Ozone Dry Deposition Velocities for Coastal Waters

Abstract

Air-sea exchange rates for ozone were measured by the eddy correlation technique at a site on the north Norfolk coast in the UK. The average surface resistance to ozone uptake was found to be, rs(O3) = 1,000 ± 100 s m-1. Micrometeorological measurements of trace gas fluxes to ocean surfaces are rare but a review of available measurements suggests that we can constrain sea water surface resistance for ozone to between 1,000 (Regener (1974), and this work) and 1,890 s m-1 (Lenschow et al., 1982), yielding surface deposition velocities between 0.53 and 1.0 mm s-1. These values are more than an order of magnitude greater than can be explained by laboratory determined mass accommodation coefficients for ozone to water. The importance of dry deposition with respect to process air-sea exchange models is highlighted. A trend in surface deposition velocity with wind speed was also observed supporting a surface chemical enhancement mechanism of ozone uptake which in turn is enhanced by near surface mixing processes.