Urbanization amplifies dimming: Unraveling the drivers of reduced solar radiation in Beijing

Abstract Beijing's urbanization process may alter clouds, water vapor, and aerosols, which in turn influences surface incident solar radiation ( R s ). This study quantifies the urban–rural differences in R s , and explores the effects of clouds, water vapor, and aerosols on urbanization‐induced radiation effects. Ridge Regression Analysis was used as it effectively reduces the multicollinearities among factors. It is found that the urban–rural R s trend difference progressively increased, from −0.57 W·m −2 ·10 years −1 for 1960–1984 to −2.43 W·m −2 ·10 years −1 for 1985–1999, and then reversed to −0.50 W·m −2 ·10 years −1 for 2000–2013. The urbanization radiative effects were particularly pronounced for the first two periods, accounting for 40.97% and 42.24%, respectively, but reduced to 19.51% for 2000–2013. Overall, urban R s decreased faster than rural R s , which is mainly due to urban–rural difference in aerosol (26.8%) and water vapor (25.4%) for 1960–1984, aerosol (29.7%) and low cloud cover (28.4%) for 1985–1999, and total cloud cover (28.6%), low cloud cover (29.2%) and aerosol (26.3%) for 2000–2013 according to Ridge Regression Analysis. This study highlights a comprehensive understanding of the urbanization effect on the R s in megacities.