How mountain downslope and plain thunderstorms interact in Beijing region

The unique geographical conditions and political status of Beijing underscore the significance of intensifying research on thunderstorm weather in the region. Previous studies have predominantly focused on squall line systems, with relatively limited investigation into the merger processes of thunderstorm clusters in Beijing’s plain and downslope regions.

Recently, researchers from NUIST (Nanjing University of Information Science and Technology) and IAP CAS (Institute of Atmospheric Physics, Chinese Academy of Sciences) analyzed a specific downslope thunderstorm merger process with the aim to provide a valuable scientific reference for short-term forecasting in the Beijing area. The study has been published in Atmospheric and Oceanic Science Letters.

Utilizing simulation data from the Weather Research and Forecasting Model for a convection event on 23 August 2021, the analysis revealed that differences in pre-storm wind fields and thermodynamic conditions impeded the movement and cold pool development of the mountainous thunderstorm cluster, while the plain thunderstorm cluster experienced the opposite effect. Ultimately, the clusters merged at the mountain base, where the enhanced cold pool acted analogously to topographical features, strengthening convergence and vertical motion.

Prior to merger, the low-level negative thermal buoyancy suppressed the development of vertical motion in the mountainous thunderstorm cluster, while the plain thunderstorm cluster’s low-level positive perturbation vertical pressure gradient force accelerated upward motion. Post-merger, the bottom-layer positive perturbation vertical pressure gradient force and low-level positive thermal buoyancy collaboratively drove the development of vertical motion.

In future work, the researchers will conduct a comparative analysis of environmental conditions and developmental mechanisms across different cases of downslope weakening, downslope intensification, and downslope persistence.