我国大气透明度系数的时间变化

作者在文献1]中探讨了我国大气透明度系数的空间分布及其主要影响因子。本文则探讨大气透明度系数的时间变化,特别是它的长期变化及其成因。结果发现:火山爆发可使大气透明度系数明显减小;由于人类活动影响,冬季大气透明度系数P_2、P_d有明显的减小趋势,P_2、P_d与用煤量等污染指标有很好的负相关。文中还对大气可降水含量的气候学推算方法进行了探讨。本文应用1820—1983年的地球自转变化率资料,分析出地球自转变化存在准44个月、准11年、准24年和准49年的周期。南方涛动指数的变化,大气活动中心位置的移动,赤道东太平洋海温的异常等,都能从地球自转速度变化思期中找到关系。已经发现,在地转长期(准24年和准49年周期)加(减)速时,南方涛动指数减弱(增强),大气活动中心向西北(东南)移动,非洲干旱区降水偏多(偏少);同时发现:在地转短期(准44个月周期)加(减)速时,赤道东太平洋海温降低(升高)。

THE TIME-VARIATION OF ATMOSPHERIC TRANSPARENT COEFFICIENTS IN CHINA

In this paper the time-variation of the atmospheric transparent coefficient (P2) and the transparent coefficients for aerosol and water vapour (pd and Pw) have been calculated and discussed. It has been found here that P., Observed at China's plain station, in summer, dec-rease an average 6.7%, 5.7% and 6.0% by the volcanic eruptions of Agung, Fuego and St. Helens respectively. The longterm changing trends of Pi, Pj become monotonously lower with the effects of the urban air pollution. Coherences between P2 and the coal-used amounts for several big cities suth as Beijing, are very obvious. The annual variation of the corresponding relations between P2 for Lanzhou City and the amounts of dust floating in the air and the day number of smoky fog occurring and the number of inversion occurring are all good. Finally, the characters of the daily variation for P2 over China have been discussed.In this paper, the fluctuations of quasi-44-month, quasi-11-year, quasi-24-year and quasi-49-year periods of the earth rotational rate are found from the analysis of its data of the years 1820?983. The anomalies of Southern Oscillation (SO) index, the motions of the atmospheric centres of action, the variations of sea surface temperature in the eastern equatorial pacific and the changes of long-range weather can be related with the periodic fluctuations of the earth rotational rate. It has been found that SO index becomes weaker (stronger), active centres of atmosphere move northwest-ward (southeast-ward) and annual precipitations increase (decrease) in Africa arid region, while the long-range earth rotational rate (fluctuations of quasi-24-year and quasi-49-year) speeds up (slows down). It has been also found that sea surface temperature is lower (higher) in the eastern equatorial Pacific, while the short-range earth rotational rate (quasi-44-mouth)speeds up (slows down).