Observed multiscale dynamical processes responsible for an extreme wind gust event in Beijing

Abstract. Extreme wind gusts pose substantial threats to human safety and infrastructure, yet pre-onset observational constraints remain inadequate, leading to large uncertainties and inaccuracies in nowcasting and prediction. To address this gap, we conduct an in-depth investigation of a record-breaking surface gust event (wind speed >35 m s⁻¹) that occurred in Beijing during the early afternoon of 30 May 2024. We explore the dynamical characteristics of this event utilizing a high-resolution meteorological mesonet, which includes seven radar wind profilers, a meteorological tower, automated weather stations, radar and satellite data. Multi-source observational analyses show the development of multicellular storm ahead of the convergence line as the northeasterly cold outflows met environmental southerly winds during its downhill propagation. Evaporative cooling contributed to the generation of the extreme winds through the downward momentum transport and pressure gradient forcing. After reaching the plain, two convective segments subsequently merged into a well-organized squall system embedded with a midlevel mesovortex with intense rear-inflow jet. The emergence of low-level frontogenesis and shearing deformation provided favorable conditions for sustaining mesoscale convection. This mesoscale convection then fueled small-scale turbulent energy processes. The inverse energy cascades of turbulence – a process involving energy transfer from small to large eddies – significantly intensified as wind speeds increased markedly. This study offers valuable insights into the multiscale dynamical processes governing extreme gust wind events. Moreover, these findings underscore the value of RWP mesonet observations for enhancing our understanding of extreme wind events and in improving the nowcasting and prediction efforts in the future.