Effects of the sea-land breeze on coastal ozone pollution in the Yangtze River Delta, China

Aim at the effects of the coastal characteristic on ozone pollution in the Yangtze River Delta (YRD), a campaign was launched at the Ningbo, China in the summer of 2020, which mainly covered the monitoring of the vertical profiles of ozone (O3) concentration, three-dimensional wind field, temperature and humidity profiles and parameters of boundary layer dynamic-thermodynamic structure. At the coastal research station, a sea-land breeze (SLB) circulation accompanied by a concurrent coastal low-level jets (CLLJ) structure was observed and identified during 11-12 May 2020. The sea breeze first formed at 10:00 LT on 11 May, turned to land breeze at night, and returned to sea breeze again at 10:00 LT the next morning, prevailing at altitudes of 0-0.5 km and 0-0.3 km respectively. Land breeze at night carries O-3 from the inland to the sea forming high ozone levels over the sea, and the shift of the sea breeze during daytime further blew pollution back to the land. Additionally, the conversion of SLB contributed to the occurrence of CLLJ at the altitudes of similar to 0.3-0.7 km by 02:00 and 06:00 LT, of which the center of wind speed reached similar to 13 m s(-1). The CLLJ-induced turbulent activity decoupled the residual layer (RL) and stable boundary layer, leading to a reduction of RL-O-3 levels and an increase of similar to 50 mu g m(-3) in surface-O-3 concentration. The YRD's unique coastal characteristics make O-3 pollution causes in coastal areas more complicated. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study focused on the impact of coastal characteristics on ozone pollution in the Yangtze River Delta, revealing the complexity of ozone pollution causes in coastal areas, with sea-land breeze circulation and coastal low-level jets playing a significant role in coastal ozone concentration variations.