Abstract
Abstract. This paper features the new atmosphere–ocean–aerosol–chemistry–climate model, SOlar Climate Ozone Links (SOCOL) v4.0, and its validation. The new model was built by interactively coupling the Max Planck Institute Earth System Model version 1.2 (MPI-ESM1.2) (T63, L47) with the chemistry (99 species) and size-resolving (40 bins) sulfate aerosol microphysics modules from the aerosol–chemistry–climate model, SOCOL-AERv2. We evaluate its performance against reanalysis products and observations of atmospheric circulation, temperature, and trace gas distribution, with a focus on stratospheric processes. We show that SOCOLv4.0 captures the low- and midlatitude stratospheric ozone well in terms of the climatological state, variability and evolution. The model provides an accurate representation of climate change, showing a global surface warming trend consistent with observations as well as realistic cooling in the stratosphere caused by greenhouse gas emissions, although, as in previous model versions, a too-fast residual circulation and exaggerated mixing in the surf zone are still present. The stratospheric sulfur budget for moderate volcanic activity is well represented by the model, albeit with slightly underestimated aerosol lifetime after major eruptions. The presence of the interactive ocean and a successful representation of recent climate and ozone layer trends make SOCOLv4.0 ideal for studies devoted to future ozone evolution and effects of greenhouse gases and ozone-destroying substances, as well as the evaluation of potential solar geoengineering measures through sulfur injections. Potential further model improvements could be to increase the vertical resolution, which is expected to allow better meridional transport in the stratosphere, as well as to update the photolysis calculation module and budget of mesospheric odd nitrogen. In summary, this paper demonstrates that SOCOLv4.0 is well suited for applications related to the stratospheric ozone and sulfate aerosol evolution, including its participation in ongoing and future model intercomparison projects.
Highlights
Global modeling of the atmosphere and its interaction with oceans, cryosphere, biosphere, and land surface dates back several decades (e.g., Manabe and Bryan, 1969)
In terms of differences to the earlier versions, we only focus on those between the atmospheric part of the latest version, ECHAM6, and the atmospheric part used in SOCOLv3, ECHAM5.4, as changes between versions contribute the differences between the chemical response of SOCOLv4 and all subversions of SOCOLv3
This paper presents the fourth generation of the coupled chemistry–climate model SOlar Climate Ozone Links (SOCOL)
Summary
Global modeling of the atmosphere and its interaction with oceans, cryosphere, biosphere, and land surface dates back several decades (e.g., Manabe and Bryan, 1969). Other issues and research fields include the appearance of an unprecedentedly large ozone hole over the Northern Hemisphere in spring 2020 (Witze, 2020; Manney et al, 2020); the formation of a large and deep Antarctic ozone hole in autumn 2020 (NASA Ozone Watch, https: //ozonewatch.gsfc.nasa.gov/, last access: 2 September 2021); continuous unexpected chlorofluorocarbon (CFC)-11 emissions (Fleming et al, 2020); a potential decline of the solar activity (Arsenovic et al, 2018); the potential stratospheric injection of sulfur-containing species for solar geoengineering purposes (Tilmes et al, 2009; Vattioni et al, 2019); and a potential impact of increasing trends of iodine in the stratosphere (Koenig et al, 2020) These examples underline that our understanding of atmospheric ozone and atmospheric chemistry in general, is far from being fully resolved and inspires further model developments and studies of the ozone layer evolution, in the present and future. The validation is split into two main parts: atmospheric dynamics (Sect. 3.2) and atmospheric chemistry with the primary focus on stratospheric ozone (Sect. 3.3)
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