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SUMMARY: Evaluation of 14CO as a Tracer of OH in a Global Model    - Liam 
 Blyth – Imperial College London
DTSTART:20231121T113000Z
DTEND:20231121T123000Z
UID:TALK206185@talks.cam.ac.uk
CONTACT:Vichawan (Print) Sakulsupich
DESCRIPTION:The Hydroxyl Radical (OH) is one of the most important species
  in atmospheric chemistry due to its role in controlling the lifetime of C
 H4 and several atmospheric pollutants. Due to its high reactivity\, OH has
  a lifetime of ~1 second\, making it challenging to measure. As a result\,
  a proxy species is needed to estimate OH’s temporal and spatial variabi
 lity. Historically this was done using Methyl Chloroform (MCF)\, however\,
  a recent decline in the atmospheric mixing ratio of MCF motivates us to s
 eek an alternative proxy. Here we present the results of global 14CO simul
 ations and investigate its ability to determine the spatial and temporal t
 rends in OH. Simulated 14CO agrees within a few molecules cm-3 with measur
 ements at various locations\, and shows the clear trends seen in measured 
 data. Simulations show local 14CO concentrations have a reliance on hemisp
 heric\, rather than local OH trends\, particularly in the higher latitudes
 \, implying it has the ability to capture trends on this scale. Our result
 s also show that a large-scale measurement campaign at an individual site 
 at mid-latitude (Mace Head) could have detected the 10% increase in OH bur
 den in the NH simulated over the last 35 years in the model. To investigat
 e this\, a new approach is developed to remove the effect of the solar cyc
 le on 14CO concentrations\, allowing long-term trends to be better analyse
 d. Our simulations\, in conjunction with global measurements\, have the po
 tential to solve the recent disparity between OH trends seen in atmospheri
 c models and measurement data.\n\n----------------------------------------
 --------------------\n\n\nCAS UnionRoad is inviting you to a scheduled Zoo
 m meeting.\n\nTopic: CAS seminar: Liam Blyth\nTime: Nov 21\, 2023 11:30 AM
  London\n\nJoin Zoom Meeting\nhttps://us02web.zoom.us/j/89988064036?pwd=SW
 VxNEFqdCtnaSt2Mk5hLzNqQ3FyQT09\n\nMeeting ID: 899 8806 4036\nPasscode: 312
 382\n\n
LOCATION:Chemistry Dept\, Unilever Lecture Theatre and Zoom
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