摘要：Nighttime ozone (O 3 ) reserved over the stable boundary layer (SBL) could contribute significantly to surface O 3 levels. While many studies have revealed that daytime convective eddies and turbulence induced by nighttime low‐level jets can mix O 3 ‐rich air over the SBL down to the surface, increasing nocturnal surface O 3 within the cloud topped boundary layer has rarely been examined. In this study, we used measurements and a single‐column photochemistry model to investigate O 3 variations within the nighttime cloud topped boundary layer over the Sichuan Basin, which is the cloudiest region in southwest China. The Santa Barbara Distort Atmospheric Radiative Transfer radiation model was coupled into the single‐column photochemistry model to investigate the nighttime radiative effects of clouds. The results showed that the nocturnal cloud top radiative cooling generated turbulence and enhanced vertical mixing below the cloud top layer. The cloud‐driven turbulent eddies even penetrated through the SBL to the surface. Consequently, it weakened the decoupling of the SBL from the residual layer. O 3 ‐rich air over the SBL was entrained downwards to the surface, decreasing O 3 aloft and increasing surface O 3 at nighttime. The cloud top radiative cooling rates were enhanced with the increase in the cloud liquid water path. Higher cooling rates produced stronger turbulent transport of O 3 , leading to higher nocturnal surface O 3 levels. The turbulent transport of O 3 induced by cloud top radiative cooling is revealed as an important mechanism of vertical transport of O 3 within a cloud topped boundary layer, contributing to the maximum nocturnal surface O 3 , which has great implications for understanding atmospheric O 3 variation.
关键词：cloud top radiative cooling;ozone;turbulent transport
