气温突变下内蒙古大兴安岭林区旱涝演变

Occurrence of Drought and Flooding Affected by Abrupt Temperature Change in Daxing'anling Forest in Inner Mongolia

【目的】探明内蒙古大兴安岭林区气候变化趋势及旱涝演变特征。【方法】基于内蒙古大兴安岭林区11个气象站1971—2015年年平均气温和月降水连续观测数据,利用一元线性回归、Mann-Kendall法以及标准化降水指数(SPI)方法进行了研究。【结果】(1)内蒙古大兴安岭林区年降水量在近1971—2015年来整体呈波动上升趋势,年际变化倾斜率为8.86 mm/10 a,但未通过显著性检验;年平均气温也呈上升趋势,并且通过0.001的显著性水平检验,年际变化率为0.4℃/10 a;(2)林区年平均气温在1987年发生增温突变,气温突变以后年降水量倾向率明显减小;(3)1971—2015年来林区旱涝频繁发生,20世纪70年代与21世纪00年代SPI12多小于0,这2个时期干旱发生较为频繁,而20世纪80年代至90年代以及21世纪10年代降水较多,这2个时期相对湿润,旱灾发生频率较低。【结论】1987年增温突变以后,林区旱涝事件发生更加频繁,并呈向极端干旱和极端湿润的方向发展;年时间尺度的SPI反映林区降水变化情况比较理想。

【Objective】This paper aims to analyze the change in occurrence of drought and flooding in Daxing＇anling forest in Inner Mongolia due to climate change and to provide baseline for studying the occurrence of drought and flooding, as well as ecological restoration and disaster prevention.【Method】Based on the measured average daily temperature and precipitation from 1971 to 2015 in this region, we analyzed their relationship using linear regression, the Mann-Kendall test（Mann-Kendall） method and the standardized precipitation index（SPI）.【Result】（1）The annual precipitation showed an rising trend over the past 45 years, with an increasing rate of 8.9 mm per decade although the increase was insignificant（failed the significant test）. The annual mean temperature also showed a rising trend at significant level（p〈0.001） with a rising rate of 0.4 ℃ per decade.（2） The annual mean temperature in the forest area endured an sudden change in 1988, followed by a decrease in annual precipitation.（3） In the past 45 years, forest drought occurred frequently and in the 1970 s and early 2000 s, the value of SPI12 was less than 0. In the 1980 s and 1990 s and 2010 s, however, there was a rise in precipitation, reducing the drought frequency.【Conclusion】Following the abrupt change in temperature in 1987, the forest areas saw an increase in both drought and waterlogging, becoming either extremely dry or wet. The SPI at annual scale reflects the change in precipitation in the region.