1960-2017年黄河流域极端气温的季节变化特征及其与ENSO的相关性分析

Characteristics of Seasonal Changes in Extreme Temperature and Their Relativity with ENSO in the Yellow River Basin from 1960 to 2017

为了研究黄河流域多变的气候变化特征,基于黄河流域66个气象站点1960—2017年逐日平均气温资料,应用线性趋势、Mann-Kendall法对该区域极端气温的季节变化特征进行了分析。结果表明:黄河流域极端高温天气的日数在各个季节均呈现出显著增多的趋势,而极端低温天气的日数在四季却呈现出显著减少的趋势。在整个研究时段内,黄河流域极端气温的季节变化(极端高温天气日数增多和极端低温天气日数减少)较为显著,且升温趋势主要发生在1991—2017年。从空间尺度来看,春、夏和秋季黄河流域极端高温天气日数在大多数地区呈现出增加趋势,仅有个别站点呈现出减少趋势;而冬季极端高温天气日数在整个研究区均呈现出增加趋势,最显著的区域集中在黄河中游大部分地区。而各季节极端低温天气在大多数站点呈现出减少趋势,仅有少数站点呈现增加趋势。总之,在整个研究时段内,黄河流域平均气温的升温趋势(极端高温天气增多和极端低温天气减少)较为显著,且升温趋势主要发生在1991—2017年。黄河流域极端高温天气日数在春、夏、秋和冬季发生突变的时间点分别为2000年、2001年、1994年、1995年,极端低温天气在春、夏、秋、冬季发生突变的时间点分别为2006年、2015年、1988年、1990年;除夏季外,其他季节极端高温天气与极端低温天气的突变的时间点较为接近,秋、冬季极端气温天气对全球气候变暖的响应均比春、夏季要早。此外,交叉小波分析表明黄河流域极端高温与低温和厄尔尼诺—南方涛动(ENSO)指数存在多尺度的显著相关性。

To have a better view of climate changes and trends,the primary objectives are to investigate the characteristics of seasonal changes in extreme temperature in Yellow River basin.Based on the daily mean temperature data of 66 meteorological stations in the Yellow River Basin during the period 1960—2017 and using the methods of climate tendency rate,Mann-Kendall and cross-wavelet and wavelet coherence techniques,the characteristics of seasonal changes in extreme temperatures and the relationship between the extreme temperature and the ENSO were analyzed.The results indicate that extreme high temperature days in each season presented the significantly rising trend,especially increased with larger scales after the middle of the 1990 s,but those was contrary to extreme low temperature days,which decreased with larger scales after the middle of 1990 s in spring and summer;the mutation of extreme high temperature days in spring,summer,autumn,and winter increased in 2000,2001,1994 and 1995,respectively,but those of extreme low temperature days decreased in 2006,2015,1988 and 1990,respectively;The response of extreme temperature days to global warming was earlier in autumn and winter than that in spring and summer,which indicated that the significant change of extreme temperature days took place in winter firstly;The response of extreme temperature days to global warming was earlier in autumn and winter than those in spring and summer;the change of extreme temperature days will exert some effect on the Yellow River Basin.Furthermore,the continuous wavelets transform analysis presented significant periodic variations with periods of 2~4 years,4~6 years in the extreme temperature.The increase of extreme high temperature days will add the pressure of preventing fire of forest and grasslands in the upper reaches of the Yellow River Basin.The decrease of extreme low temperature days will reduce the occurrence frequency of freeze damage,but it will be a potential threat to protection of ecology environment and agriculture production.