Temporal and Spatial Distribution in Solar Radiation and Sunshine in the "Three-River-Source" Region
三江源地区太阳辐射与日照时空分布特征

In this paper, data on sunshine duration was collated from 16 meteorological stations in the Three-River Source Region and the Yushu meteorological station from 1961-2008. Possible solar radiation distribution data were simulated by the improved Angstrom Model. Together, distribution characteristics of solar radiation, sunshine duration and latent influencing factors were analyzed. The results show that Maduo and Tongde, located in the northeast of the Three-river Source Region, had the highest level of sunshine duration: 2838.3 and 2812.4h respectively. The southern Jiuzhi, Banma, Dari and Gande areas had lower levels of sunshine duration; with the Jiuzhi area having the lowest duration in the Qinghai province of only 2349.3h. Possible sunshine duration in the Three-river Source Region was between 54% ~64%. The spatial distribution characteristics were similar to sunshine duration distribution. In the past 40 years, total sunshine change in most of the areas in the Three-river Source Region was not significant. Solar radiation was the most important factor determining regional climate, and it was between (5819.4~7579.2) MJ/m2 in the Three-river Source Region. The solar radiation value of 6819.9MJ/m2 simulated by a model in Zhiduo, was the highest value; whereas Jiuzhi had the lowest value at 5841.9MJ/m2. The annual average value of the whole region of 6751.08MJ/m2 was close to the average value for Qinghai province (6771.95MJ/m2). In the 1960s, total radiation, direct radiation and scatter radiation in the Three-river Source Region displayed an increasing trend, and the historical maximum of 6961.31MJ/m2 was observed in 1968. From 1970 to the late 1980s a decreasing trend was observed, and the minimum value of 5336.92MJ/m2 appeared in 1986. From 1992, total radiation began to rise and returned to 1960s levels in 2004. This change was similar to the global trend of first dimming after lighting.