利用格兰杰因果检验法分析重庆极端气温事件及其与平均气温和降水量变化的关系

Extreme Temperature Events in Chongqing and Their Relation with the Mean Temperature and Precipitation Change Based on Granger Causality Test

根据重庆1951-2010年逐日最高气温、最低气温、平均气温和降水量数据,用百分位阈值法和固定阈值法定义了重庆极端气温事件,统计分析结果显示两种方法定义的极端事件的变化趋势大体一致,20世纪80-90年代为极端高温事件少发期,且80年代极端高温事件强度相对较低,其它时期极端高温事件相对多发且强度相对较大;极端低温事件及其强度以80年代中后期为分界点,之前多发且强度较大,之后少发且强度较小。运用格兰杰因果检验法分析极端气温事件与平均气温和降水量变化的关系,结果表明,高温日数的增多和低温日数的减少,以及低温强度的减弱,是平均气温上升的格兰杰原因,高温事件强度和降水量变化存在统计意义上的因果关系。格兰杰因果检验为判断和分析事件间的相互关系提供了一种新的统计方法,具有借鉴意义。

The threshold of extreme temperature events was defined by percentile and agrometeorological service, according to the series data of daily temperature and precipitation in Chongqing from 1951 to 2010. The statistical results showed that the trends of the extreme temperature events defined by two methods were featured with similarity. The trends appeared that the extreme maximum temperature events in 1980s -1990s were relatively few and the strength was relatively weak in 1980s, which was opposite to that in other periods. The Granger Causality Test was used to analyze the relation between the extreme temperature events and the change of mean temperature and precipitation, and the results showed that the causes of the rise of annual average temperature were the rise of frequency of extreme maximum temperature events and the fall of frequency of extreme minimum temperature events, and also the weakening of the strength of the extreme minimum temperature events. It was also showed that the strength of the maximum temperature events was the cause of precipitation change in statistical sense. The Granger Causality Test is a new statistical method to analyze the relationship of different events.