## Results
### Effects of Clouds  
In this study, the cloud vertical frequency is defined as the ratio of the number of cloud bins to the total number of observed bins by CloudSat at different heights, referring to a previous study [(47)]. The cloud vertical frequency sequentially decreased during the monsoon season in South Asia from 2006 to 2015, with a maximum decrement of 7.1% (Figure 2a). In general, the cloud water content and number concentration of liquid and ice under cloudy conditions consistently decreased, with maximum decrements of 18.0 mg m\({}^{-3}\) and 1.4 mg m\({}^{-3}\) of liquid and ice water content (Figure 2b,e), and approximately 6.0 cm\({}^{-3}\) and 2.0 L\({}^{-3}\) of liquid and ice number concentration (Figure 2d,g), respectively. However, the liquid and ice effective radius variations were indistinct and inconsistent with the changes in cloud water content and number concentration. Therefore, the cloud vertical frequency decreased with the reduced cloud water content and number concentration, but no clear change was observed in the particle effective radius during the monsoon season in South Asia from 2006 to 2015. In Figure 3a, the total cloud fraction detected by CloudSat declined by 8.8% (\(p\) = 0.07) during the monsoon season in South Asia from 2006 to 2015. Furthermore, the change in cloud water path (CWP, which is the sum of the liquid and ice water paths) under cloudy conditions was consistent with that of the total cloud fraction with a decrement of 34.7 g m\({}^{-2}\) (\(p\) < 0.01). The uppermost cloud top height (CTH) declined by 661 m (\(p\) = 0.08), and the cloud geometrical depth (CGD) declined by 280 m (\(p\) = 0.21) with partial fluctuations in 2009 and 2010 (Figure 3b). By contrast, an insignificant trend occurred in the lowermost cloud base height (CBH) variation. Then, we further analyze the spatial variations in cloud fraction, cloud height (CH, which is the mean of corresponding CTH and CBH), CWP, and CGD. Figure 3c-f illustrate the consistent decreases in cloud fraction, CH, CWP, and CGD, especially for the cloud fraction and CWP with significant and consistent changes in space. The CH and CGD increased in certain parts of the western coastal area in South Asia. Overall, we can conclude that clouds decreased and thinned with the reduction in water content and particle number concentration (Figure 2) during the monsoon season in South Asia from 2006 to 2015, thereby weakening the regulation of cloud on radiation. Figure 3: Temporal variations in spatial average (**a**) cloud fraction and CWP, as well as (**b**) uppermost CTH, lowermost CBH and CGD; spatial distributions of the temporal changes in average (**c**) cloud fraction, (**d**) CH, (**e**) CWP, and (**f**) CGD from CloudSat during the monsoon season in South Asia from 2006 to 2015. The dashed lines indicate the linear fit line of the solid line with the same color; \(p\) is the significance level. Figure 2: Temporal variations in spatial average vertical cloud physical parameters from CloudSat during the monsoon season in South Asia from 2006 to 2015: (**a**) cloud vertical frequency distribution, and liquid and ice (**b**,**e**) water content, (**c**,**f**) effective radius, and (**d**,**g**) number concentration. The factors that contribute to the changes in clouds are complicated and varied in South Asia. [PERSON], et al. [48] verified that aerosols with intensive absorption may lead to evaporation in the cloud layers (the aerosol semi-direct effect), thereby burning off the clouds in South Asia, including widespread dust, polluted dust, and smoke. [PERSON], et al. [49] highlighted that anthropogenic aerosol emissions weaken the South Asian summer monsoon, thereby causing a decrease in the occurrence and amount of precipitation. Globally, observed and simulated cloud change patterns at the global scale are consistent with the poleward retreat of mid-latitude storm tracks. This result is attributed to the increase in greenhouse gas concentrations and recovery from volcanic radiative cooling [50].