1. 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

2. Ozone depletion events
Various levels of depletion
(20 to 0.1 ppbv)
In boundary layer

3. Bromine chemistry • Source of bromine? Sea salt / snow
• Recycling through aerosols
• Interaction between BrOx and HOx and BrOx and NOx

4. 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

5. TOPSE data Features • Radicals drop of with lower O3
• BrO maximum at higher O3
• Range of O3 a SBr concentration

6. Box Model

7. Initial comparison Features • Not enough O3 loss • NOx drops too low
• No increase in PAN
• Hydrocarbons seen reasonable

8. 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

9. NO3- + 2Br- + 3H+ -> Br2 + HNO2 + H2O
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 reaction
J. Phys. Chem., 1989,

10. Updated comparison Features • NOx concentration better
• PAN increases but not much (CH3CHO?)
• Hydrocarbon decay good

11. Updated comparison Features • OH concentration seems high
• RO2 concentration good
• Too little BrO?
• Too much SBr?

12. What changes with NOx?
Standard
With bromine

13. What happens to HOx?
Standard
With bromine

14. 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.