Reply on RC2

Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> Changes of aerosol loadings and properties are of importance to understand atmospheric environment and climate change. This study investigates the characteristics and the long-term trends of aerosols of different sizes and types in Asia from 2000 to 2020, by considering multi-source aerosol data, novel analysis method and perspective, all this groundwork promote the acquisition of new discoveries that are different from the past. The geometric mean aggregation method is applied, and serial auto-correlation is considered to avoid overestimation of trend significance. Among regions in Asia, high values of aerosol optical depth (AOD) are mainly concentrated in East Asia (EA) and South Asia (SA), closely related to population density. The AOD in EA showed the most significant negative trend with a value of -5.28&times;10^-4 per year, mainly owing to decreases in organic carbon (OC), black carbon (BC), and dust aerosols. It is also worth noting that this observed large-scale decrease in OC and BC is a unique and significant phenomenon to region of EA, and mainly around China. By contrast, the aerosol concentrations in SA generally show a positive trend, with an increase value of AOD of 1.25&times;10^-3 per year. This increase is mainly due to large emission of fine-mode aerosols, such as OC and sulphate aerosol. Additionally, the high aerosol loading in north SA has lower AOD variability comparing with that of East China plain, revealing a relatively more persistent air pollution situation. Over the whole Asia region, the characteristics of percentage changes in different type AOD are increases in BC (6.23 %) and OC (17.09 %) AOD with a decrease in dust (-5.51 %), sulphate (-3.07 %), and sea salt (-9.80 %) AOD. Except for anthropogenic emission, the large increase in the percentage of OC is also owing to wild fires found in Northern Asia in the summer. Whereas, the different size AOD only shows slight changes in Asia, that small-size AOD decreases (-3.34 %), and the total AOD did not show a significant change, suggesting that, from a trend perspective, decreases in aerosol in recent years have mostly been offsetting earlier increases in anthropogenic emission over Asia. To summarize, the above findings analyse the comprehensive characteristics of aerosol distributions and reappraise the long-term trends of different aerosol parameters, which will greatly enhance the understandings of regional and global aerosol environment and climatology, as well as fill in the gaps and break through the limitation of past knowledge.