北半球500百帕环极气流的气候振动

本文根据北半球500百帕图上552位势什米等高线所包围面积的大小，计算了1951—1980年历年逐月环极气流指数。通过对近30年来环极气流指数的分析，发现环极气流不但有明显的季节变化，而且还有2—4个月、5年、19—20年的周期性振动。在1951—1980年的30年中，五十年代环极气流收缩，六十年代环极气流扩张，七十年代以来则一直在平均值附近振动。环极气流指数与我国的气温和降水均有密切关系。当环极气流扩张（收缩）时，我国气温偏低（偏高）；降水在冬春和初夏季节偏少（偏多），在盛夏和秋季偏多（偏少）。这些结果可以用来很好地解释过去30年气候形成的原因。

The Climate Oscillations of the Circumpolar Circulation at 500 hPa in the Northern Hemisphere

In this paper, the climate oscillations of the monthly circumpolar circulation index during 1951—1980 defined as the area enclosed 5520 m, isohypse are studied. It has been found that the circumpolar circulation index not only may easily undergo seasonal variations but also may vary with periodicity of oscillation such as 2—4 months, 5, and 19—20 years. During the period of 30 years from 1951 to 1980, the circumpolar circulation was contracted in the 1950s and expanded in the 1960s, However, during the 1970s, it kept oscillating in the vicinity of the average value. There exists a close relationship between the circumpolar circulation index and the surface air temperature or precipitation in China. When the circumpolar circulation is expanding (contracting), the surface air temperature will decrease (increase) and the precipitation will decrease (increase) in winter, spring and early summer and increase (decrease) in midsummer and autumn. These results can be used to explain the cause of climate change during the past thirty years