Location: Northwest Watershed Research CenterTitle: Changes in the relationship between solar radiation and sunshine hours in large cities of China
|LIU, JIANDONG - Chinese Academy Of Sciences|
|HANS, LINDERHOLM - Lund University|
|DELIANG, CHEN - Lund University|
|XIJI, ZHOU - Chinese Academy Of Sciences|
|QIANG, YU - Chinese Academy Of Sciences|
|JUN, DU - Chinese Academy Of Sciences|
|DINGRONG, WU - Chinese Academy Of Sciences|
|YANBO, SHEN - Chinese Academy Of Sciences|
|ZHENBIN, YANG - Chinese Academy Of Sciences|
Submitted to: Energy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2015
Publication Date: 2/18/2015
Citation: Liu, J., Hans, L., Deliang, C., Xiji, Z., Flerchinger, G.N., Qiang, Y., Jun, D., Dingrong, W., Yanbo, S., Zhenbin, Y. 2015. Changes in the relationship between solar radiation and sunshine hours in large cities of China. Energy. 82(15):589-600.
Interpretive Summary: The intensity of solar radiation is critical input to many ecological and hydrological models and to the design of solar-powered systems, but it is not a commonly measured variable at most meteorological stations. Algorithms exist to estimate solar radiation from commonly observed meteorological variables, but the relationships may have changed in some areas due to increased aerosols and pollution in the atmosphere. This hypothesis was confirmed based on the analysis of data from six large Chinese cities. Based on the findings of this research, a 10 year data set is recommended to establish relationships for estimating solar radiation in rapidly developing regions rather the longest data set obtainable. This should provide more reliable estimates of solar radiation for model input and solar power design.
Technical Abstract: Based on the linear relationship between solar radiation and sunshine hours, the Angstrom model is widely used to estimate solar radiation from routinely observed meteorological variables for energy harvest. However, the relationship may have been changed in the rapidly developing regions in the recent decades, with increasing aerosols due to industrial pollutions. Solar radiation stations under different climate conditions in six large cities in China were selected to test this hypothesis. Primary analysis of the related meteorological items showed that Guiyang has the lowest solar radiation with the average annual value of 10.5MJm-2d-1, while Lhasa on the Tibetan Plateau has the highest of 20.1MJm-2d-1. Both radiation and sunshine hours decreased from 1961 to 2010, but with different decreasing rates. A moving linear regression method was introduced to investigate the changes in the relationship between radiation and sunshine hours, and the results indicated a vivid abrupt change in correlation coefficients in 1980-1990s, which can be attributed to the aerosols resulting from air pollution raised by the industrial development in 1980s with China’s Open Door Policy. The sky condition has changed from clean to dirty, thus the relationship between solar radiation and sunshine hours changes in the 1980’s and has reconstructed in recent decades. This finding implies that it might not be correct for the intuitive tendency of using the longest possible data sets for model calibration, and further investigation confirmed that Angstrom model performed the best with higher Nash-Sutcliffe Efficiency (NSE) of 0.914 and lower Mean Absolute Percentage Error (MAPE) and Root Mean Square Error (RMSE) vale of 13.7 Jm-2s-1 and 23.9 Jm-2s-1 respectively, when calibrated with 10 year data set. In contrast, the model performed worst when calibrated with 40 year data set, with NSE, MAPE and RMSE value of 0.891, 15.131 Jm-2s-1 and 25.297 Jm-2s-1, respectively. Based on the findings of this research, a 10 year data set is recommended as the national standard for model calibration in rapidly developing regions of China. Further analogous investigations are needed in other industrial regions to make an international standard for Angstrom model calibration.