Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 9 3 2009 10.5194/acpd-9-12927-2009 http://www.atmos-chem-phys-discuss.net/9/12927/2009/ http://www.atmos-chem-phys-discuss.net/9/12927/2009/acpd-9-12927-2009.html http://www.atmos-chem-phys-discuss.net/9/12927/2009/acpd-9-12927-2009.pdf 12927 12963 2009-06-08 Theoretical implication of reversals of the ozone weekend effect systematically observed in Japan A. Kannari kannari.akiyoshi@circus.ocn.ne.jp T. Ohara Independent researcher, NIES visiting researcher, Tokyo, Japan National Institute for Environmental Studies (NIES), Tsukuba, Japan Systematic changes of the ozone weekend effect are found over broad areas of Japan. These changes are characterized by (1) spatial reversals from a weekend increase in the vicinity of huge precursor source areas to a weekend decrease in the surrounding rural areas, and (2) temporal reversals from a weekend increase under relatively unsuitable meteorological conditions for ozone formation to a weekend decrease under relatively suitable conditions. We developed a simple numerical advection-reaction model to explain the relationship between the duration of advection and the supplied solar energy, which causes the daily maximum ozone concentration to be lower near the precursor source. Ozone isopleth diagrams for individual advection durations (equivalent to the distance from the source) for a wide range of initial precursor conditions show that both VOC-limited and NO_x-limited regimes exist for each advection duration, but the area of NO_x-limited regime becomes dominant as the advection duration increases because of the increased exposure of the air mass to solar energy. For given initial VOC and NO_x concentrations, the area remote from the source becomes a NO_x-limited regime even if the precursor source area is in the VOC-limited regime. The rate of reduction of weekend emissions of NO_x is larger than that of VOC, causing a weekend increase in a VOC-limited regime near the source, but a weekend decrease in remote areas with a NO_x-limited regime. 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