北京气候变暖与主要极端气温指数的归因分析

在对资料进行均一化处理的基础上,分析了北京1960—2008年气候变暖及主要极端气温指数的统计特征,并应用格兰杰检验法对其进行归因分析。结果表明:(1)近49 a来北京年平均气温增速约为0.39℃/(10 a),气候增暖具有明显的非对称性。(2)霜冻指数和气温年较差呈下降趋势,降幅为3.9 d/(10 a)和0.8℃/(10 a)。生长季指数、暖夜指数及热浪指数则呈上升趋势,增幅平均达3.0 d/(10 a)、0.75%/(10 a)和1.5 d/(10 a)。(3)北京年平均气温是霜冻指数、生长季指数及暖夜指数发生变化的格兰杰原因。虽然年平均气温与热浪指数在不同滞后期均具强相关性,但是检验表明它们之间并无显著的因果关系,很可能是由于某种原因导致的一种统计上的伪相关现象。

AN ATTRIBUTION ANALYSIS BETWEEN THE CLIMATE WARMING AND EXTREME TEMPERATURE INDICES IN BEIJING IN THE PAST 49 YEARS

Using the homogenized temperature data series during 1960—2008,the characteristics of climate warming and variation of extreme temperature indices in Beijing are analyzed.By introducing the Granger causality detection algorithm,the relationship between climate warming and extreme temperature indices is studied.The results have the following indication.(1) The increase rate of annual mean temperature is 0.39 ℃/(10 a),and the mean maximum and minimum temperatures change asymmetrically.(2) The decreasing rates of frost days(FD) and extreme temperature range(ETR) are 3.9 d/(10 a) and 0.8 ℃/(10 a),respecitively.The frequency of growing season length(GSL),warm nights(WN90) and heat wave duration index(HWDI) increase evidently with year,with their increasing rates at 3.0 d/(10 a),0.75%/(10 a) and 1.5 d/(10 a),respecitively.(3) The Granger causality detection results show that the climate warming is the cause of the variation of FD,GSL and WN90.The existence of causality is very valuable for the forecast of extreme temperature events.