Extreme surface ozone episodes over the Arabian Gulf and their relationship with meteorological conditions

Abstract

In this study, we investigated the seasonal distribution of extreme surface ozone (O₃) episodes in association with meteorological conditions over the Arabian Gulf (AG) between 2016 and 2019. We used hourly surface O₃ measurements from the United States Embassy in Manama and air temperature observations from the Iowa Environmental Mesonet. We computed the maximum daily 8-h average of O₃ using the Air Quality Index methodology. The results showed that the air quality in Manama can be categorized as “good,” “moderate,” “unhealthy for sensitive groups,” “unhealthy,” and “very unhealthy” for 45.31 %, 20.61 %, 19.08 %, 11.63 %, and 3.37 % of the time, respectively. The extreme days, defined as days with MDA8-O₃ ≥ 86 ppb, occurred 72.11 % in summer, 15.65 % in fall, 12.24 % in spring. No extremes were recorded in winter. Our analysis of surface O₃ values obtained from the Copernicus Atmosphere Monitoring Service showed that the O₃ levels during summer extremes were higher by 10 ppb than their climatological mean. We then categorized the O₃ summer extremes into single-day episodes (SDEs) and multi-day episodes (MDEs), revealing that most of the extremes (73.58 %) were MDEs. An analysis of meteorological conditions using the fifth-generation atmospheric reanalysis from the European Centre for Medium-Range Weather Forecasts, MODIS-Terra, and the Clouds and the Earth's Radiant Energy System database revealed that the MDEs exhibit increased temperatures, temperature subsidence form the mid-troposphere, weakened wind speeds, low aerosol optical depth, and increased insolation. These conditions are less pronounced during SDEs. Moreover, 5.67 % of the summer extremes were associated with stratospheric intrusions.