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Grid-type flight patterns at an altitude of 30 m were executed in the summer of 1991 by the Canadian Twin Otter flux research aircraft over a 15 km x 16.5 km agricultural area, as part of the San Joaquin Valley Air Quality Study/California Ozone Deposition Experiment (SJVAQS/CODE). Fast-response on board sensors for turbulence, temperature and gas concentrations permitted the spatial mapping of fluxes of momentum, sensible heat, moisture, CO$ sb2$ and ozone. Flux maps were produced in the form of GIS-interpolated 1 km averages, and in the discrete form of those coherent structures of the turbulent process, intermittent in time and space, which dominate the exchange of scalars between the ground and the atmosphere. The magnitude of surface-related mesoscale contributions to the flux was also quantified. Flux observations were compared against radiometrically observed surface temperatures and vegetation indices (NDVI), observed from aircraft and satellite (NOAA AVHRR), and surface characteristics from ground surveys. / Flux maps showed the expected correspondence between greenness, evapo(trans)ration (ET) and CO$ sb2$ exchange. Discrepancies between ozone flux maps and maps of greenness, ET or CO$ sb2$ were more pronounced than would be consistent with the hypothesis of stomatal control of ozone uptake. More insight into control mechanisms on ozone exchange is gained by an examination of the spatial coincidence between transporting structures for the various scalars (heat, moisture, CO$ sb2$ and ozone), through the Jaccard coefficient of co-location (J), which showed a lower value ($ rm0.3<J<0.6$) for coincidence in transfer between ozone and moisture than between moisture and CO$ sb2$ ($ rm0.5<J<0.8$). Analysis of J over the various land-use and crop-types in the test area, opens a door to a more differentiated understanding of the physical and physiological driving forces behind ozone uptake by soil and vegetation.

No description available.