Description and evaluation of the UKCA stratosphere-troposphere chemistry scheme (StratTrop vn 1.0) implemented in UKESM1



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Ordóñez García, Carlos (2020) Description and evaluation of the UKCA stratosphere-troposphere chemistry scheme (StratTrop vn 1.0) implemented in UKESM1. Geoscientific model development, 13 (3). pp. 1223-1266. ISSN 1991-959X

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Here we present a description of the UKCA StratTrop chemical mechanism, which is used in the UKESM1 Earth system model for CMIP6. The StratTrop chemical mechanism is a merger of previously well-evaluated tropospheric and stratospheric mechanisms, and we provide results from a series of bespoke integrations to assess the overall performance of the model.
We find that the StratTrop scheme performs well when compared to a wide array of observations. The analysis we present here focuses on key components of atmospheric composition, namely the performance of the model to simulate ozone in the stratosphere and troposphere and constituents that are important for ozone in these regions. We find that the results obtained for tropospheric ozone and its budget terms from the use of the StratTrop mechanism are sensitive to the host model; simulations with the same chemical mechanism run in an earlier version of the MetUM host model show a range of sensitivity to emissions that the current model does not fall within.
Whilst the general model performance is suitable for use in the UKESM1 CMIP6 integrations, we note some shortcomings in the scheme that future targeted studies will address.

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© Author(s) 2020. Artículo firmado por 28 autores. The authors would like to acknowledge the international community of UKCA users for all their efforts in developing and applying the model. In particular, we would like to acknowledge Prof. John A. Pyle, who pioneered the development of the UKCA project. We would especially like to thank the atmospheric chemistry observational community, who have developed numerous datasets used in this paper to help evaluate the model. This work used JASMIN, the UK collaborative data analysis facility. We would like to thank Bodeker Scientific for providing the combined NIWA–BS total column ozone database. We thank the Global Emission Initiative (GEIA) for providing access to emissions data via the Emissions of atmospheric Compounds and Compilation of Ancillary Data (ECCAD) archive. The development of UKCA for inclusion in UKESM1 was facilitated by the use of the Monsoon2/NEXCS system, a collaborative facility supplied under the Joint Weather and Climate Research Programme, a strategic partnership between the Met Office and the Natural Environment Research Council. This research has been supported by the NERC–Met Office Joint Weather and Climate Research Programme (UKCA); NERC (grant nos. NCAS, NCEO, NE/K001272/1, NE/M00273X/1, NE/P016383/1); the BEIS/Defra Met Office Hadley Centre Climate Programme (grant no. GA01101) and the UK–China Research and Innovation Partnership Fund through CSSP China, part of the Newton Fund; the Horizon 2020 Framework Programme (CRESCENDO, grant no. 779366); FP7 (project StratoClim, grant no. 603557); the Spanish Ministerio de Economía y Competitividad (RYC-2014-15036) and the New Zealand Government under its Strategic Science Investment Fund (Deep South National Science Challenge).

Uncontrolled Keywords:Environment simulator jules; Organic-compound emissions; General-circulation model; Biomass burning emissions; Climate-composition model; Chemical-transport model; Ozone dry deposition; Atmospheric chemistry; Isoprene emission; Global-scale
Subjects:Sciences > Physics > Atmospheric physics
ID Code:63909
Deposited On:16 Feb 2021 10:28
Last Modified:16 Feb 2021 11:15

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