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本文在论证所谓“北方涛动”存在性的基础上,分析了这一现象与经典的“南方涛动”的关系和它们的性质,提出了”低纬度涛动”的概念。 研究发现,这两类振荡在低频域内具有相同的振荡频率,处于同一振荡系统内。实质上反映了印度洋和太平洋低纬地区三个主要活动中心——赤道低压和南、北太平洋副热带高压的年际变化之间的联系。 这个振荡系统,在气压场上表现为,横跨赤道南北各约30个纬距的东西向的“跷跷板”(seesaw)现象,且有以赤道为界的两个分量,即南方涛动和北方涛动。在温度、湿度场和低层大气稳定度场上,主要表现为热带太平洋上高温、高湿和强不稳定与低温,低湿和弱不稳定的交替出现;在云量场上表现为主要对流区的东西向位移;在海面温度场上为赤道太平洋增暖和降温的交替出现。它们之间通过热力和动力过程耦合起来,组成了全球热带海洋大气系统的振荡,这是低纬度大气环流年际变化的一个基本特征,我们称它为“低纬度涛动”。 分析表明,它的振荡周期平均约为40个月。为区别于40—60天的热带低频振荡,这一年际尺度的振荡可称为“甚低频振荡”。 作者用全球热带海平面气压第一特征向量的时间系数定义“低纬度涛动指数”,它能客观地同时描写气压场上振荡的两个分量,以及温度、湿度、云量和低层大气稳定度等
On the basis of demonstrating the existence of the so-called “northern oscillation,” this paper analyzes the relationship between this phenomenon and the classic “Southern Oscillation” and their nature and puts forward the concept of “low-latitude oscillation.” It is found that the two types of oscillations have the same oscillation frequency in the low frequency range and are in the same oscillation system. It essentially reflects the connection between the equatorial low pressure and the interannual variations of the South and North Pacific subtropical highs at the three major centers of activity in the Indian Ocean and the Pacific low latitudes. This oscillatory system behaves in the pressure field as an east-west seesaw phenomenon spanning about 30 latitudes north and south of the equator and has two components that are bounded by the equator, namely, the Southern Oscillation and the North Oscillation. In the field of temperature, humidity and low-level atmospheric stability, the main manifestations are the alternation of high temperature, high humidity and strong instability with low temperature, low humidity and weak instability in the tropical Pacific Ocean; the main convection area in the cloud field East-west displacement; in the sea surface temperature field for the equatorial Pacific warming and cooling alternately. They are coupled by thermal and dynamical processes and form the oscillation of the global tropical oceanic atmosphere. This is an essential feature of the interannual variation of low-latitude atmospheric circulation, which we call “low-latitude oscillation.” Analysis shows that it oscillates on average about 40 months. To distinguish tropical low-frequency oscillations from 40-60 days, this interannual oscillation can be called “very low frequency oscillation”. The authors use the time coefficient of the first eigenvector of the global tropical sea level pressure to define “low-latitude Oscillation Index,” which objectively simultaneously describes two components of the oscillations in the barometric pressure field, as well as temperature, humidity, cloud cover, and low-level atmospheric stability Wait