1. Observations of BrO and (HOBr+Br 2 ) by GT-CIMS during CONTRAST 2014 Dexian Chen, Greg Huey, David Tanner GaTech Andrew Weinheimer, Denise Montzka, Teresa Campos, L. Kaser NCAR Teresa Campos, Mike Reeves Meghan Stell, Janine Aquino, and Frank Flocke NCAR Eric Apel, Rebecca Hornbrook, Alan Hills NCAR Daniel Riemer U Miami Nicola Blake UC Irvine Elliot Atlas, Sue Schauffler, Valeria Donets, R. Lube U Miami and CONTRAST team

2. CIMS Chemical Ionization Mass Spectrometer Measurements:  BrO+I -  BrO·I - (m/z=222, 224)  HOBr+I -  HOBr·I - (m/z=223, 225)  Br 2 +I -  Br 2 ·I - (m/z=285, 287, 289) (HOBr  Br 2, report the sum of HOBr+Br 2 ) Flow Tube (reactor) Mass Spec. inlet

3. CIMS Chemical Ionization Mass Spectrometer Calibrations: Online: periodically flowed cal gas (Br 2, Cl 2 ) into the CIMS Offline: compared sensitivities of BrO, HOBr to sensitivities of the cal gas (in the lab) Flow Tube (reactor) Mass Spec. inlet Cal Gas

4. Measurement Issues During the field campaign we became concerned that Br 2 calibration gas could contaminate inlet walls. i.e. Br 2  BrO Problem alleviated by switching to Cl 2 calibration gas at RF09. For now only reporting data for RF09-RF16 Very high O 3 levels may also lead to BrO artifact during RF15. Needs work but more importantly comparison to DOAS data.

5. Most of the time… Levels of BrO and HOBr+Br 2 near the limits of detection (LOD) LOD for BrO, 0.3-1.5 ppt LOD of HOBr+Br 2, 0.5-2 ppt e.g., RF12 (2/16-2/17)

6. RF10(2/8)  Flight Goal Sample a large pollution plume GUAM

7. RF10 (2/8)

8. RF11 (02/12-0213)  Flight Goal Sample the O 3 layer south of Guam Sample convective outflow GUAM

9. RF11 (02/12-0213)

10. RF15 (2/24-2/25)  Flight Goal Transect to Japan GUAM Spike in BrO w/o increase in HOBr?

11. RF15(02/24)

12. Summary  Most of the time no significant levels of BrO and (HOBr+Br 2 ) were observed  There were a limited number of enhanced layers of BrO and HOBr. They correspond to either stratospheric air or tropospheric air impacted by biomass/pollution.

13. Ongoing work…  Comparisons needed with DOAS to confirm elevated BrO levels and to investigate possible high ozone issue. RF15, RF11, RF10, and transit are high priorities.  Compare stratospheric BrO/HOBr to model calculations.  Investigate origins of high tropospheric signals

14. Transit (2/28-3/1)  GOAL OF FLIGHT Transit(Honolulu- Boulder)

15. Transit flight(02/28-03/01) O3: Weinheimer et al Water vapor: GV platform

16. CIMS Chemical Ionization Mass Spectrometry  backgrounding  Three way valve (periodical measurements mode and background mode) Flow Tube (reactor) Mass Spect inlet Charcoal filter

17.  Offline calibrations in the Lab (BrO) Br 2 +O 3  2BrO (Liao et al., 2011) CIMS Br 2 CIMS Br 2 +O 3 350⁰C

18.  Offline calibrations in the Lab(HOBr) HOBr+NaBr(het)  Br 2 (Liao et al., 2011) CIMS HOBr soln. NaBr salt bed N2N2 HOBr(g)

19.  Limit of Detection (LOD) X