Pollution‐Clearing Induced Fog Suppression Even Under Extremely Humid Conditions Over North China Plain During 2013–2024

Abstract Fog and haze significantly affect visibility, air quality, and public health. Although haze pollution in the North China Plain has decreased in recent years, its effect on fog formation remains unclear. We find that despite an increase in extremely high‐humidity events, fog frequency has declined, and the fraction of high‐humidity periods that produced fog (fog efficiency) dropped by 90%. Regression results show that the reduction in PM 2.5 concentration plays a major role in fog suppression, contributing over 70%. Semi‐mechanistic modeling shows that fog formation shifted from being PM 2.5 ‐dominated during past high‐pollution periods (PM 2.5 > 100 μg/m 3 ) to being jointly influenced by PM 2.5 and aerosol hygroscopicity in the current pollution‐control era (PM 2.5 ∼ 50 μg/m 3 ). In the future cleaner era (PM 2.5 < 20 μg/m 3 ), fog formation will primarily depend on relative humidity and require supersaturation. These findings demonstrate the significant impact of pollution control on fog formation in the North China Plain.