乌苏市冬季短时内两次强沙尘过程气象条件及来源对比分析

Comparative Analysis of Meteorological Conditions and Source Contributions of Two Strong Sand and Dust Events in Wusu City during Winter

摘要: 本研究针对2025年冬季新疆乌苏市相继发生的“1·23”与“2·25”两次强沙尘过程，综合运用地面气象观测、ERA5再分析资料、颗粒物浓度监测及后向轨迹模拟等方法，从天气系统、动力结构、前期地表条件与污染物来源等角度展开系统对比。结果表明：“1·23”过程受“北槽南涡”型高低压对峙系统控制，850 hPa层呈现强辐合(散度达−2 × 10⁻⁵ s⁻¹)与高螺旋度(250 m²∙s⁻²)，动力抬升显著，属于以中远距离输送为主的“多源复合型”沙尘；而“2·25”过程则为冷高压前缘锋面爆发型，动力结构较弱，沙尘起沙更依赖局地强风，属“局地主导型”。两次过程发生前均具备显著的“暖–干”型前期气候背景，地表气温偏高1.5℃~3℃，降水偏少1~5 mm，土壤湿度下降0.12~0.20 m³/m³，共同导致地表可蚀性显著增强。轨迹聚类与浓度权重分析进一步表明，“1·23”过程沙尘来源于本地、哈萨克斯坦东南部和新疆西南部三类源区，外源输送占比较高；而“2·25”过程则以乌苏本地及西南近源区为核心(轨迹占比70.83%，WCWT值 > 500 μg∙m⁻³)，外源影响微弱。研究阐明了两类沙尘过程在天气背景、动力机制与源区结构方面的本质差异，为北疆地区冬季沙尘天气预报及差异化防控策略的制定提供了科学依据。

Abstract: This study focuses on the two strong sand and dust events that occurred successively in Wusu City, Xinjiang in winter 2025, namely the “1·23” and “2·25” events. By integrating ground meteorological observations, ERA5 reanalysis data, particulate matter concentration monitoring, and backward trajectory simulations, a systematic comparison was conducted from the perspectives of weather systems, dynamic structures, pre-event surface conditions, and pollutant sources. The results show that the “1·23” event was controlled by a “north trough-south vortex” type of high-low pressure confrontation system, with strong convergence (divergence reaching −2 × 10⁻⁵ s⁻¹) and high vorticity (250 m²∙s⁻²) at the 850 hPa layer, indicating significant dynamic uplift. It was a “multi-source composite type” sand and dust event mainly driven by long-distance transport. In contrast, the “2·25” event was a cold high-pressure front-type event with a weaker dynamic structure, where local strong winds played a more significant role in sand lifting, making it a “locally dominant type” event. Both events were preceded by a significant “warm-dry” type of pre-event climate background, with surface temperatures 1.5˚C ~3˚C higher, precipitation 1~5 mm less, and soil moisture decreased by 0.12~0.20 m³/m³, collectively leading to a significant increase in surface erodibility. Trajectory clustering and concentration-weighted trajectory (WCWT) analysis further indicated that the “1·23” event’s sand and dust originated from three source areas: local, southeastern Kazakhstan, and southwestern Xinjiang, with a relatively high proportion of external transport. In contrast, the “2·25” event was centered on Wusu and its southwestern near-source areas (trajectory proportion 70.83%, WCWT value > 500 μg∙m⁻³), with minimal external influence. This study clarifies the essential differences between the two types of sand and dust events in terms of weather background, dynamic mechanisms, and source area structures, providing a scientific basis for winter sand and dust weather forecasting and the formulation of differentiated control strategies in the northern Xinjiang region.