[A-AS03] Extreme Events and Mesoscale Weather: Observations and Modeling

[AAS03-12] Numerical Simulation and Mechanism Study of Foehn in Beijing

*Xingcan Jia¹ (1.Institute of Urban Meteorology, Chinese Meteorological Administration, Beijing, China)

Keywords:Foehn, Leewave, Numberical Simulation

The foehn wind is a localized dry and warm wind phenomenon resulting from the descent of air on the leeward side of mountains. It is characterized by elevated temperatures, low humidity, and strong gusty winds. The Beijing region, influenced by the Taihang Mountains, is a high-frequency area for foehn events. Due to the interplay of complex topography and meteorological conditions, as well as the small spatial scale of foehn dynamics, accurate prediction remains a significant challenge. Due to the interplay of complex topography and meteorological conditions, as well as the small spatial scale of foehn, accurate prediction remains a significant challenge. This study analyzes a foehn event that occurred in the Beijing region on January 4, 2024, through observational data analysis and numerical sensitivity experiments. (1) The west airflow crossing the mountains triggered lee waves, causing the air to descend and warm on the leeward side, thereby forming a typical warm and dry foehn. The foehn moves with the propagation of the lee waves. Stations in the Beijing area experienced a gradual temperature increase from northwest to southeast, accompanied by a noticeable strengthening of the northwest airflow and an increase in vertical wind speed. (2) Increasing the model resolution to 1 km significantly improved the simulation of lee waves. The higher-resolution model captured stronger vertical air motions and better represented the contribution of near-surface airflow to ground-level warming, thereby enhancing the accuracy of foehn simulation and reproducing the observed surface warming patterns.