长江与黄河流域复合高温干旱事件时空演变特征

Spatiotemporal evolution characteristics in compound hot-dry events in Yangtze River and Yellow River basins

利用1961—2014年月降水与日最高气温数据,定义了3d/90%型和5d/90%型两类复合高温干旱事件,比较分析了长江流域和黄河流域夏季复合高温干旱事件的分布特征与时空变化规律,量化了复合高温干旱事件与单独热浪事件的温度差异。研究结果表明:复合高温干旱事件在长江流域中下游地区发生频率较高,在黄河流域空间差异不大;两流域复合高温干旱事件频率均呈增加趋势,长江流域3 d/90%型和5 d/90%型复合高温干旱事件日数增加趋势分别为每10 a 0.19 d和0.14 d,黄河流域的增加趋势分别为每10 a 0.29 d和0.096 d;长江流域复合高温干旱日数在西北部与南部地区增加较多,下游东北部地区有所减少,黄河流域在中部和西部增加较多;两流域1988—2014年复合高温干旱事件影响范围总体上比1961—1987年增加,黄河流域影响范围占比大于长江流域;相比于单独热浪事件,复合高温干旱事件的平均温度更高,长江流域和黄河流域3 d/90%(5 d/90%)型复合高温干旱事件与单独热浪事件平均气温差值分别为0.65℃和0.64℃(0.54℃和1.21℃)。

Based on the data of monthly precipitation and daily maximum temperature from 1961 to 2014,the distribution characteristics and spatio-temporal changes in compound hot-dry events in the Yangtze River and Yellow River basins were compared and analyzed based on two types of compound hot-dry events(3d/90%type and 5d/90%type).The temperature difference between compound hot-dry events and single heatwave events was quantified.The results showed that the frequency of compound hot-dry events was relatively high in the middle and lower reaches of the Yangtze River Basin,and the spatial difference was not significant in the Yellow River Basin.The frequency of compound hot-dry events in the two basins showed an increasing trend.The number of days of 3d/90%and 5d/90%type compound hot-dry events in the Yangtze River Basin increased by 0.19d and 0.14d per 10a,respectively,and the increase of the Yellow River basin was 0.29d and 0.096d per 10a,respectively.The number of compound hot-dry days in the Yangtze River Basin increased more in the northwest and southern regions,while the frequency in the northeast region of the lower reaches decreased.The number of compound hot-dry days in the Yellow River Basin increased more in the central and western regions.The area impacted by compound hot-dry events in the two basins from 1988 to 2014 was generally higher than that from 1961 to 1987,and the impacted area of the Yellow River Basin was larger than that of the Yangtze River Basin.Compared with the single heatwave events,the average temperature of the compound hot-dry events was higher.The average temperature difference between the 3d/90%(5d/90%)type compound hot-dry events and single heatwavce events in the Yangtze River Basin and the Yellow River Basin is 0.65℃and 0.64℃(0.54℃and 1.21℃),respectively.