1970—2020年秦岭南北夏季昼晴夜雨强度变化趋势及其影响因素

Changing Trends and Influencing Factors of the Intensity of Summer DaySunny and Night Rainfall in the North and SouthofQinling Mountains from 1970 to 2020

[目的]在陕西3大地理单元中,秦巴山区土壤侵蚀强度仅次于黄土高原。明晰秦岭南北夏季昼晴夜雨强度与气候变暖的响应关系,对区域土壤侵蚀防治具有重要的意义。[方法]基于1970—2020年逐日降水数据,辅以BG分割法、经验正交函数和Lasso回归等方法,对秦岭南北地区夏季昼晴夜雨强度时空变化特征及其影响因素进行分析。[结果]1970—2020年,秦岭南北夏季昼晴夜雨强度呈现显著增加趋势。空间上,秦岭南北夏季昼晴夜雨强度主导模态为全区一致增强。其中,1000 m以下的谷地和平原区,是夏季昼晴夜雨强度变化的敏感区。在影响因素上,秦岭南坡、汉江谷地夏季昼晴夜雨强度变化与气象因子相关性高于关中平原。其中,秦岭南坡夏季昼晴夜雨强度主导气象因子为日照时间,而汉江谷地则受日照时间和平均风速的共同影响。[结论]2003年后秦岭南北夏季昼晴夜雨强度存在突变增强。以白天高温、夜间强降水为侵蚀形态的降水类型,将成为秦岭南北水土保持防治的重点。

[Objective]In Shaanxi Province,the intensity of soil erosion in the Qinling-Daba Mountains is next only to that of the Loess Plateau.The study of response relationship between the intensity of summer day sunny and night rainfall(DSNR)and climate warming is of great importance for the control of soil erosion in China’s north-south transition zone.[Methods]Based on daily precipitation data in summer(June to August)of 72 meteorological stations,assisted by B-G segmentation,empirical orthogonal function(EOF)method and Lasso regression model,we analyzed the spatiotemporal variation and influencing factors of the intensity of DSNR at summertime in the north and south of Qinling mountains during the period 1970—2020.[Results]From 1970 to 2020,the intensity of DSNR in summer exhibited a significantly increasing trend,which was more obvious in Hanjiang River Valley[0.30 mm/(d·10 a)].Spatially,the leading mode of the intensity of summer DSNR can be characterized by“consistent enhancement across the whole region,with a higher degree of anomalies in the valleys than in the mountains”.It indicated that valley-plain areas below 1000 m were sensitive to variations in the intensity of DSNR at summertime.In terms of influencing factors,the correlation between evolution in the intensity of DSNR at summertime and meteorological factors in the Hanjiang River Valley and southern slopes of Qinling Mountains was higher than that in Guanzhong Plain.In addition,cumulative duration of sunshine was the leading climatic factor driving the changes of summer DSNR intensity in the southern slopes of Qinling Mountains,while the variations of summer DSNR intensity in the Hanjiang River Valley was jointly influenced by cumulative duration of sunshine and average wind speed.[Conclusion]The year 2003 was a mutation year after which the intensity of DSNR at summertime began to be greater in the north and south of Qinling mountains.It informs us that,in the north and south of Qinling mountains,we should put the focus of soil and water conservation on the precipitation type with high temperature in the day and heavy precipitation at night.