Abstract:On 28 December 2022, multiple vehicle collisions occurred on the Zhengxin Yellow River Bridge due to heavy fog. Based on ERA5 reanalysis and surface observation data, the method of disturbance-based synoptic analysis is used to diagnose and analyze the heavy fog episode. The results show that the heavy fog weather had the characteristics of strong local suddenness, low visibility, and significant nighttime cooling. The low visibility caused by heavy fog and the ice and slippery bridge deck caused by high humidity and low temperature were the meteorological reasons for the vehicle rear-end collision accidents. The synoptic conditions were stable, with weak cold air at the bottom and warm ridges in the southwest transport of warm and humid airflow into the foggy area, and the circulation pattern was favorable for the generation of fog. The water vapor flux near the bridge was high, and there existed weak water vapor convergence, shallow inversion layer and strong radiation cooling effect, which provided favorable dynamic, water vapor, and thermal conditions for the occurrence and persistence of radiation fog. The disturbance signals of wind speed, relative humidity, temperature and specific humidity can better reflect the predictable signals of heavy fog compared to the corresponding disturbance signals. The comprehensive analysis of multiple disturbance factors can help determine the dissipation time of fog.