Abstract
Abstract. To mitigate the human impact on climate change, it is essential to determine the contribution of emissions to the concentration of trace gases. In particular, the source attribution of short-lived species such as OH and HO2 is important as they play a crucial role for atmospheric chemistry. This study presents an advanced version of a tagging method for OH and HO2 (HOx) which attributes HOx concentrations to emissions. While the former version (V1.0) only considered 12 reactions in the troposphere, the new version (V1.1), presented here, takes 19 reactions in the troposphere into account. For the first time, the main chemical reactions for the HOx chemistry in the stratosphere are also regarded (in total 27 reactions). To fully take into account the main HO2 source by the reaction of H and O2, the tagging of the H radical is introduced. In order to ensure the steady-state assumption, we introduce rest terms which balance the deviation of HOx production and loss. This closes the budget between the sum of all contributions and the total concentration. The contributions to OH and HO2 obtained by the advanced tagging method V1.1 deviate from V1.0 in certain source categories. For OH, major changes are found in the categories biomass burning, biogenic emissions and methane decomposition. For HO2, the contributions differ strongly in the categories biogenic emissions and methane decomposition. As HOx reacts with ozone (O3), carbon monoxide (CO), reactive nitrogen compounds (NOy), non-methane hydrocarbons (NMHCs) and peroxyacyl nitrates (PAN), the contributions to these species are also modified by the advanced HOx tagging method V1.1. The contributions to NOy, NMHC and PAN show only little change, whereas O3 from biogenic emissions and methane decomposition increases in the tropical troposphere. Variations for CO from biogenic emissions and biomass burning are only found in the Southern Hemisphere.
Highlights
The radicals hydroxyl (OH) and hydroperoxyl (HO2) are crucial for atmospheric chemistry
The TAGGING submodel is coupled to the detailed chemical solver MECCA from which it obtains information about tracer concentrations and reaction rates. It calculates the contributions of source categories to O3, carbon monoxide (CO), NOy, peroxyacyl nitrates (PAN) and non-methane hydrocarbons (NMHCs) concentrations
The tagging method V1.0 described by Grewe et al (2017) determines the contribution of source categories to O3, NOy, CO, NMHC, PAN, OH and HO2 concentrations
Summary
The radicals hydroxyl (OH) and hydroperoxyl (HO2) are crucial for atmospheric chemistry. We present a revised version V1.1 of the HOx tagging method, largely improving these shortcomings It includes the main chemical reactions of HOx chemistry in the troposphere and stratosphere. EMAC is a numerical chemistry and climate simulation system that includes submodels describing tropospheric and middle atmosphere processes and their interaction with oceans, land and human influences (Jöckel et al, 2010) It uses the second version of the Modular Earth Submodel System (MESSy2.53) to link multi-institutional computer codes. The TAGGING submodel (as described by Grewe et al, 2017) is coupled to the detailed chemical solver MECCA from which it obtains information about tracer concentrations and reaction rates Based on this information, it calculates the contributions of source categories to O3, CO, NOy, PAN and NMHC concentrations. The implementation is based on MESSy2.53 and will be available in MESSy2.54
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