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Modeling the chemistry during TOPSE low ozone events. Modeling the chemistry during TOPSE low ozone events. Mathew Evans, D. Jacob,. Mathew Evans, D. Jacobs, C. Cantrell, F. Eisele, F. Flocke, A. Fried, B. Ridley, B Heikes, D Blake, R Talbot + many other from TOPSE and Harvard. - PowerPoint PPT Presentation
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Modeling the chemistry during TOPSE low ozone events
Mathew Evans, D. Jacob,
Modeling the chemistry
during TOPSE low ozone
events
Mathew Evans, D. Jacobs, C. Cantrell, F. Eisele, F. Flocke, A. Fried, B. Ridley, B Heikes, D Blake, R Talbot + many other from TOPSE and [email protected]
Ozone depletion events
• Various levels of depletion(20 to 0.1 ppbv)
• In boundary layer
Bromine chemistry
• Source of bromine? Sea salt / snow
• Recycling through aerosols
• Interaction between BrOx and HOx and BrOx and NOx
TOPSE data
Features
• NOx minimum at 10 ppbv of O3
• PAN increases with lower O3
• Hydrocarbons drop with O3, ethyne linearly, ethane curved
North of 55N, Below 500m, 11-13 hr local
TOPSE data
Features
• Radicals drop of with lower O3
• BrO maximum at higher O3
• Range of O3 a SBr concentration
Box Model
Initial comparison
Features
• Not enough O3 loss
• NOx drops too low
• No increase in PAN
• Hydrocarbons seen reasonable
Initial comparison
Features
• Radicals concentrations seem reasonable
• BrO concentrations seem reasonable
• Model seems to have less efficient O3 loss, or some loss of Br from system
Problems? Solution?
• Not enough O3 destruction
• Too much NOx loss
• Solution?
NO3- + 2Br- + 3H+ Br2 + HNO2 + H2O
Lengyel, Nagy, Bazsa,Kinetic study of the autocatalytic nitric acid - bromide reaction
and its reverse the nitrous acid-bromine reactionJ. Phys. Chem., 1989, 2801-2807
Updated comparison
Features
• NOx concentration better
• PAN increases but not much (CH3CHO?)
• Hydrocarbon decay good
Updated comparison
Features
• OH concentration seems high
• RO2 concentration good
• Too little BrO?
• Too much SBr?
What changes with NOx?
Standard With bromine
What happens to HOx?
Standard With bromine
Conclusions
• Simple model reproduces features of the TOPSE data
• Agreement improves with extra reaction to convert NO3
- to NOx.
• Model seems to underestimate efficiency of O3 loss with respect to SBr.
• PAN chemistry may relate to CH3CHO from snow pack.