Modelling the impacts of iodine chemistry on the northern Indian Ocean marine boundary layer
Mahajan, Anoop S. (Indian Institute of Tropical Meteorology)
Li, Qinyi (Instituto de Química Física "Rocasolano")
Inamdar, Swaleha (Indian Institute of Tropical Meteorology)
Ram, Kirpa (Banaras Hindu University)
Badia, Alba (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)
Saiz-Lopez, Alfonso (Instituto de Química Física "Rocasolano")

Data:	2021
Resum:	Recent observations have shown the ubiquitous presence of iodine oxide (IO) in the Indian Ocean marine boundary layer (MBL). In this study, we use the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem version 3. 7. 1), including halogen (Br, Cl, and I) sources and chemistry, to quantify the impacts of the observed levels of iodine on the chemical composition of the MBL. The model results show that emissions of inorganic iodine species resulting from the deposition of ozone (span classCombining double low line"inline-formula"O3/span) on the sea surface are needed to reproduce the observed levels of IO, although the current parameterizations overestimate the atmospheric concentrations. After reducing the inorganic emissions by 40 %, a reasonable match with cruise-based observations is found, with the model predicting values between 0. 1 and 1. 2 span classCombining double low line"inline-formula"pptv/span across the model domain MBL. A strong seasonal variation is also observed, with lower iodine concentrations predicted during the monsoon period, when clean oceanic air advects towards the Indian subcontinent, and higher iodine concentrations predicted during the winter period, when polluted air from the Indian subcontinent increases the ozone concentrations in the remote MBL. The results show that significant changes are caused by the inclusion of iodine chemistry, with iodine-catalysed reactions leading to regional changes of up to 25 % in span classCombining double low line"inline-formula"O3/span, 50 % in nitrogen oxides (NO and span classCombining double low line"inline-formula"NO2/span), 15 % in hydroxyl radicals (OH), 25 % in hydroperoxyl radicals (span classCombining double low line"inline-formula"HO2/span), and up to a 50 % change in the nitrate radical (span classCombining double low line"inline-formula"NO3/span), with lower mean values across the domain. Most of the large relative changes are observed in the open-ocean MBL, although iodine chemistry also affects the chemical composition in the coastal environment and over the Indian subcontinent. These results show the importance of including iodine chemistry in modelling the atmosphere in this region.
Ajuts:	European Commission 726349
Nota:	Unidad de excelencia María de Maeztu CEX2019-000940-M
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	SDG 14 - Life Below Water
Publicat a:	Atmospheric chemistry and physics, Vol. 21, Issue 11 (June 2021) , p. 8437-8454, ISSN 1680-7324

DOI: 10.5194/acp-21-8437-2021

18 p, 18.2 MB

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