Abstract
In January 2017, historic forest fires occurred in south-central Chile. Although their causes and consequences on health and ecosystems were studied, little is known about their atmospheric effects. Based on chemistry-transport modeling with WRF-CHIMERE, the impact of the 2017 Chilean mega-fires on regional atmospheric composition, and the associated meteorological feedback, are investigated. Fire emissions are found to increase pollutants surface concentration in the capital city, Santiago, by +150% (+30 µg/m3) for PM2.5 and +50% (+200 ppb) for CO on average during the event. Satellite observations show an intense plume extending over 2000 km, well reproduced by the simulations, with Aerosol Optical Depth at 550 nm as high as 4 on average during the days of fire activity, as well as dense columns of CO and O3. In addition to affecting atmospheric composition, meteorology is also modified through aerosol direct and indirect effects, with a decrease in surface radiation by up to 100 W/m2 on average, leading to reductions in surface temperatures by 1 K and mixing layer heights over land by 100 m, and a significant increase in cloud optical depth along the plume. Large deposition fluxes of pollutants over land, the Pacific ocean and the Andes cordillera are found, signaling potential damages to remote ecosystems.
Highlights
In summertime, air quality in central Chile (32◦ –38◦ S, 70◦ –73◦ W) is mostly affected by ozone (O3 ) pollution in urban and sub-urban areas, with hourly maxima reaching typically up to 55 ppb in downtown Santiago [1]
In the fire case, simulated concentrations are much closer to observations, especially for PM2.5 and Carbon monoxide (CO) the spread is larger in the simulation
This study investigated the impacts on air quality and meteorology of the early
Summary
Air quality in central Chile (32◦ –38◦ S, 70◦ –73◦ W) is mostly affected by ozone (O3 ) pollution in urban and sub-urban areas, with hourly maxima reaching typically up to 55 ppb in downtown Santiago [1]. This phenomenon originates in the combination of large emissions of nitrogen oxides (NOx ) from traffic and industry Santiago), with increased photo-chemistry [1,2] The latter is made possible by long days and intense solar radiation. The production and transport of O3 by these events exacerbate air pollution in the affected urban areas [4]
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