Establishing A Solar Radiation Measurement Network In Chinese Ecosystem Research Network And Study On The Distribution Characteristics Of Ultraviolet And Photosynthetically Radiation In China

Establishing a solar radiation measurement network in Chinese ecosystem research network (CERN) is essential for assessing the theoretical treatments of radiative transfer in the atmosphere, verifying the model computations, and providing the fundamental data for weather forecasting, climate change diagnosis, and establishing the sustainable development policy for china. The radiation measurement network in CERN is not only useful to climate research but also useful to other researches such as ecology and energy resource. The measurement results are the basic data for revealing the formation of climate, predicting the tendency of climate change, and programming the development policy of agricultural and forest, especially for exploiting clean renewable energy resource and diplomatic negotiating of environment. A solar radiation measurement network is established in China typical terrestrial ecosystem with scientific management, united standard measurement procedures, standard calibration procedures, and standard criterion for the data quality. The distribution characteristics of Ultraviolet radiation and Photosynthetically active radiation are analyzed with these measurement data. The main content and results of this work are presented as follows. The absolute cavity pyrheliometer (PMO6-CC), sun tracker (2AP) and alternate method are used to establish pyranometers calibration system in the ground-base radiation measurement network in Chinese ecosystem research network. The accuracy of the calibrated pyranometer is within 3%. This accuracy is up to the WMO criterion of the solar radiation study. The alternate method used to calibrate pyranometers for network measurements can reduce the uncertainty of the measurement results. Standard radiative lamp and spectroradiometer (USB2000-UV-VIS and a CC3-DA Direct-attach Cosine Corrector) are used to establish broadband UV radiometer and quantum sensor Li-Cro 190SZ calibration system. The accuracy of the calibrated broadband UV radiometer is within 5% that meets the WMO criterion of UV radiation study. The accuracy of the calibrated quantum sensor Li-Cro 190SZ is within 5%. This accuracy is up to the WMO criterion of photosynthetically active radiation study. This reliable, accurate and inexpensive calibrate system can be applied to radiation network measurement. In Beijing city, there is only a little difference in Ultraviolet radiation (UVR) between 320 m and 140 m in high visibility day. But a significant difference between 140 m and 8m always exists. The variation of the diurnal attenuation ratio of UVR follows a hyperbolic law. Large attenuation appears in the morning and at dusk, and smaller attenuation at noon. In the vertical, the variation of the UVR attenuation in the lower layer is higher than that in the upper layer. This variation rule of UVR is caused by the vertical distribution of aerosol concentration. An intensive experiment was carried out in dust storm in Beijing from March 27 to 29,2004. Based on the measurement, the characteristics of solar radiation, the variation of atmospheric aerosol concentration (PM10 and PM2.5), the variation characteristics of meteorological factors, and the relations between aerosol and solar radiation in the dust storm period were analyzed. The results showed that the ratio of ultraviolet radiation to global radiation was different from that of photosynthetically active radiation to global radiation. The ratio of ultraviolet radiation to global radiation is influenced by the concentration of fine particles in aerosol. There is a negative correlation between fine aerosol concentration and the ratio of ultraviolet radiation to global radiation during the dust storm period. But the photosynthetically active radiation has the same variable trend as the global radiation during the dust storm period. The dust storm can be divided into three stages, namely, accumulation of local fine particle pollutants, arrival of external particle, and clear-out of dust. In the second stage the ratio of PM2.5 to PM10 decreased significantly. The air was cold and dry with low pressure during the dust storm. When the dust was cleared out the pressure increased rapidly. The variation characteristics of Ultraviolet radiation in Beijing city are analyzed by using the radiation data observed from 2004 to 2005. The daily, monthly and yearly variation characteristics of ultraviolet are same as global variation. The ratio of Ultraviolet radiation to global radiation varies from the maximum of 0.041 to the minimum 0.02. The ratio of ultraviolet radiation to global radiation in rainy day and dusty day are 0.041 and 0.02 respectively. Relation between ultraviolet radiation and the atmospheric clearness index is analyzed. For the clearness index is above 0.6, the ratio of ultraviolet radiation to global radiation keeps a constant values of 0.03. For the clearness index below 0.6, there is no evident relation between them. An experiential Ultraviolet radiation estimated model is developed using the atmospheric mass and global radiation. The estimation equation can be used to calculate ultraviolet radiation from global radiation with a relative error within 9%. Timescale variability of the ratio of Photosynthetically active radiation (PAR) to global radiation (Rs) is determined with the measured data. The ratio has a significant diurnal and seasonal variation trend .The daily ratio ranges from 1.42 to 2.57μmol J-1,the monthly from 1.657 to 2.039μmol J-1,and the seasonal from 1.705 to 1.990μmol J-1, with an annual mean value of 1.824μmol J-1.The characteristics of the ratio are mainly controlled by vapor content in the atmosphere. Atmospheric aerosol has no influence on the variation characteristics of the ratio. The estimation equation developed in this study can be used to calculate PAR values from global radiation measurements with a relative error within 10%. The spatio-temporal distribution characteristics of Ultraviolet radiation in china areanalyzed with the data observed in one year. The Ultraviolet radiation is increased from east to west in most part of China. In the western area it increases from north to south. The Ultraviolet radiation is lowest in the Changjiang River area and increases to the north and the south of this area. The Ultraviolet radiation decreases with the latitude increasing ,in northeast of China. The highest value appears in summer (July) and the lowest appears in winter (January). The ratio of Ultraviolet radiation to global radiation has distinct spatio-temporal variation characteristics in China. The highest value appears in summer (June and July) and the lowest appears in autumn (November). The value of the ratio increases from February in most area of China, especially in the Yellow River region and the region to the north of it. The highest value of the ratio appears in summer (June and July), and the ratio decreases from August. This variation characteristic is distinct in winter and spring. The clear index is an indication parameter of the ratio of ultraviolet to global radiation in whole China. For the clearness index is above 0.6, the ratio of ultraviolet radiation to global radiation is changeless. For the clearness index below 0.6, there is great scattering in the ratio. The ratio has a significant diurnal variation in whole China except for the southwestern region. A low ratio value appears in the morning and a high value appears around noon, and then it tends to decrease in the afternoon. The spatio-temporal distribution characteristics of photosynthetically active radiation (PAR) in china are similar as that of ultraviolet radiation. The ratio of PAR to Rs has a significant seasonal variation. A high value appears in summer and a low value appears winter and autumn (sunny with dryness). Combination of the theory and practice is the main characteristic of this paper. A pyranometer calibration system and an Ultraviolet/photosyntheticallly active radiation calibration system are established successfully. The spatio-temporal distribution characteristics of ultraviolet radiation and photosynthetically active radiation in china are obtained based on the observation data. The calibration methods and results are useful for theory research and application.