16 Nov 2022
16 Nov 2022
Status: this preprint is currently under review for the journal ACP.

Large Simulated Future Changes in the Nitrate Radical Under the CMIP6 SSP Scenarios: Implications for Oxidation Chemistry

Scott Archer-Nicholls1,a, Rachel Allen1, Nathan Luke Abraham1,2, Paul Thomas Griffiths1,2, and Alexander Thomas Archibald1,2 Scott Archer-Nicholls et al.
  • 1Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK
  • 2NCAS-Climate, University of Cambridge, Cambridge, CB2 1EW, UK
  • anow at: IT Services, University of Manchester, Manchester, M13 9PL, UK

Abstract. The nitrate radical (NO3) plays an important role in the chemistry of the lower troposphere, acting as the principle oxidant during the night. Previous model simulations suggest that the levels of NO3 have increased dramatically since the pre-industrial. Here, we show projections of the evolution of the NO3 radical from 1850–2100 using the UKESM1 Earth System model under the CMIP6 SSP scenarios. Our model results highlight diverse trajectories for NO3, with some scenarios and regions undergoing rapid growth of NO3 to unprecedented levels over the course of the 21st Century, and others seeing sharp declines. The local increases in NO3 are driven not only by local changes in emissions of nitrogen oxides but have an important climate component, with NO3 being favoured in warmer future climates. The changes in NO3 lead to changes in the oxidation of important secondary organic aerosol precursors, with potential impacts to particulate matter pollution regionally and globally. This work highlights the potential for substantial future growth in NO3 and the need to better understand the formation of SOA from NO3 to accurately predict future air quality and climate implications.

Scott Archer-Nicholls et al.

Status: open (until 28 Dec 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-706', Anonymous Referee #1, 25 Nov 2022 reply

Scott Archer-Nicholls et al.

Scott Archer-Nicholls et al.


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Short summary
The nitrate radical is the major oxidant at nighttime but much less is known about it than the other oxidants ozone and OH. Here we use Earth System model calculations to show how the nitrate radical has changed in abundance from 1850–2014 and through to 2100 under a range of different climate and emission scenarios. We show that depending on the emissions and climate scenario significant increases are projected with implications for the oxidation of VOCs and the formation fine aerosol.