Temporal surface ozone patterns in urban Manitoba, Canada

• Published in: Boundary-layer meteorology 2001-06, Vol.99 (3), p.411-428
• Main Authors: RADDATZ, R. L, CUMMINE, J. D
• Format: Article
• Language: English
• Subjects: Applied sciences; Atmospheric boundary layer; Atmospheric pollution; Boundary layers; Canada, Manitoba; Chemical composition and interactions. Ionic interactions and processes; Earth, ocean, space; Emissions; Exact sciences and technology; External geophysics; Fumigation; Meteorology; Nitrogen oxides; Organic compounds; Ozone; Photochemicals; Pollutants physicochemistry study: properties, effects, reactions, transport and distribution; Pollution; Solar radiation; Stratosphere; Thunderstorms; Troposphere; Urban areas
• ISSN: 0006-8314; 1573-1472
• DOI: 10.1023/A:1018983012168

This study examined temporal surface ozone patternsfor two urban centres in Manitoba,Canada by analyzing hourly concentrations at theWinnipeg downtown (1995-1999), Winnipegresidential (1995-1999) and Brandon industrial(1998-1999) monitoring sites. The characteristicannual ozone cycle and diurnalcycles for June and December were attributable to: (1) theannual and diurnal solar radiation cycles,(2) temporal variations in the emissions of precursorchemical compounds, in particular the source strength ofnitrogen oxides, (3) temporal variationsin the height of the mixed layer, which determinethe degree of dilution of these emissions byatmospheric dispersion, and (4) an in situvolatile organic compound sensitive photochemicalregime, which resulted in decreased concentrations ofozone in response to increasedconcentrations of nitrogen oxides. Onlyone exceedance of the maximum acceptable level of82 ppb was recorded in the study period; itoccurred at the Brandon monitoring site on June 6, 1999.The sequence of weather and the hourly concentrationsof ozone and nitrogen oxides indicatedthat: (1) ozone fumigation, with the transition fromthe nocturnal boundary layer to the daytime mixed layer, mayhave supplemented photochemical ozone formation duringthe morning hours, and (2) during theevening hours, the post cold-frontal downward flux ofozone rich air, which was in the region dueto atmospheric transport, stratosphere-troposphere-exchangeor, possibly, due to the multiplicityof thunderstorms in the area in lateafternoon - early evening, may have been the main cause ofthis rare exceedance event.[PUBLICATION ABSTRACT]