| Ultraviolet(UV) radiation of the sun radiation plays an important role on the environment we live in, appropriate dose of UV radiation is good for our body, but excessive dose of UV not only damages human health, but also has bad influences on other plants and animals. However, only few research institutions observation sites have UV radiation observation, while routine meteorological observatories don’t have. Therefore, we have to do researches of calculating the UV that reaches the ground, surely the study has important significance for guiding people to protect from UV, and practical significance in urban planning and construction, energy use, environmental protection.With 39 sites daily UV observation data during 2010～2012 provided by the Chinese Ecosystem Research Network (CERN), we calculate and analysis the time-space distribution characteristics of UV on mainland China; based on the atmosphere solar radiation transmission theory, and combine with the practical situation of our country’s ground meteorological observatory at present, we establish UV calculation models considering various factors, our models are of high precision and wide applicability.The main results are following as:(1) By analyzing the UV time-space distribution characteristics over mainland China with UV daily observation data of 39 CERN sites, it shows that:For space distribution, basically take the UV value of 20 W/m2 contour line as dividing line; in the west of contour line, UV value is high over the Tibet plateau, Eastern Xinjiang, Gansu, and Inner Mongolia region, and Tibet plateau and Inner Mongolia’s Xilingol are highest value center, while southwest of Xinjiang is much lower; in the east of contour line, UV value is generally lower than west, North China and from South Shanxi, East Sichuan to Chongqing, Guizhou, Hunan, Hubei are two lower value area, and Chongqing area is the lowest. In the east of contour line, there are more cloud, due to rapid urbanization and large-scale industrialization, and the AOD is larger, coupled with lower altitude and more ozone value, lead to lower UV. While west of the contour line, there have more sunny days, and less cloud, higher altitude leads to less ozone and cleaner air, with smaller AOD, so the UV radiation is higher; Southwestern Xinjiang region is in the west of the Taklamakan desert, and there are quite frequent sand storms and larger AOD, lead to lower UV. In addition, with the UV radiation data of Beijing urban and suburbs, Taihu site and Changshu site, it shows that suburb’s UV radiation is higher than urban’s UV in generally. For the time distribution, UV radiation is low in winter half year, and high in summer half year. July and Aug. have the highest UV radiation, while Dec. and Jan. have the lowest. In a day, UV is highest at 12 O’ clock.(2)With AERONET Beijing station daily observation data in 2011 and CREN UV radiation data of the same period, based on the atmospheric radiation transmission theory, we established the Beijing station UV radiation calculation model, and corrected the model with method of stepwise regression, and verified the model with 2005～2010 relevant data. When fitting the model, the correlation coefficient is 0.99, the relative error is 5.13%; while evaluation, the correlation coefficient is 0.97, the relative error is 8.14%. Compare the model with SMARTS model, the result shows that, the correlation coefficient is 0.08 higher, and the relative error is 8% lower. Meanwhile, separate calculation and correction of the Rayleigh scattering formula, nitrogen dioxide absorption formula, ozone absorption formula, and aerosol absorption formula shows that molecular scattering, ozone absorption and aerosols absorption is the most important factors that affect UV radiation. While molecular scattering contribution is the largest, and aerosol particles attenuation of UV radiation is the most sensitive factor. As seen above, UV radiation calculation model established in this paper is of high accuracy and stable.(3) Because the AERONET sites in China are not enough, and most of the meteorological observation sites don’t have aerosols data, so we use the ground meteorological data to modify the above model. The specific method is as follows: calculate the UV radiation of target site with its air pressure and column total ozone data first, and then use ground meteorological data of the site within 30 km for correction. Calculation models of Beijing station and the other 31 meteorological observation stations related to 19 CERN sites are established based on this method, all the models are on list of model libraries. With the data of 2010 and 2011, the model fitting correlation coefficient is 0.79, the relative error is 25.7%; while evaluating the model with the data of 2012, correlation coefficient is 0.74, the relative error is 28.9%. Verification results are similar with fitting, it shows that the method is good and stable.(4) Though most of the meteorological observatories have no UV radiation data, but more than 100 sites have solar radiation observation projects, so we take solar radiation as a correction factor to join the calculation model, and establish UV radiation calculation model of Beijing site. When fit the model, the correlation coefficient is 0.98, the relative error is 7.3%; while evaluating the model, the correlation coefficient is 0.98, the relative error is 7.8%. After taking in solar radiation, the precision of the calculation model is higher than without. Since many sites have solar radiation data and few sites have UV radiation data, so this UV calculation model explores a feasible and high precision of calculation method to those sites.(5) Because some observation sites don’t have any radiation data, therefore, we also establish a UV radiation calculation model for these sites. The specific method is:for one target site, select some reference sites within 450 Km that already have calculation models established above, with these reference sites calculation model fitting coefficient through the IDW(Inverse Distance Weighting) algorithm, calculates the target site’s fitting coefficient, finally it establish UV radiation calculation model of the target site. Take Jiangxi Qianyanzhou site as the target site, we establish its UV radiation calculation model. The results show that:the correlation coefficient is 0.83, and the relative error is 25.8%. (All the correlation coefficients above are accepted at the 5% confidence level)All in all, this paper discusses UV radiation calculation models under different conditions, and provides the reference for the calculation and forecast of UV radiation for all meteorological stations. |
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