Aerosol spatiotemporal dynamics, source analysis and influence mechanisms over typical drylands

As globally important dust source areas, drylands not only have extremely fragile ecosystems that are exceptionally sensitive to global climate change but also have important implications for global warming and carbon cycling. However, the detailed dryland aerosol characteristics are not clear, especially the influence mechanisms of dryland aerosols, which are poorly understood. In this paper, Utilizing the Xinjiang Uygur Autonomous Region (XJ) as a target area, based on high spatial resolution aerosol optical depth (AOD) data, combined with the trend analysis, backward trajectory, source analysis, and machine learning methods, we systematically analyzed the multiscale dynamic characteristics of aerosols in XJ over a long period. Simultaneously, we also quantitatively explored the source distributions of high aerosols at typical sites at different time scales. Furthermore, we discussed the specific effects of natural and anthropogenic factors on aerosols in XJ and its subregions. The results show that 72.45% of the AOD in XJ presents an increasing trend from 2000 to 2019, 27.56% of which passed the significance test, mainly concentrated in northern Xinjiang (NXJ). The AOD in southern Xinjiang (SXJ) is the largest (0.240 ± 0.154), followed by eastern Xinjiang (EXJ) (0.157 ± 0.038), and the AOD in NXJ is the smallest (0.134 ± 0.028); however, the AOD in NXJ has the most obvious increasing trend, peaking in 2011, and the AOD in XJ remains low and stable at 5000 m elevation and above. The backward trajectory shows that nearly half of the potential paths of high AOD in SXJ are from the Taklamakan Desert, most of the potential paths in NXJ are from transboundary transmission, mostly through exposed lake beds, and most of the potential paths in EXJ are from the northwest, with characteristics similar to those of NXJ. The exposed lake beds provide salt dust, which further exacerbates the complexity and hazards of aerosols in NXJ and EXJ. The potential source areas for AOD in SXJ are concentrated in the northeast of the target site, those in NXJ are concentrated in the west of the target site, and those in EXJ are in the northwest and east. The AOD in SXJ (63.92%) and EXJ (74.83%) or XJ (57.77%) is dominated by natural factors, whereas the magnitude of AOD in NXJ (84.01%) is largely explained by anthropogenic factors.