Comparison of scientific findings from major ozone field studies in North America and Europe

During the past decade, nearly 600 million dollars were invested in more th an 30 major held studies in North America and Europe examining tropospheric ozone chemistry, meteorology, precursor emissions, and modeling. Most of t hese studies were undertaken to provide new or refined knowledge about ozon e accumulation and to assist in the development of economical and effective emissions management practices for ozone. In this paper, we describe a sel ection of field research programs conducted under a wide range of geographi cal and climatological conditions in North America and Europe. The designs of these studies were generally similar, employing a combination of ground- based observation networks, upper-air sampling, and meteorological observat ions. Analysis and interpretation of the resulting data were combined with improved inventories of ozone precursor emissions and air quality modeling to develop new or enhanced knowledge about photochemical processes under va rious tropospheric conditions. The scientific results from these studies co ntained few surprises; in fact, they generally affirmed the conclusions in the review by the US National Research Council (NRC, 1999). Key findings in clude: (1) reaffirmation that tropospheric ozone is a multi-scale phenomeno n extending to continental boundaries; (2) aerometric conditions aloft are important to ground-level ozone; (3) biogenic sources make important contri butions to VOC and NOx emissions in parts of eastern North America and sout hern Europe; (4) emissions estimates are among the more uncertain component s of predictive models for ozone; (5) recirculating flow over complex terra in and large water bodies are universally important factors affecting accum ulation of ozone at the ground; (6) nonlinearities in ozone response to pre cursor changes create important degrees of freedom in management strategies - VOC and NOx sensitivities vary extensively in urban and rural areas, mak ing decisions about emissions management complicated; (7) measurement metho ds for many precursors, intermediates, and products of photochemical reacti ons have improved greatly; and (8) additional analysis and interpretation o f existing data from many of these field studies should pay handsome divide nds at relatively modest cost. Published by Elsevier Science Ltd.