Abstract
Ozone pollution has been prevalent in the El Paso-Juárez Airshed (EPJA), especially in the past few decades, and it has been on the rise recently. The spatial and temporal distribution of the tropospheric ozone and several key meteorological factors that influence its concentration has not been adequately understood. Therefore, this investigation comprehensively examined 57 high and 48 low ozone episodes occurring in this region during 2013–2019. We found that the interannual ozone concentration in EPJA was strongly affected by anthropogenic emissions. On the other hand, seasonal ozone variations are due to meteorological variables (among them, solar radiation, planetary boundary layer, and winds) in addition to biogenic emission factors. High ozone events are characterized by calm winds, shallow planetary boundary layer (PBL), whereas low ozone events were marked with strong winds, precipitation, and deep PBL. Synoptic and mesoscale wind patterns for these ozone episodes were identified and characterized. Most of the high ozone episodes occurred when an anticyclonic circulation aloft was associated with a 500-mile middle and upper tropospheric high-pressure region over the EPJA. During these events, stable air masses with convective available potential energies (CAPE) values of less than 450 J/kg were found. The importance of surface topography is illustrated by the fact that stations close to the Rio Grande River show a bimodal distribution of wind direction according to the valley axis. High ozone episodes occur with a surface easterly wind that is decoupled from winds above the Franklin mountains.
Highlights
Introduction published maps and institutional affilTropospheric ozone (O3 ) is one of the most significant photooxidants formed by sunlight-driven photochemical reactions of nitrogen oxides (NOx ) and volatile organic compounds (VOCs) [1,2]
We present the probable mechanisms of severe pollution events in this region from synoptic conditions, local circulations, emission concentrations, and planetary boundary layer (PBL) structure
This study presents a new understanding of the spatial and temporal distribution of O3 episodes events in El Paso-Juárez airshed (EPJA)
Summary
Introduction published maps and institutional affilTropospheric ozone (O3 ) is one of the most significant photooxidants formed by sunlight-driven photochemical reactions of nitrogen oxides (NOx ) and volatile organic compounds (VOCs) [1,2]. Ozone plays a central role in atmospheric chemistry, and more generally, the O3 distribution and concentration strongly impact atmospheric temperature. The impacts of O3 on human health and plant growth due to chronic and acute exposure are well documented [3,4,5]. Other studies have shown the adverse health effects of traffic-related air pollutants, including increases in emergency room visits and hospital admissions [6,7]. The neighboring cities, El Paso, Texas, United States and Juárez, Chihuahua, Mexico, share a common airshed, the El Paso-Juárez airshed (EPJA), that frequently has high O3 concentration levels like many major global cities. Every year from May to September (O3 season), the EPJA experiences high O3 events.
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