Diurnal, seasonal, and annual trends in atmospheric CO at southwest London during 2000-2012: Wind sector analysis and comparison with Mace Head, Ireland

I.Y. Hernández-Paniagua, D. Lowry, K.C. Clemitshaw, R.E. Fisher, J.L. France, M. Lanoisellé, M. Ramonet, E.G. Nisbet

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In-situ measurements of atmospheric CO have been made at Royal Holloway University of London (RHUL) in Egham (EGH), Surrey, UK from 2000 to 2012. The data were linked to the global scale using NOAA-calibrated gases. Measured CO varies on time scales that range from minutes to inter-annual and annual cycles. Seasonality and pollution episodes occur each year. Diurnal cycles vary with daylight and temperature, which influence the biological cycle of CO and the degree of vertical mixing. Anthropogenic emissions of CO dominate the variability during weekdays when transport cycles are greater than at weekends. Seasonal cycles are driven by temporal variations in biological activity and changes in combustion emissions. Maximum mole fractions (μmol/mol) (henceforth referred to by parts per million, ppm) occur in winter, with minima in late summer. The smallest seasonal amplitude observed, peak to trough, was 17.0ppm CO in 2003, whereas the largest amplitude observed was 27.1ppm CO in 2008.Meteorology can strongly modify the CO mole fractions at different time scales. Analysis of eight 45° wind sectors shows that the highest CO mole fractions were recorded from the E and SE sectors. Lowest mole fractions were observed for air masses from the S and SW. Back-trajectory and meteorological analyses of the data confirm that the dominant sources of CO are anthropogenic emissions from London and SE England. The largest annual rate of increase in the annual average of CO, 3.26ppmyr (p
Original languageEnglish
Pages (from-to)138-147
Number of pages10
JournalAtmospheric Environment
Publication statusPublished - Mar 2015


  • carbon dioxide
  • Seasonal variation
  • Long-term trend

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