Abstract
Aerosol optical depth (AOD), which represents the optical attenuation, poses a major threat to the production activity, air quality, human health and regional sustainable development of arid and semi-arid areas. To some degree, AOD shows areal air pollution level and possesses obvious spatio-temporal characteristics. However, long-time sequences and detailed AOD information can not be provided due to currently limited monitoring technology. In this paper, a daily AOD product, MODIS-based Multi-angle Implementation of Atmospheric Correction (MAIAC), is deployed to analyze the spatio-temporal characteristics in Xinjiang Uygur Autonomous Region from 2000 to 2019. In addition, the importance of influencing factors for AOD is calculated through Random Forest (RF) Model and the propagation trajectories of pollutants are simulated through Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) Model. Spatio distribution of AOD presents a tendency that AOD value in northern Xinjiang is low while the value in southern Xinjiang is high. Regions with high AOD values are mainly concentrated in Tarim Basin. AOD in southern Xinjiang is the highest, followed by that in eastern Xinjiang and AOD value in northern Xinjiang is the lowest. Seasonal variation of AOD is significant: Spring (0.309) > summer (0.200) > autumn (0.161) > winter (0.158). Average AOD value in Xinjiang is 0.196. AOD appears wavy from 2000 to 2014 with its low inflection point (0.157) appearing in 2005, and then increases, reaching its peak in 2014 (0.223). The obvious downward tendency after 2014 shows that the use of coal to natural gas (NG) conversion project improves the conditions of local environment. According to RF Model, NG contributes most to AOD. HYSPLIT Model reveals that aerosol in southern Xinjiang is related to the short-distant carriage of dust aerosol from the Taklimakan Desert. Aerosol there can affect Inner Mongolia through long-distant transport. Blocked by the Tianshan Mountains, fine dust particles can not cross the Tianshan Mountains to become a factor contributing to AOD in northern Xinjiang.
Highlights
As a primary element of the atmosphere, atmospheric aerosol is the generic term of heterogeneous system made up of solid and liquid particles suspending in the gas [1], whose mass is only a billionth of that of the atmosphere
The biggest contribution of mixed aerosols is created in spring and summer [30]. These results show that contribution of dust to aerosol in Xinjiang and Central Asia is significant, and the spread and migration of aerosol affect the whole Xinjiang and Central Asian, which is of practical significance
Decisive coefficient (R2), root mean square error (RMSE) and mean absolute error (MAE) indicators are applied to value the implementation of the estimates
Summary
As a primary element of the atmosphere, atmospheric aerosol is the generic term of heterogeneous system made up of solid and liquid particles suspending in the gas [1], whose mass is only a billionth of that of the atmosphere. Aerosol is used extensively as an uncertain but important indicator of the research on climate change and radiation equilibrium of atmosphere [6,7,8]. AOD exerts great influence on climate regionally and even globally, atmospheric radiation transmission, as well as water circulation [9,10,11]. Dust aerosols account for one-third of atmospheric aerosols [12] and the strong heating or cooling effect caused by its changes will alter the thermal condition of the atmosphere, affecting the dynamic structure of the atmosphere [13]
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