观测序列的不均一性对估算北京和上海的平均温度与极端温度变化趋势的影响

根据北京和上海气象观测站的详细历史资料，修正了两站逐日温度序列的不均一性，并分析这种不均一性对长期气候变化趋势估计的影响。对北京序列，不同时期的主要修正幅度在－０．３３－０．６℃；对上海序列则为－０．３３－０．３℃。从逐日序列计算出年平均温度和年极端温度序列，并把修正之前和修正之后的序列趋势进行比较，修正之后的两站年平均温度序列自２０世纪初起呈现出０．５℃／百年的变暖趋势，自２０世纪６０年代起这一趋势增强为２．０℃／百年。相比之下，上海的未修正资料显示出两倍于此的趋势；北京的未修正资料几乎没有长期趋势，而对近期的变暖趋势则高估了５０％－３０％。北京温度序列在２０世纪４０年代至７０年代呈变冷趋势，极端事件的频率降低；此后又呈变暖趋势，极端事件的频率增加。上海温度极端事件的变化趋势基本呈相反趋。这意味着即使区域性平均温度变化一致，区域性强天气波动的变化趋势也会有所不同。

Influence of inhomogeneity on the estimation of mean and extreme temperature trends in Beijing and Shanghai

Inhomogeneities in the temperature series from Beijing and Shanghai are analyzed, using the detailed histories of both sets of observations. The major corrections for different periods range from -0.33 to 0.6?for Beijing and -0.33 to 0.3? for Shanghai. Annual mean and extreme temperature series are deduced from the daily observations and trends in the adjusted and unadjusted series are compared. The adjusted yearly mean temperatures show a warming trend of 0.5? / century since the turn of this century and an enhanced one of 2.0?/century since the 1960s. In contrast, the unadjusted data show a twice this value trend for Shanghai but little trend for Beijing at the long-term scale and overestimate the recent warming by 50%-130%. Beijing experienced a decrease of frequency of the extremes together with a cooling during the 1940s-1970s and an increase of frequency of extremes together with a warming since then. The trends of frequency of extremes at Shanghai were more or less opposite. It is implied that the regional trends of strong weather variations may be different even when the regional mean temperatures coherently change.