Changing Trends and Influencing Factors of the Intensity of Summer Day Sunny and Night Rainfall in the North and Southof Qinling Mountains from 1970 to 2020

Abstract

[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 1 000 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.

Keywords

• climate change
• day sunny and night rainfall
• spatiotemporal analysis
• lasso regression
• north and south of qinling mountains