Iodine chemistry in the chemistry–climate model SOCOL-AERv2-I

Abstract

Abstract. In this paper, we present a new version of the chemistry–climate model SOCOL-AERv2 supplemented by an iodine chemistry module. We perform three 20-year ensemble experiments to assess the validity of the modeled iodine and to quantify the effects of iodine on ozone. The iodine distributions obtained with SOCOL-AERv2-I agree well with AMAX-DOAS observations and with CAM-chem model simulations. For the present-day atmosphere, the model suggests that the iodine-induced chemistry leads to a 3 %–4 % reduction in the ozone column, which is greatest at high latitudes. The model indicates the strongest influence of iodine in the lower stratosphere with 30 ppbv less ozone at low latitudes and up to 100 ppbv less at high latitudes. In the troposphere, the account of the iodine chemistry reduces the tropospheric ozone concentration by 5 %–10 % depending on geographical location. In the lower troposphere, 75 % of the modeled ozone reduction originates from inorganic sources of iodine, 25 % from organic sources of iodine. At 50 hPa, the results show that the impacts of iodine from both sources are comparable. Finally, we determine the sensitivity of ozone to iodine by applying a 2-fold increase in iodine emissions, as it might be representative for iodine by the end of this century. This reduces the ozone column globally by an additional 1.5 %–2.5 %. Our results demonstrate the sensitivity of atmospheric ozone to iodine chemistry for present and future conditions, but uncertainties remain high due to the paucity of observational data of iodine species.

The historical ozone trends simulated with the SOCOLv4 and their comparison with observations and reanalysis

“…Besides a change in the relative strengths of the lower and upper branches of the BDC there might be additional reasons for the decline in LSO, including: the recent reduction in solar activity (Arsenovic et al, 2018); the influence of halogen-containing very short-lived species and other gases unaccounted for by the MPA (Hossaini et al, 2015;Oman et al, 2016;Oram et al, 2017); increased emissions of inorganic iodine (Cuevas et al, 2018;Karagodin-Doyennel et al, 2021); increased aerosol loading (Andersson et al, 2015); insufficient treatment of diffusion and transport processes in models (Dietmüller et al, 2017(Dietmüller et al, , 2018; unexpected increase in emissions of CFC-11 violating the MPA (Fleming et al, 2020); altitude changes in the extratropical tropopause (Bognar et al, 2022).…”

“…Here, we aim to evaluate ozone trends from 1985-2018 from the ground to the mesosphere using the Earth System Model (ESM) SOCOLv4 (Sukhodolov et al, 2021). To verify if the SOCOLv4 can reproduce the statistically reliable observed ozone trends, we applied DLM to SOCOLv4 simulations, the BASIC composite, and several re-analysis datasets.…”

“…All climate forcings are historical before 2015 and for the years 2015 to 2018 they are switched to the SSP2-4.5 scenario (O'Neill et al, 2016). A detailed description of all modules incorporated into SOCOLv4 as well as more details on the conducted reference experiment can be found in the SOCOLv4 validation paper (Sukhodolov et al, 2021). In this study, the SOCOLv4 runs are in a free-running mode except for QBO which is nudged to observations.…”

The impact of volcanic emission of halogenated compounds on the Southern Hemisphere and Antarctic environment

“…The column amounts of IO are approximately one order of magnitude lower than BrO. The model developed in Karagodin- Doyennel et al (2021) suggests the strongest influence of iodine in the lower stratosphere with an ozone loss of up to 30 ppbv at low latitudes and up to 100 ppbv at high latitudes. Globally averaged, the model suggests iodine-induced chemistry to result in an ozone column reduction of 3-4%, peaking at high latitudes.…”

Theoretical treatment of IO–X (X = N2, CO, CO2, H2O) complexes

“…3,24 The estimation of the contribution of iodine monoxide and its related iodine bearing compounds in the chemical composition of MBL and the stratosphere and in their role in the physical chemical processes occurring there is an active field. Both modelling 25 and experimental 26,27 studies are performed to elucidate, for instance, the role of IO in the tropospheric oxidation of iodine-containing species. These works allowed us to determine the structural, energetic and thermodynamic properties of the reactive and/or non-reactive collisions between IO and the following compounds: Ar, 28 ClO, 29 BrO, 29 CF 3 O, 30 NH 2 , 31 CO, 32,33 H 2 O, 34 IO, 34 OIO, 34 HNO 3 , 35 NO, 36 O 3 , 37 NO 3 , 38 and HO 2 .…”