English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

. We present the first incorporation of the Common RepresentativeIntermediates version 2.2 tropospheric chemistry mechanism, CRI v2.2,combined with stratospheric chemistry, into the global chemistry–climateUnited Kingdom Chemistry and Aerosols (UKCA) model to give the CRI-Strat 2mechanism. A rigorous comparison of CRI-Strat 2 with the earlier version,CRI-Strat, is performed in UKCA in addition to an evaluation of threemechanisms, CRI-Strat 2, CRI-Strat and the standard UKCA chemical mechanism,StratTrop v1.0, against a wide array of surface and airborne chemical data. CRI-Strat 2 comprises a state-of-the-art isoprene scheme, optimized againstthe Master Chemical Mechanism v3.3.1, which includes isoprene peroxy radical isomerization,HOx recycling through the addition of photolabile hydroperoxy aldehydes(HPALDs), and isoprene epoxy diol (IEPOX) formation. CRI-Strat 2 also features updates to severalrate constants for the inorganic chemistry, including the reactions ofinorganic nitrogen and O(1D). The update to the isoprene chemistry in CRI-Strat 2 increases OH over thelowest 500 m in tropical forested regions by 30 %–50 % relative toCRI-Strat, leading to an improvement in model–observation comparisons forsurface OH and isoprene relative to CRI-Strat and StratTrop. Enhancedoxidants also cause a 25 % reduction in isoprene burden and an increase inoxidation fluxes of isoprene and other biogenic volatile organic compounds(BVOCs) at low altitudes with likely impacts on subsequent aerosol formation, atmosphericlifetime, and climate. By contrast, updates to the rate constants of O(1D) with its mainreactants relative to CRI-Strat reduces OH in much of the free troposphere,producing a 2 % increase in the methane lifetime, and increases thetropospheric ozone burden by 8 %, primarily from reduced loss viaO(1D)+H2O. The changes to inorganic nitrogen reaction rateconstants increase the NOx burden by 4 % and shift the distributionof nitrated species closer to that simulated by StratTrop. CRI-Strat 2 is suitable for multi-decadal model integrations and theimproved representation of isoprene chemistry provides an opportunity toexplore the consequences of HOx recycling in the United Kingdom EarthSystem Model (UKESM1). This new mechanism will enable a re-evaluation of theimpact of BVOCs on the chemical composition of the atmosphere and further probethe feedback between the biosphere and the climate.

Improvements to the representation of BVOC chemistry–climate interactions in UKCA (v11.5) with the CRI-Strat 2 mechanism: incorporation and evaluation