Changes Of Sunshine Duration And Simulation Of Solar Radiation In China's Mainland 1961-2016

As a kind of renewable energy,the development and utilization of solar energy is valued by many countries.As important factors to measure solar energy,the distribution and variation of sunshine duration and solar radiation have been paid much attention.This study based on the Chinese mainland 569 high quality meteorological site data,combined with 31 less lack of measurement and time series continuous solar radiation site data,used Manner-Kendall(M-K)trend test,M-K mutation analysis,Bernaola-Galvan(B-G)Segmentation Algorithm,and a variety of mutation testing methods,the spatial pattern and variation trend in sunshine hours and associated factors were studied during 1961-2016 in China's mainland,and the empirical model of optimal solar radiation simulation in China's mainland was explored and optimized.Finally,the variation trend of solar radiation in China's mainland was analyzed based on the optimized results.The results indicated that:(1)Annual sunshine duration in China's mainland decreased significantly at the rate of-40.7 h/10a.The decline was the most pronounced in the 1980s(3.46%).In addition,sunshine duration decline was the strongest in summer(-16.8 h/10a),followed by winter(-9.9 h/10a),autumn(-9.5 h/10a)and spring(-4.5 h/10a),respectively.The decrease of sunshine duration in the eastern region was significantly higher than that in the western region during 1961-2016,especially in North China.(2)Sunshine duration was positively correlated with wind speed(R=0.76);however,it was negatively correlated with mean temperature(R=-0.60)and precipitation(R=-0.41).Moreover,altitude and population density may affect the values and variations of annual sunshine duration over China's mainland.Air pollution has obvious weakening effect on sunshine hours.In the same region,the sunshine hours of days with serious pollution are shorter than those with less contamination,and the decline trend of sunshine duration in areas with serious pollution is more obvious than those with less contamination.Abrupt changes and accelerated decline in sunshine duration in the 1980s might have been caused by volcanic eruptions rather than the changes in meteorological elements.(3)The Angstrom-Bahel model(cubic model)is more suitable for the solar radiation simulation in China.According to the different trend transition time of sunshine hours and solar radiation,the simulation effect was better than that before the optimization.The solar radiation showed a decreasing trend in China's mainland from 1961 to 2016,which was divided into the "darkening" stage(-16.95 MJ/m·a)from 1961 to 1989 and the "brightening" stage(5.34 MJ/m·a)from 1990 to 2016.The biggest declines and increases occurred in the 1980s and 1990s,respectively.With the exception of autumn,each season shows the trend of"darkening" after "darkening ".During the "darkening" phase,the decline was the largest in winter,while in the "brightening" phase,the spring recovery trend was the most significant.There were significant differences in the solar radiation trend rates in two different stages,and solar radiation in four seasons has a tendency to decrease first and then increase(or decrease first and then stabilize).(4)For each climatic region,the solar radiation shows the highest decline rate in North China from 1961 to 2016(-8.22 MJ/m·a),followed by Central China(-5.67 MJ/m·a)and South China(-4.74 MJ/m·a).With the exception of North China,the solar radiation in each region showed a tendency of decreasing first and then increasing during 1961-2016,which was the same as that in the world.The above conclusions help us to understand the temporal and spatial distribution and changing trend of solar energy resources in China and the possible impact of climate change and human activities on it,which provides scientific support for the rational development and utilization of solar energy in China.