A SIMPLE SCHEME FOR PARTITIONING AIRCRAFT-MEASURED OZONE FLUXES INTO SURFACE-UPTAKE AND CHEMICAL TRANSFORMATION

The interplay between surface uptake and atmospheric chemistry makes a ircraft-measured ozone fluxes near the surface complex to interpret ov er such surfaces as recently, cultivated bare soil, newly cut hay, cit ies and near highways in the San Joaquin Valley of California (the Cal ifornia Ozone Deposition Experiment, 1991). In this study, a simple pa rtitioning scheme is proposed, based on the estimation of the ozone su rface-uptake rate by a regressional fit of ozone flux vs latent heat f lux and a vegetation index, over well-irrigated vegetative surfaces, b y assuming that ozone flux residuals are due to atmospheric chemistry. The contributions to ozone fluxes by atmospheric chemistry over surfa ces other than well-irrigated vegetative surfaces can then be estimate d from the difference between the estimated ozone surface-uptake rate and the measured ozone flux. The estimates indicate that chemical cont ributions are more significant than surface-uptake and that the chemic al contributions are dominated primarily by ozone destruction over rec ently cultivated bare soil, newly cut hay, city and near highway. The dominant sink for ozone destruction is analytically shown to be caused by NO concentrations in excess of the photostationary state,which are believed to be linked to the strong NO emissions from the surfaces.