关键词: 秦岭南北, 日照时数, 时空变化, 突变点, 影响因素

Abstract: In recent years， along with global warming，increasing population density， quickening urbanization progress，climate elements such as corresponding temperature，sunshine hours have taken distinct changes. Scholars in China have done abundant study on the characteristics of sunshine hour changes and its response to climate changes. Many meaningful conclusions have been drawn. Sunshine hours are the most direct representation of radiation quantum. The change of sunshine hours affects the growth of plant， animal and the anthropogenic activity. The Qinling Mountains is the most important climatic separatrix of north and south of China. In this paper， the series of annual and seasonal sunshine hours in the northern and southern regions of the Qinling and Dabashan Mountains were developed using the sunshine hours data from 47 meteorological stations in the northern and southern regions of the Qin and Dabashan Mountains during the period of 1960-2011. The distribution and temporal and spatial variation characteristics of sunshine hours as well as the meteorological elements which influenced sunshine hours were analyzed using the methods of Spline interpolation method， climate trend rate， Pettitt abrupt change point detection， correlation analysis and others. The results are as follows：（1）Yearly averaged sunshine hours are 1 838.7 h，with the spatial distribution pattern of high value in northeast region and low in southwest. Four seasons' sunshine hours present the same distribution characteristics like the annual sunshine hours，with summer’s sunshine hours ＞ spring’s＞ autumn’s ＞winter’s，which is in climatology’s linear law. （2）According to the percentages of stations with sunshine hours decreasing trend in recent 52 years，whose orders are as follows：Ba-Wu valley’s stations＞Han River basin’s＞Qinling Mountains northern region’s＞ Qinling Mountains southern slope’s. The decreasing trend in southern region was more obvious than that in northern region of Qinling Mountains. 94% and 98% of stations were in decrease of sunshine hours in winter and summer，respectively.  However，characteristics of change in sunshine hours and its spatial distribution were without an obvious regularity. The downward trend in winter sunshine hours is probably due to dust-floating increasing in the atmosphere because a large amount of coal is being consumed by human being in winter. （3）The abrupt change in annual，spring and summer sunshine hours happened between 1979 and 1981 and there were no obvious abrupt change points in autumn or winter，which may be due to the urbanization development and cloud cover increasing. （4）Wind speed and maximum temperature are positively correlated with sunshine hours，while precipitation and relative humidity are passively correlated with sunshine hours. There was no a clear relationship between minimum or mean temperature and sunshine hours．

Key words: the northern and southern regions of the Qinling and Dabashan Mountains, sunshine hours, spatio- temporal variations, abrupt change point, influential factor