Boundary Layer Ozone Dynamics: Direct Observations over Arctic and Ocean Locations


Influences of anthropogenic emissions from the northern hemisphere mid-latitudes can be seen in remote arctic and oceanic regions previously thought to be removed from the effects of pollution. Direct observations of surface layer ozone have been underrepresented above the hydrosphere and cryosphere. With oceans covering two thirds of the Earth\u27s surface, the air-sea exchange plays an important role in the surface energy budget and in the transfer of ozone to the ocean surface. Recent developments of a fast response ozone instrument have allowed for ozone flux measurements over the open ocean. I investigated the quenching effect due to water vapor on the ozone instrument and quantified the corrections required for accurate measurements. A method for removing water vapor while leaving ozone unchanged was described. Mean water vapor concentrations were reduced by 77% and fast fluctuations of the water vapor signal were reduced by 97%. The transport of ozone over the open ocean was examined at island monitoring stations and from ship-board measurements. It has been speculated that ozone ocean uptake is determined by chemical enhancements. Currently, limited concurrent measurements of ozone flux and ocean surface chemistry have occurred. This work examined the use of satellite derived ocean surface chemistry measurements. In-situ and satellite derived measurements of chlorophyll agreed within 1 μg l-1 when the wind speed was greater than 6 m s-1. The fast response ozone instrument was deployed during a two month long field campaign to study ozone depletion events in Barrow, Alaska. During the campaign, seven ozone depletion events (ODE) where the ozone would drop below 1.0 ppbv were observed. The longest ODE lasted over 72 hours with residual ozone varying between 0.1 to 0.8 ppbv. Ozone surface deposition rates were relatively low, ≤ 0.02-0.05 cm s−1 during most times. There was no clear evidence of ozone in interstitial air being influenced by photochemical processes. Concurrent atmospheric turbulence measurements from seven sonic anemometers showed general agreement except when winds were disturbed by the location of a nearby building. A composite boundary layer height was defined during the campaign, based on atmospheric turbulence measurements and validated against over 100 radiosonde observations. Sustained periods of boundary layer heights below 50 m were seen for several days. There was not a clear correlation between ozone depletion events and boundary layer height

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