Abstract
Sunshine hours is one of the most important factors affecting climate and environment. Trends of temporal and spatial patterns in sunshine hours and associated climatic factors over southwestern China are evaluated for the period 1961–2008 based on data from 110 meteorological stations. The results show that southwestern China is experiencing statistically decreasing sunshine hours with rate of 31.9h/10a during 1961–2008, and the statistically significant decrease of sunshine hours mainly occurred in lower altitude regions, especially in Sichuan basin and Guizhou plateau. It showed the closely temporal and spatial correlation between wind speed and sunshine hours, and the larger decreasing trend displayed declining trend in nonwindy days than that in windy days. This is strongly suggestive of the fact that stronger winds lead to longer sunshine hours, further validating that wind speed directly and strongly influences sunshine hours in southwestern China. The relative humidity also has a great influence on sunshine hours reflected by the significant correlation and the similar trend between the two variables. Sunshine hours also has a high correlation with precipitation and surface downwards solar radiation flux, whereas the effect from urbanization on regional-scales trend was inconspicuous. The increased total cloud cover and cloud water content from 1960s to 1970s, and the decreased relative humidity and increased surface downwards solar radiation flux between 1980s and 1990s have also influenced the variation of sunshine hours. In addition, the clear local influence of topography can be reflected by the decreasing magnitudes increased from summit to flat stations.
Published Version
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