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Synergistic mechanisms of gravity waves and windward slopes in intensifying regional rainstorms: A Sichuan Basin case study
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DOI：10.1016/j.atmosres.2026.109028.png)
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Abstract
En 中文
Slope topography is conducive to triggering gravity waves and can also act as the windward slope, enhancing updrafts. Gravity waves and windward slopes may synergistically enhance precipitation. In this study, based on potential vorticity thinking, the synergistic enhancement effect of the windward slopes of the Daba Mountain and Wuling Mountain, and two gravity waves triggered by the Western Sichuan Plateau and Yunnan-Guizhou Plateau on precipitation is analyzed. Results show that flow-over and flow-around motions caused by the peak-valley terrain on the plateau, together with gravity wave drag, jointly weaken the horizontal wind speed near the ground, and enhance the vertical wind shear between the upper and middle troposphere, which is conducive to the excitation and maintenance of large-amplitude gravity waves formed in the upper troposphere by the shear instability mechanism. Compared to the smoothed plateau terrain, the presence of small-scale, high-frequency topographic features can excite gravity waves with larger amplitudes and longer durations, forming stronger, chain-like distributed heating centers, which results in the rapid strengthening of positive potential vorticity anomalies in the upper troposphere. After these anomalies merge with the positive potential vorticity area caused by the heating center near the windward slope of the lower troposphere, more vigorous deep convection is formed. As the windward slope, the Daba Mountains enhance updrafts through topographical lifting and boundary-layer convergence, thereby strengthening latent heat release in the lower troposphere and enhancing positive potential vorticity near the windward slope. In contrast, the potential vorticity enhancement effect of the Wuling Mountains as the windward slope is relatively small. The intensification of diabatic heating reduces atmospheric pressure, facilitating the formation of the Southwest Vortex circulation.
Keywords:
Sichuan Basin
Rainstorm
Gravity wave
Southwest Vortex
Terrain effect
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