Variations in ozone exposure in the landscape with consideration of topography and coastal climate Klingberg, J. (1), Karlsson, P. E. (2), Pihl Karlsson, G. (2), Hu, Y. (3), Chen, D. (3), Pleijel, H. (1) (1) Department of Plant and Environmental Sciences, University of Gothenburg, P.O. Box 461, SE Gothenburg, Sweden (2) IVL Swedish Environmental Research Institute, P.O. Box 5302, SE Gothenburg, Sweden (3) Department of Earth Sciences, University of Gothenburg, P.O. Box 460, SE Gothenburg, Sweden An activity of the CLEO Programme, funded by the Swedish Environmental Protection Agency. Measurements were funded by the County Administration Board of Västra Götaland.

11 1 Surface ozone concentrations, [O 3 ], depended on the position in the landscape and vary on small geographical scales. Variations in [O 3 ] were related to the distance from the coast and for inland sites to the relative topography within a 3 km radius. Relative topography was more relevant than altitude in explaining the diurnal dynamics of [O 3 ] for inland sites. Diurnal [O 3 ] range correlated with diurnal air temperature range across all sites. Diurnal air temperature range correlated with daily air pressure Climate change may alter surface [O 3 ] through changes in vertical air mixing, independently of changes in emissions, chemistry, deposition or long-range transport Highlights

22 2 Hourly ozone concentrations and meteorology were measured at 5 m above ground with a mobile system during one month each at different coastal and inland locations in the rural landscape of west Sweden. Ozone concentrations measured with the mobile system were compared with the simultaneous measurements at the permanent monitoring sites Östad and Råö. Ozone concentrations were related to the relative topography, which was defined as the altitude of the site subtracted with the mean altitude of the surrounding area within a radius of 3 km. Methodology x x x x x x x Lanna Hedared Sandhult Nidingen Råö Alafors x Östad x Brobacka x Rönnäng 3 km red cross; mobile system black cross; permanent monitoring sites

33 3 Three days with anticyclonic weather conditions. Only 8 km distance between Östad and Brobacka. Hourly ozone concentrations depend on the position in the landscape Östad Råö Brobacka 40 km Site typeRelative topo- graphy, m Altitude, m a.s.l. ÖstadInland valley-2363 BrobackaInland hilltop46167 RåöCoastal--

44 4 Diurnal ozone concentrations depend on distance to the coast and relative topography Östad Sandhult Hedared 40 km Nidingen Site typeRelative topo- graphy, m Altitude, m a.s.l. ÖstadInland valley-2363 HedaredInland valley SandhultInland hilltop38296 NidingenCoastal-- Hedared vs Östad Sandhult vs Östad Nidingen vs Östad

55 5 Diurnal ozone range correlated with relative topography The diurnal ozone concentra- tion range (DOR) of a certain inland site, relative to Östad (=1.0), could be significantly correlated to the relative topography of the specific site. Relative topography (m)  low high 

66 6 Diurnal ozone range correlated with diurnal temperature range The diurnal ozone concentration range (DOR) could be significantly correlated with the diurnal air temperature range (DTR) across all investigated locations. Blue; coastal Red; inland hilltop Green; inland valley

77 7 Diurnal temperature range correlated with daily air pressure The diurnal air temperature range (DTR) could be significantly correlated with daily air pressure for sites separated into different categories. Blue; coastal Red; inland hilltop Green; inland valley