## 5 Conclusions  
We use observations from multiple satellites/sensors in the A-Train satellite constellation to evaluate the impacts of 3D aerosol, cloud, and water vapor variations on the recent changes in solar radiation on the Earth's surface during the monsoon season (June-September) in South Asia from 2006 to 2015. The satellites used mainly include CloudSat, CALIPSO, MODIS, and CERES. We illustrate the results of this study in Figure 10 and summarize these results as follows. We found that the SSR possibly increased by 16.2 W m\({}^{-2}\) with a partial fluctuation based on the CERES observation during the monsoon season. By contrast, the increase in aerosol loading (mainly below 2 km) was inconsistent with the SSR variation and did not contribute to the recent brightening in  
Figure 9: Temporal variations in (**a**) spatial average AOD from MODIS and (**b**) SSR from CERES during the pre-monsoon, monsoon, and dry seasons in South Asia from 2006 to 2015, respectively. The dashed lines indicate the linear fit line of the solid line with the same color; \(p\) is the significance level. South Asia. Decreases in water vapor amount and clouds significantly contributed to solar brightening and, possibly, subsequent surface warming in South Asia. In general, the clouds are reduced and thinned by approximately 8.8% and 280 m, respectively, when the CWP (by 34.7 g m\({}^{-2}\)) and particle number concentration under cloudy conditions decreased. Correspondingly, the SW CRE weakened by approximately 42.1 W m\({}^{-2}\) at the surface. Moreover, the PW in clear-sky conditions possibly decreased by nearly 2.8 mm over the brightening period. The decreased PW is dominated by low-level water vapor (below 2 km), which decreased by 1.5 mm in clear-sky conditions with a high significance level. Consequently, solar brightening increased by approximately 2.5 W m\({}^{-2}\) because of the weakened absorption of water vapor in clear-sky conditions. The decreases in 3D water vapor amount and clouds weakened the effect of water vapor and clouds on solar radiation, thereby resulting in the increased absorption of direct solar radiation at the surface and subsequent surface brightening. The conclusions of this study are beneficial in evaluating the recent variations in 3D aerosol, cloud, and water vapor and their resultant impacts on solar radiation. Notably, the data in this study were from the instantaneous observations of multiple sensors. We then use the observations to ensure consistently observed conditions of multiple satellites from the A-Train. Thus, the magnitudes of radiative impact may be overestimated for the water vapor and cloud variations. The results are more representative of the atmospheric condition variations at nominally constant solar zenith angles than the daily average. Additionally, solar dimming and brightening may be of a local or regional nature [9]. The variations in aerosols, water vapor, and clouds highly interact with changes in monsoon circulation in South Asia. Thus, investigating the change mechanisms of aerosols, clouds, and water vapor in South Asia is interesting. The chicken-and-egg relationship between monsoon and aerosols, and water vapor and clouds can also be explored. The following are available online at [[http://www.mdpi.com/2072-4292/10/4/651/s1](http://www.mdpi.com/2072-4292/10/4/651/s1)]([http://www.mdpi.com/2072-4292/10/4/651/s1](http://www.mdpi.com/2072-4292/10/4/651/s1)), Table S1: Observations used in the analysis along with their sources and spatial resolutions, Figure S1: Terrain map during the monsoon season in South Asia and the surrounding regions. The blue line indicates rivers; the study region is within the red line. Figure 10: Schematic of the impacts of 3D aerosol, cloud, and water vapor variations on brightening during the monsoon season in South Asia from 2006 to 2015. Background gradient color represents the changing RH. The relative humidity is high when the color is dark.