ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-10-18389-2010 Solar radiation trend across China in recent decades: a revisit with quality-controlled data Tang W.-J. 1 2 Yang K. 1 Qin J. 1 Cheng C. C. K. 3 He J. 1 2 Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, China Graduate School of Chinese Academy of Sciences, Beijing 100049, China Department of Building and Construction, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong 03 08 2010 10 8 18389 18418 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/10/18389/2010/acpd-10-18389-2010.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/10/18389/2010/acpd-10-18389-2010.pdf

Solar radiation is one of the most important factors affecting climate and environment, and its long-term variation is of much concern in climate change studies. In the light of the limited number of radiation stations with reliable long-term time series observations, this paper presents a new evaluation of the long-term variation of surface solar radiation over China by combining quality-controlled observed data and two radiation models. One is the ANN-based (Artificial Neutral Network) model and the other is a physical one. The two models produced radiation trends comparable to the observed ones at a few stations possessing reliable and continuous data. Then, the trend estimation is extended by the ANN-based model to all 96 radiation stations and furthermore extended by the physical model to all 716 China Meteorological Administration (CMA) routine stations. The new estimate trend is different from previous ones in two aspects. First, the magnitude of solar radiation over China decreased by about −0.19 W m<sup>−2</sup> yr<sup>−1</sup> between 1961 and 2000, which is greatly less in magnitude than trends estimated in previous studies (ranging over −0.41 to −0.52 W m<sup>−2</sup> yr<sup>−1</sup>). Second, the "From Dimming to Brightening" transition in China during the late 1980s and the early 1990s was addressed in previous studies, but this study indicates the solar radiation reached a stable level since the 1990s and the transition is not noticeable. These differences are attributed to inappropriate data and approaches in previous studies.

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