),在β通道中线上该风场强迫出明显的海洋流场,而在时刻t=T／4和3T／4,虽无大气风场强迫,但仍有较弱的海洋流场。在β通道西边界附近的海洋响应为一对由气旋性和反气旋性曲率构成的涡旋偶,这与在日本本州岛以东、以南海洋流场的EOF模态相像。该解析解中时变风场与流场响应的频率完全相同,但两者存在有位相差,这表明流场响应要滞后于风场异常。该海洋响应的性质属准平衡涡旋波。该解析解能够大体反映时变风场强迫下中纬度北太平洋上层海洋流场的响应,且较先前的结果要优。

Barotropic ocean model forced by mid latitude time varying wind

The barotropic quasi equilibrium ocean model forced by mid latitude time varying wind field was established and its analytic solutions obtained. The solutions show that obvious oceanic flow anomalies can be forced on β　channel centerline at t=0 and t=T／2 (where T is the varying period of wind field), which is similar to observations. Around t=T／4 and t=3T／4, although the forcing of wind disappears, oceanic flow anomalies still exist for inertia. It is further found that obvious flow anomalies with cyclone and anticyclone show itself at the western boundary, which is similar to the spatial pattern of the first leading mode of the oceanic flow in the southeast of Honshu Island in Japan. In analytic solutions, the fluctuation frequency of the oceanic flow is the same as its forcing wind field except for a fixed phase difference, suggesting that the responding flow lags to the wind anomalies. The nature of the flow anomalies is quasi equilibrium vortex wave. The model established in this paper is applicable in many cases for considering time varying wind, and its analytic solutions can reflect the upper flow anomalies in the mid latitude North Pacific to some extent.