A Revisit of Direct and Diffuse Solar Radiation in China Based on Homogeneous Surface Observations: Climatology, Trends, and Their Probable Causes
Yawen Wang, Su Yang, Arturo Sanchez‐Lorenzo, Wenping Yuan, Martin Wild
Abstract
Abstract Increasing energy and food demands require an understanding of not only the availability and variability of total solar radiation ( R ) but also its partitioning into direct ( R d ) and diffuse ( R f ) components, which are key elements for solar power generation and plant photosynthesis, respectively. Potential inhomogeneities in surface solar radiation observations, however, add uncertainties to the published patterns and trends of R d and R f over China. To exclude inhomogeneous time series and outliers, a data quality control process has been applied to the surface observations of R d and R f . The homogeneous data show that, in response to the global dimming and brightening phenomena in R , decadal changes can also be observed in the R d and R f trends over China with the actual transition occurring in the mid‐2000s. Since the 1960s, R d dimming has mainly distributed over eastern China with intensive anthropogenic activities, with recoveries especially from 2008 onward over regions with high R d energy potential. R f , on the other hand, had further enhanced since the 1960s especially over the high R f proportion areas but has decreased in the recent decade over the northern region. The summer season shows the most significant decadal trends in R d and R f . Under clear‐sky conditions, that is, ruling out cloud effects, the transitions in R d and R f trends become more remarkable, pointing to atmospheric aerosols as the main driving force. In addition, dramatic R d and R f variations are observed in the subsequent years after large volcanic eruptions. The varying R d and R f proportions are in line with recent governmental control on SO 2 emissions over China.