Synergistic Effects of an Interlaced Mountain–Lake–Plain Terrain on Wintertime PM _2.5 Pollution in Central China

Abstract

The role of plain–lake–mountain mixed terrain surfaces on fine particle (PM _2.5 ) pollution is still unclear. Here, a Weather Research and Forecasting model coupled with Chemistry modeling study was designed for a winter PM _2.5 pollution episode in Central China with two lakes and surrounding mountains. A control experiment with three sensitive experiments were conducted to investigate how topography and lakes influence PM _2.5 and associated chemical components through impacting boundary‐layer dynamics and thermal structure. Results show that the surrounding mountains strongly suppress boundary‐layer turbulent mixing via terrain‐induced subsidence and blocked regional airflow, reshaping boundary‐layer circulation into recirculation cells. This causes a ∼120 m reduction in planetary boundary layer height (PBLH) at the pollution peak and a 3.5 µg m ⁻³ (+3.8%) domain‐wide increase in average PM _2.5 (up to ∼21 μg m ⁻³ higher at the pollution peak). Lake effects on PM _2.5 are weak (−0.2% on average) but highly heterogeneous. Poyang Lake's high thermal inertia reduces daytime heating, promotes the stabilization of a cold‐humid near‐surface layer, which in turn suppress local PBLH by 300.6 m (−85.1%) relative to a No Lake scenario and increases PM _2.5 concentrations by 36.8 μg m ⁻³ (+19.9%). In contrast, the smaller Dongting Lake induces daytime lake breezes and upward motion that enhance mixing and ventilation downwind, locally lowering PM _2.5 by 29.2 µg m ⁻³ (−11.9%). This study highlights the compound topography‐lake effects on winter PM _2.5 pollution and its spatial heterogeneity, providing a scientific basis for air‐pollution mitigation over complex‐terrain.