Loading...
Oxidation processes in the eastern Mediterranean atmosphere: evidence from the modelling of HOx measurements over Cyprus
Mallik, Chinmay Tomsche, Laura Bourtsoukidis, Efstratios Crowley, John N. Derstroff, Bettina Fischer, Horst Hafermann, Sascha Hueser, Imke Javed, Umar Kessel, Stephan
Mallik, Chinmay
Tomsche, Laura
Bourtsoukidis, Efstratios
Crowley, John N.
Derstroff, Bettina
Fischer, Horst
Hafermann, Sascha
Hueser, Imke
Javed, Umar
Kessel, Stephan
Advisors
Editors
Other Contributors
EPub Date
Publication Date
2018-07-31
Submitted Date
Collections
Files
Loading...
main article
Adobe PDF, 6.8 MB
Other Titles
Abstract
The Mediterranean is a climatically sensitive region located at the crossroads of air masses from three continents: Europe, Africa, and Asia. The chemical processing of air masses over this region has implications not only for the air quality but also for the long-range transport of air pollution. To obtain a comprehensive understanding of oxidation processes over the Mediterranean, atmospheric concentrations of the hydroxyl radical (OH) and the hydroperoxyl radical (HO2) were measured during an intensive field campaign (CYprus PHotochemistry EXperiment, CYPHEX-2014) in the northwest of Cyprus in the summer of 2014. Very low local anthropogenic and biogenic emissions around the measurement location provided a vantage point to study the contrasts in atmospheric oxidation pathways under highly processed marine air masses and those influenced by relatively fresh emissions from mainland Europe.
The CYPHEX measurements were used to evaluate OH and HO2 simulations using a photochemical box model (CAABA/MECCA) constrained with CYPHEX observations of O3, CO, NOx, hydrocarbons, peroxides, and other major HOx (OH+HO2) sources and sinks in a low-NOx environment (<100pptv of NO). The model simulations for OH agreed to within 10% with in situ OH observations. Model simulations for HO2 agreed to within 17% of the in situ observations. However, the model strongly under-predicted HO2 at high terpene concentrations, this under-prediction reaching up to 38% at the highest terpene levels. Different schemes to improve the agreement between observed and modelled HO2, including changing the rate coefficients for the reactions of terpene-generated peroxy radicals (RO2) with NO and HO2 as well as the autoxidation of terpene-generated RO2 species, are explored in this work. The main source of OH in Cyprus was its primary production from O3 photolysis during the day and HONO photolysis during early morning. Recycling contributed about one-third of the total OH production, and the maximum recycling efficiency was about 0.7. CO, which was the largest OH sink, was also the largest HO2 source. The lowest HOx production and losses occurred when the air masses had higher residence time over the oceans.
Citation
Mallik, C., Tomsche, L., Bourtsoukidis, E., Crowley, J. N., Derstroff, B., Fischer, H., Hafermann, S., Hüser, I., Javed, U., Keßel, S., Lelieveld, J., Martinez, M., Meusel, H., Novelli, A., Phillips, G. J., Pozzer, A., Reiffs, A., Sander, R., Taraborrelli, D., Sauvage, C., Schuladen, J., Su, H., Williams, J. & Harder, H. (2018). Oxidation processes in the eastern Mediterranean atmosphere: evidence from the modelling of HOx measurements over Cyprus. Atmospheric Chemistry and Physics, 18(14), 10825-10847.
Publisher
Copernicus Publications
Journal
Atmospheric Chemistry and Physics
Research Unit
DOI
10.5194/acp-18-10825-2018
PubMed ID
PubMed Central ID
Type
Article
Language
en
Description
Series/Report no.
ISSN
1680-7316
EISSN
1680-7324