Abstract:

In the summer of 2023, the Hexi Corridor, northwest China experienced its most intense regional high-temperature drought in nearly 60 years, accompanied by frequent wind and dust events. Notably, on September 6—7, Minqin County recorded its most severe sandstorm in almost 40 years. This study investigates two significant sandstorm events (on August 16, on September 6—7) in the Hexi Corridor during the summer and autumn of 2023. The evolution of meteorological elements, synoptic conditions, and boundary layer characteristics preceding the events is analyzed. The sources and transport pathways of dust are determined using the HYSPLIT model’s backward trajectory analysis and Sunflower 8 dust monitoring. The findings are as follows: (1) The regional high temperatures and drought provided ample material conditions for sandstorm development. (2) Synoptic analysis reveals that low-pressure troughs between 65°-85°E and 50°-58°N, combined with a stepped trough pattern from eastern Xinjiang to the Hexi Corridor and mesoscale shear, contributed to the events. At 500 hPa, the cold center intensity was ≤−20 ℃; at 700 hPa, it was ≤0 ℃. The mid-level jet exceeded 20 m·s⁻¹, the low-level jet exceeded 14 m·s⁻¹, and the K index was ≥21 ℃. Convergence occurred below 700 hPa (divergence ≤-0.75×10⁻⁵ s⁻¹), and divergence occurred between 700-650 hPa (divergence ≥0.75×10⁻⁵ s⁻¹). Ascending motion was observed between 800-600 hPa with intensity ≤−0.6 hPa·s⁻¹. Below 700 hPa was a region of positive vorticity with intensity ≥0.75×10⁻⁵ s⁻¹. (3) When the dust source is primarily local, near-surface humidity is the key factor influencing sandstorm intensity. (4) Compared to spring events, sandstorms in summer and autumn require stronger vertical motion, higher wind speeds, and larger 3 h pressure differentials for formation.

Key words: strong sandstorms from summer to autumn, regional high temperature and drought, remote sensing monitoring, transmission characteristics, Hexi Corridor