| Solar radiation is the primary energy source of various physical processes in the natural environment, and is basic force of driving weather and climate format and evolute. Solar radiation is main source of energy of the terrestrial ecosystems. When solar radiation goes through the atmosphere, due to absorption, reflection and scattering of clouds, water vapor and atmospheric gases such as CO2 ozone and aerosol particles, it reduces. The solar energy resources of China are abundant. The total solar radiation exposure yearly around China is 3350-8370MJ/m2. Solar energy resources in most areas of China are better than ones of other countries such as Europe and Japan where solar energy is highly developed. Solar energy has great potential for development. This thesis is based on long-term (1961～2009) total solar radiation, direct radiation and diffuse radiation, and observations of meteorological elements. It uses linear trend, wavelet Analysis and Mann-Kendall(M-K) statistical test methods to analyze China's long-term variation of surface solar radiation. It is also based on short-term forecasting model based on WRF Experimental Studies. The results show that:(1)Regional long-term trend of global solar radiation in China:The global radiation and another meteorological elements data (1961～2009) from 58 meteorological stations is applied to analyze the global radiation characteristics and its relationship with another elements by the liner-trend estimation, wavelet analysis and M-K test. The results show that: Between of these 58 weather stations, the passages of significance test of 34 stations are at 95% confidence level. Meanwhile, among these 34 stations, the global radiation trend is ascent, but that is different from different area. The trend of the decadal deviation percentage:the main trend in 1960s is ascent, but gradually it dropped in the 70s, and it decreased significantly after 80s.After 90s, a little site are increase slightly. The trends of the cumulative variance have four types, such as up-down, up-down-a little elevation, up-down-no significant increase. For inner year change, there is the most obvious decline in winter, while a little decreases in spring, summer and autumn. The major cycles of global radiation are 6～9a,10～13a,29～33a. The sudden change periods are almost in the 70s. The reasons which lead to more changes are complex. According to the solar radiation with the relevant elements by statistical methods, the respectively relationship between the annual sunshine percentages, annual average wind speed, blowing sand and the average number of days low cloud cover with the global radiation are closer. In addition, the effect of climate change by human-induced is also important for such region distribution. Especially, the percentage of sunshine and mean annual wind speed was positively correlated with the annual total solar radiation. But the annual average temperature was negatively correlated with solar radiation, which may cause the temperature increase in the greenhouse. Some elements locally, such as blowing dust days and number of days should be negatively correlated in practical, but it is positively correlated by statistic. The impact mechanism is not clear, and needs further study.(2)The trend of direct and diffuse radiation in China over recent 50 years:In this paper, we used the direct and diffuse solar radiation data during 1961-2009 from 14 stations and during 1961-1991 from 49 stations in China. The present study based on the method of linear regression (taken time as an independent variable), wavelet analysis and Mann-Kendall statistical test. The characteristics of the direct and diffusion radiation are analyzed from different angles including that of decadal variation, long-term seasonal change, inter-decadal anomalies, cycle and abrupt change. The results showed:①The spatial and temporal distribution of the climatic trend for the direct and diffuse radiation was revealed by using the normalized climatic tendency coefficient. At the same time, these results are comparable.②The direct solar and diffuse radiation in China showed decrease trend, but there are many difference in the regions, inter-annual and seasonal trend of them.③Based on the characteristics of the geographical distribution on observation stations, according to the climate zone, it is classified with the percentage of sites by statistical method. A certain area and Local differences were exhibited clearly in the long-term changes of the radiation.④Using wavelet and MK test method, the statistical results show that the radiation in different regions with different period and abrupt change.⑤The long-term trends of the direct and diffuse radiation in most part of the provincial cities were decrease which was more obvious than in other cities. According to some study, such climatic phenomenon may be caused by environmental factor changes of urbanization relating to the development of different cities.(3)The influence of urbanization on solar radiation in China:The urban population, solar radiation and related meteorological observation data in 13 major cities was analyzed by the liner-trend estimation method. The results show that:In recent decades, due to urbanization and increasing population, the urban environment change caused by human activities had affected the long-term variations of surface solar radiation.①the urban population and the tendency coefficient of the global radiation was significant. The global radiation coefficient was decrease with the city size;②Ther are some relationship between the population data and the ground global radiation among 13 cities. Such relationship could be simulation by polynomial curve. Most of them the city could through the test of significance;③among the 13 cities, the changes of solar radiation and has a certain correlation with the urban population increasing, and the related coefficient of some city could be through the significance test (α= 0.05).The trend of the ground solar radiation due to the urban environmental conditions vary. Among them, some city show increasing trend, such as Lhasa, Guangzhou, and so on, showed an increasing trend in the city of the Golmud and Beijing, and so on. Direct solar radiation on the ground tended to decrease in the city of Zhengzhou, Urumqi, and so on, showed an increasing trend in the city of Lhasa, Lanzhou, and so on. The Ground diffuse solar radiation on a decreasing trend in the city of Golmud, and Lanzhou, and so on, showed an increasing trend in the city of Zhengzhou, Shanghai, and so on. The ratio of diffuse and direct radiation tended to decrease in the city of Golmud and Lanzhou, showed an increasing trend in the city of Zhengzhou, Chengdu, and so on. The ratio of direct and global radiation tended to decrease in the city of Zhengzhou, Shenyang, and so on, showed an increasing trend in the city of Golmud, Lhasa and Lanzhou, and so on. The ratio of diffuse and global radiation tended to decrease in the city of Golmud and Lanzhou,, showed an increasing trend in the city of Zhengzhou, Shenyang, and so on.(4)Review on methods of solar forecasting:reference to a large number of domestic and foreign literature about solar energy prediction, it was summarized and reviewed on the principle and mechanism of the solar energy prediction, the method for solar forecasting and its application. Solar forecast, including forecasts of solar radiation and photovoltaic solar power, is important for photovoltaic power generation system in network operation. Among them, the solar radiation prediction methods are involve the traditional statistics, neural networks, satellite remote sensing and numerical simulation methods; photovoltaic power generation forecast method is mainly statistical. Based on the application of photovoltaic power generation needs, the different advantages and disadvantages of some forecasting methods will be analyzed. At the same time, a lot of problems for further solar forecasting techniques research with the development of domestic will be proposed in this paper. In term of some case about practical solar energy, the main method is that satellite data, model predictions, meteorological observations data combine with statistics extrapolation methods and neural network, but numerical weather model is still the forecast difficult currently. Therefore, in the future, as for better effect of solar energy forecast, the solar forecasting technology includes model results, satellite remote sensing data, ground observations, and so on. (5)The global solar radiation short-term forecasting based on WRF model:The prediction test is on Turpan weather station for a trial of the next 60 hours in April 2010.The forecast results could be divided into two sections of 24 and 48 hours to statistical analysis.The results show that:The forecasting results are basically consistent with the actual observations data. The global radiation in cloudy could be forecasted. In addition, it could describe the global radiation during weather condition transformation. The hourly global radiation forecasts in two periods during the daytime have good correlation with the observed values, and it was adopted by the significant testα= 0.01. The correlation between hourly relative error during the daytime and prediction values are also good, by the significance testα= 0.01. For the average relative error of the prediction results and measured values, two-thirds days of were less than 25%. For the mean hourly relative error in daytime, the relative error at noon was least(less than 5%); the relative error during 9:00-14:00 was less than 20%, but the relative error sooner or later was up to 50% and above.
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