We document the implementation of the Common Representative Intermediates Mechanism version 2, reduction 5 into the United Kingdom Chemistry and Aerosol model (UKCA) version 10.9. The mechanism is merged with the stratospheric chemistry already used by the StratTrop mechanism, as used in UKCA and the UK Earth System Model, to create a new CRI‐Strat mechanism. CRI‐Strat simulates a more comprehensive treatment of non‐methane volatile organic compounds (NMVOCs) and provides traceability with the Master Chemical Mechanism. In total, CRI‐Strat simulates the chemistry of 233 species competing in 613 reactions (compared to 87 species and 305 reactions in the existing StratTrop mechanism). However, while more than twice as complex than StratTrop, the new mechanism is only 75% more computationally expensive. CRI‐Strat is evaluated against an array of in situ and remote sensing observations and simulations using the StratTrop mechanism in the UKCA model. It is found to increase production of ozone near the surface, leading to higher ozone concentrations compared to surface observations. However, ozone loss is also greater in CRI‐Strat, leading to less ozone away from emission sources and a similar tropospheric ozone burden compared to StratTrop. CRI‐Strat also produces more carbon monoxide than StratTrop, particularly downwind of biogenic VOC emission sources, but has lower burdens of nitrogen oxides as more is converted into reservoir species. The changes to tropospheric ozone and nitrogen budgets are sensitive to the treatment of NMVOC emissions, highlighting the need to reduce uncertainty in these emissions to improve representation of tropospheric chemical composition.

中文翻译：

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英国化学和气溶胶模型的共同代表中介机制版本2

我们记录了通用代表中间体机制第2版的实现，将第5版还原为英国化学和气溶胶模型（UKCA）10.9版。该机制与StratTrop机制已经使用的平流层化学（例如UKCA和UK地球系统模型）合并在一起，创建了一种新的CRI-Strat机制。CRI-Strat模拟非甲烷挥发性有机化合物（NMVOCs）的更全面处理，并通过主化学机理提供可追溯性。总体而言，CRI-Strat模拟了613种竞争中的233种化学反应（相比之下，现有StratTrop机制中的87种和305种反应）。但是，尽管新机制比StratTrop复杂两倍以上，但新机制的计算开销仅高出75％。针对一系列CRI-Strat评估原位UKCA模型中使用StratTrop机制进行的遥感观测和模拟。与地表观测相比，发现增加了地表附近臭氧的产生，导致更高的臭氧浓度。但是，与StratTrop相比，CRI-Strat中的臭氧损失也更大，导致排放源中的臭氧更少，而对流层臭氧负担也相似。CRI-Strat还比StratTrop产生更多的一氧化碳，特别是在生物VOC排放源的顺风处，但是随着更多的氮氧化物转化成储集层物种，氮氧化物的负担降低。对流层臭氧和氮预算的变化对NMVOC排放的处理很敏感，强调需要减少这些排放的不确定性以改善对流层化学成分的表示。