Spatial and temporal distribution characteristics of low-visibility phenomena in Xinjiang based on instrument measurements

Low-visibility phenomena strongly impact the environment, as well as transportation, aviation and other fields that are closely related to people's livelihoods; thus, they represent important ecological issues of social concern. Based on observation data concerning low-visibility phenomena derived from 105 national meteorological stations in Xinjiang, China over the past 20 years, we systematically analyzed the differences between manual and instrument observations for six types of low-visibility phenomena, with a focus on exploring their spatiotemporal distribution characteristics using instrument data. The results revealed that low-visibility phenomena were dominated by fog- and haze-related events (mist, fog, and haze) in northern Xinjiang and dust-related events (dust storms, blowing sand, and floating dust) in southern Xinjiang, with transitional characteristics observed in eastern Xinjiang. Compared with manual observations, the instrument measurements significantly improved the fine-scale low-visibility phenomenon identification process. On the basis of the instrument observation data, spatial-dimension analysis results indicated that low-visibility phenomena in Xinjiang were significantly influenced by terrain factors. Constrained by the Tianshan Mountains, haze-like phenomena formed a core agglomeration area in northern Xinjiang, whereas dust- and sand-related phenomena radiated outward, with the Taklimakan Desert at the center. Moreover, the gripping effect of the terrain promoted dust transmission along low-altitude channels. Temporally, fog- and haze-related phenomena occurred mainly during autumn and winter, and the proportion of these events decreased from 76.7% to 55.1%. The fog- and haze-related phenomena demonstrated a U-shaped rebound trend, while the proportion of mist phenomena decreased by 34.2%. Dust storms occurred during spring, accounting for 23.3% to 44.9% of all storms. Instrument measurement technology has the advantages of high spatial and temporal resolutions and multiparameter coordination but provides a limited dust–haze mixed-pollution identification capacity. This study provides crucial reference data for enhancing the understanding of low-visibility events in Xinjiang and the potential responses while improving the accuracy of pollution source tracking and meteorological process diagnosis tasks.