秦岭南北夏季昼晴夜雨雨量时空变化及其影响因素

Spatio-Temporal Variation of Diel Composite Precipitation in Summer and Influencing Factors over the North and South of the Qinling Mountains,China

全球变暖趋势下,夏季昼夜复合高温频发,连续性降水减少,导致夏季降雨季节内昼夜配置关系发生改变。秦岭是中国重要的南北地理分界线。研究发现,近年来,秦岭南北35.0%的区域昼夜复合高温呈现显著增加趋势。然而,针对中国秦岭南北过渡带气候变化研究,过去以分析降水时空变化趋势为主,对全球变暖背景下昼夜降水组合的复杂性关注不足。本研究基于秦岭南北72个气象站点逐日降水数据,采用BG突变检测、趋势分析、投影寻踪回归模型等方法,对1970—2020年秦岭南北夏季昼晴夜雨雨量时空变化特征进行分析,探讨关中平原、秦岭南坡和汉江谷地昼晴夜雨雨量变化的影响因素。结果表明:(1)1970—2020年,秦岭南坡(3.08 mm/10a)和汉江谷地(3.10 mm/10a)夏季昼晴夜雨雨量显著增加,两者变化速率高于关中平原(1.14 mm/10a)。(2)1970—1982年,秦岭南北夏季昼晴夜雨雨量异常格局呈现“北多南少”,秦岭南坡、汉江谷地东段是昼晴夜雨偏少的集中分布区;1983—2020年,昼晴夜雨空间格局经历了“一致偏少”向“一致偏多”转变,秦岭南坡和汉江谷地昼晴夜雨雨量增加尤为明显。(3)秦岭南北夏季昼晴夜雨雨量主要受白天温度的影响。当夏季昼晴夜雨发生同期累积最高温增加10℃,昼晴夜雨雨量增加0.90 mm。本研究结论启示,夏季极端高温正在改变中国南北过渡带降雨昼夜形态,将增加区域水资源调配、粮食生产、生态服务等风险,上述结果可为区域综合风险防范体系构建提供理论依据与方法参考。

Under the trend of global warming,the frequent occurrences of summertime compound hot extremes lead to continuous precipitation reduction and have changed the diel precipitation pattern,even for whole summer rainfall season.The Qinling Mountains is an important geographical dividing line between the north and the south of China.It was reported that 35.0%of the areas in the north and south of the Qinling Mountains went through a significant increase in diel composite high temperature in recent years.Unfortunately,past study of climate changes in the transition zone between the north and south of the Qinling Mountains mainly concerned about the spatial-temporal variation of precipitation,less attentions to the implication of the diel composite precipitation under the background of global warming.Diel Composite Precipitation(DCP)refers to a pattern of precipitation to be observed on a 24-hour basis,particularly with emphasis on night rainfall ensuing from daytime serenity,which serves as a unique climatic resource,and a critical index of regional climate characteristics.In this study,it collected daily summer precipitation records in the period of 1970-2020 at 72 meteorological stations sparsely located at the north and south of the Qinling Mountains;the spatial-temporal variation of DCP was analyzed by BG mutation detection,trend analysis,projection pursuit regression model and other methods;then it discussed factors influencing DCP in the Guanzhong Plain,southern slope of the Qinling Mountains and the Hanjiang valley.The results showed that:(1)From 1970 to 2020,there was an increasing trends of DCP value in the southern slopes of the Qinling Mountains and the Hanjiang River valley,with an increase rates of 3.08 mm/10a and 3.10 mm/10a,respectively,which was twice higher than those in the Guanzhong Plain(1.14 mm/10a),and suggests that the variations of DCP responding to global warming in southern part of the Qinling were more sensitive as compared with those in the northern.(2)Between 1970 and 1982,the distribution pattern of abnormal DCP in the north and south of the Qinling could be characterized as more in the north and less in the south.To be specific,the southern slopes of the Qinling and the eastern part of the Hanjiang valley were areas with less DCP.Between 1983 and 2020,the spatial pattern of DCP anomalies shifted from less to more rainfall consistently;spatially,areas with high increase of DCP were in the southern slopes of the Qinling and Hanjiang valley.(3)Daytime temperature as main influencing factor contributed to the variations of DCP.In the case of cumulative daily maximum temperature with an up of 10℃,DCP increased 0.9 mm.Our findings reveal that hot extreme in summer has been changing the diel pattern of rainfall in the north-south transition zone of China.It possibly increases the risk of regional water resources allocation,food production,and ecological services,etc.It should be noted that above results shed new insights into diel variations in summer rainfall,which can offer implications for formulating integrated risk governance strategies in the north-south transitional zone of China.