Constraining the budgets of DMS and Ozone in the remote marine boundary layer
Abstract
Fourteen research flights were conducted in the National Center for Atmospheric Research (NCAR) C-130 near Christmas Island (2°N, 157°W) during August and early September of 2007 as part of the Pacific Atmospheric Sulfur Experiment (PASE). In order to tightly constrain the budgets of ozone and DMS, fluxes were measured at various levels in the marine boundary layer (MBL) from near the surface (30m) to the top of the mixed layer (~500m). The main photochemical agents, HO2, RO2 and OH were also measured. The average O3 concentration in the MBL was ~19 ppbv and exhibited the expected diurnal behavior of buildup at night due to mixing from above followed by photochemical destruction during the daylight hours. Contributions to the budget from O3 photolysis, horizontal advection, vertical turbulent flux divergence and loss to OH, and HO2 were included in the budget. The largest known term is the daytime photolysis to produce OH (average of -0.25 ppb/hour). The magnitude of the horizontal advection term makes a small contribution on average but can be significant on individual flights. The vertical turbulent flux divergence consistently appears as transport from above in conjunction with slow deposition to the ocean surface for a net gain of ~0.08 ppb/hour. The average deposition velocity of ozone to the ocean was observed to be 0.02 cms-1. The average DMS concentration in the MBL was ~70 pptv. Contributions to the budget from chemical reaction, horizontal advection and vertical turbulent flux divergence were included in the study. The budget analysis shows a persistent unexplained sink (~3.5 ppt/hour) during the daytime flights. This missing sink is roughly equal in magnitude to the oxidation by observed OH concentrations, and could be explained by the presence of 1-3 pptv of BrO during the day.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.A51D0133C
- Keywords:
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- 0312 Air/sea constituent fluxes (3339;
- 4504);
- 0322 Constituent sources and sinks