Impacts of 3D Aerosol, Cloud, and Water Vapor Variations on the Recent Brightening during the South Asian Monsoon Season  
[PERSON]  
1 State Key Laboratory of Information Engineering in Surveying, Mapping, and Remote Sensing, Wuhan University, Wuhan 430079, China; [EMAIL_ADDRESS] (Z.P. ); [EMAIL_ADDRESS] (W.W.); [EMAIL_ADDRESS] (X.L. ); [EMAIL_ADDRESS] (W.G. )1  
[PERSON]  
1 State Key Laboratory of Information Engineering in Surveying, Mapping, and Remote Sensing, Wuhan University, Wuhan 430079, China; [EMAIL_ADDRESS] (Z.P. ); [EMAIL_ADDRESS] (W.W.); [EMAIL_ADDRESS] (X.L. ); [EMAIL_ADDRESS] (W.G. )1  
[PERSON]  
1 State Key Laboratory of Information Engineering in Surveying, Mapping, and Remote Sensing, Wuhan University, Wuhan 430079, China; [EMAIL_ADDRESS] (Z.P. ); [EMAIL_ADDRESS] (W.W.); [EMAIL_ADDRESS] (X.L. ); [EMAIL_ADDRESS] (W.G. )1  
[PERSON]  
5 School of Remote Sensing and Information Engineering, Wuhan University, Wuhan 430079,  
global solar radiation is no longer declining at many sites since the late 1980s [2]. [PERSON], et al. [5] found that solar dimming has reversed at an increasing trend of 6 W m\({}^{-2}\) per decade in the continental United States from 1995-2007. [PERSON] [6] showed that the globally averaged trends in the 1980s typically reversed from dimming to brightening, while this study reports trends of 2.2-6.6 W m\({}^{-2}\) per decade from the 1980s to the 2000s. However, developments in dimming and brightening after 2000 have shown mixed tendencies. [PERSON], et al. [7] reported a continuation of brightening at sites in Europe, United States, and parts of Asia, a levelling-off at sites in Japan and Antarctica, and indications of renewed dimming in China. Conversely, a recent and related study shows that brightening has continued in China since 2000 [8]. South Asia is endowed with abundant solar energy, given the geographic position of this region in the tropical belt [9]. Dimming or brightening is more evident and complicated in South Asia than in other regions, and its effects on regional and global climate and ecosystems are amplified by monsoon circulation (between June and September) in the region [1; 10]. Although solar dimming had reversed after the late 1980s in other regions globally, [PERSON], et al. [10] found that the continued dimming of \(-8.6\) W m\({}^{-2}\) per decade had occurred in India from 1981 to 2004 based on 12 stations over the Indian region. However, [PERSON], et al. [7] proposed to focus on the slight tendency towards the stabilizing of surface solar radiation that possibly began in the late 1990s. Furthermore, [PERSON], et al. [9] observed a trend reversal and partial recovery from dimming to brightening in India around 2001, but the related reasons are not determined. Various mechanisms potentially contribute to dimming and brightening. Changes in surface solar radiation can be caused by either external changes in the amount of solar radiation incidents on the planet at the top of the atmosphere (TOA) or internal changes (within the climate system) in the transparency of the atmosphere, thereby modifying the solar beam on its way to the Earth surface. However, [PERSON] and [PERSON] [11] verified that decadal dimming or brightening cannot be explained by changes in the luminosity of the sun because these changes are at least an order of magnitude smaller than those in climate systems. Therefore, the observed dimming or brightening must originate from alterations in the transparency of the atmosphere. Such alterations depend on the presence of clouds, aerosols, and radiatively active gases, particularly water vapor, which is a strong absorber of solar radiation [12]. [PERSON] and [PERSON] [13] concluded that the major contributor to dimming, since pre-industrial times, is aerosols (\(-2.4\) W m\({}^{-2}\)) and that the secondary effect is the increase in gas concentrations (\(-0.64\) W m\({}^{-2}\)), including those of tropospheric ozone and water vapor. They also identified NO\({}_{2}\), CH\({}_{4}\), and CO\({}_{2}\) as minor contributors.