武汉市气候变暖与极端天气事件变化的归因分析

Trends in Climate Extremes in Association with Climate Warming in Wuhan

根据武汉市1951—2007年间年平均、最高、最低气温与8类年极端天气日数的序列,计算分析其变化趋势及年平均气温与极端天气日数的相关性,引入格兰杰因果性检验法,探讨气候变暖与极端天气事件之间的因果关系。结果发现:(1)近57年来武汉市年平均最低气温增幅为0.45℃/10a,明显高于年平均最高气温0.19℃/10a的增幅,可见气候变暖主要是由夜间气温升高所致;(2)高温和闷热天气事件为增多趋势,其中闷热天气事件最明显,达到2.8 d/10a,而年雷暴、降雪、低温、大风、雾日则均为下降趋势,雷暴、雾和低温事件降幅明显,每10年减少3.0 d、4.0 d和2.1 d。大风和降雪事件,每10年减少1.8 d和1.5 d。暴雨事件波动幅度较小。(3)年平均气温与当年及超前、滞后1～2年的极端天气事件具有高相关性;(4)格兰杰因果性检验结果发现,气候变暖是闷热天气增多和降雪事件减少的原因,同时亦是大风和低温减少的结果。这种因果关系的存在对极端天气事件预测和预估有重要的价值。

Based on the data series of the annual mean,highest,and lowest temperatures and annual day numbers for 8 kinds of extreme weather events from 1951 to 2007 in Wuhan City,the trend and the relationship between annual mean temperatures and the day numbers with extreme weather are analyzed.By introducing the Granger causality detection algorithm,the relationship between climatic warming and extreme weather events is studied.The results show that：（1） the increase rate of annual mean lowest temperature in Wuhan in recent 57 years is 0.45℃/10a.which is much higher than that of the annual mean highest temperature of 0.19℃/10a.It indicates that the climatic warming is mainly caused by nighttime temperature increasing.（2） The frequency of high temperature and muggy weather events increased with year.The increasing rate of muggy weather is 2.8 d/10a and more evident than high temperature.The frequency of thunderstorm,snow,low temperature,gale,and fog decreased evidently with year.The decrease rates of thunderstorm,fog and low temperature are much larger and are 3.0,4.0 and 2.1 d/10a respectively. The decrease rates of gale and snow events are 1.8 and 1.5 d/10a.The fluctuation of rainstorm events is small.（3） The annual mean temperature is highly correlated with the extreme weather events at time periods 0 years（concurrent） or±（1-2） years（leading or leg）.（4） The Granger causality detection results show that the climatic warming is the causes for the muggy weather increasing,snow event decreasing, and the gale and low temperature decreasing.The existence of causality is very valuable for the forecast of extreme weather events.