Comment on egusphere-2022-370

Abstract

The tropospheric Ozone Depletion Event (ODE), first observed at Barrow (now known as Utqiagvik), Alaska, is a phenomenon that frequently occurs during the springtime of Arctic. In the present study, we performed a three-dimensional model study on ODEs occurring at Barrow and its surrounding areas between March 28th and April 6th, 2019, using a 3-D multi-scale air quality model, CMAQ. Several ODEs observed at Barrow were successfully captured and two of them were analyzed thoroughly using process analysis. We found that the ODE occurring between March 30th and 31st, 2019 (referred to as ODE1) was caused mainly by a horizontal transport of an ozone-lacking air from the Beaufort sea to Barrow. This ozone-lacking air was formed due to a release of sea-salt aerosols from the Bering Strait under a strong wind condition, resulting from a cyclone generated at the Chukotka Peninsula. It was also found that over the Beaufort sea, the surface ozone drops to a level lower than 5 ppb, and the local chemistry contributed as large as 10 ppb to the ozone loss. Moreover, BrO over the sea was found to attain a maximum of approximately 100 ppt. This ozone-lacking air over the sea was horizontally transported to Barrow, leading to the occurrence of ODE1. Regarding another ODE on April 2nd (ODE2), we found its occurrence also dominated by the horizontal advection from the sea, but under the control of an anti-cyclone. The termination of this ODE was attributed to the replenish of ozone-rich air from the free troposphere by a strong vertical transport.