【摘要】 近10年来,太平洋年代际振荡(PDO)因其对全球气候系统的深远影响而得到广泛的研究。PDO指的足在太平洋的气候变率中具有类似ENSO空间结构但周期为10-30年的一种振荡,当北太平洋中部海面温度异常增暖(冷却)时,热带太平洋中部和东部以及北美沿岸常同时伴随有同等幅度的异常冷却(增暖)。总体而言,有两类观点分别认为PDO起源于确定的海气耦合过程或起源于大气的随机强迫。确定性起源论强调,一个海气耦合系统内部的物理过程可以提供一个正反馈机制以增强一初始扰动,及一个负反馈机制以促使振荡位相发生逆转;海洋环流的动力演变过程决定了振荡的时间尺度。随机性起源论则强调,因为大气活动没有一个特定的时间尺度,其时间尺度谱实际上对应于白噪音谱,所以大气对海洋的强迫是随机的;而海洋常在低频谱段有最大的响应振幅,其对应的周期约为十几年或几十年。作者试图系统性地理解PDO在观测、理论和数值方面的研究现状,从而为当前研究提供一个有用的背景性参考。更多还原

【Abstract】 The Pacific decadal and interdecadal oscillation (PDO) has been extensively explored in recent decades because of its profound impact on global climate systems. It is a long-lived ENSO-like pattern of Pacific climate variability with a period of 10-30 years. The general picture is that the anomalously warm (cool) SSTs in the central North Pacific are always accompanied by the anomalously cool (warm) SSTs along the west coast of America and in the central east tropical Pacific with comparable amplitude. In general, there are two classes of opinions on the origin of this low-frequency climate variability, one thinking that it results from deterministically coupled modes of the Pacific ocean-atmosphere system, and the other, from stochastic atmospheric forcing. The deterministic origin emphasizes that the internal physical processes in an air-sea system can provide a positive feedback mechanism to amplify an initial perturbation, and a negative feedback mechanism to reverse the phase of oscillation. The dynamic evolution of ocean circulation determines the timescale of the oscillation. The stochastic origin, however, emphasizes that because the atmospheric activities can be thought as having no preferred timescale and are associated with an essentially white noise spectrum, tne ocean response can manifest a red peak in a certain low frequency range with a decadal to interdecadal timescale. In this paper, the authors try to systematically understand the state of the art of observational, theoretical and numerical studies on the PDO and hope to provide a useful background reference for current research.更多还原