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Analysis of diurnal patterns of surface ozone (O) at multiple urban sites in the UK shows the occurrence of prominent nocturnal enhancements during the winter months (November-March). Whilst nocturnal surface ozone (NSO) enhancement events have been observed at other locations, this is the first time that such features have been demonstrated to occur in the UK and the second location globally. The observed NSO enhancement events in the UK were found to be so prevalent that they are clearly discernible in monthly diurnal cycles averaged over several years of data. Long-term (2000-2010) analysis of hourly surface ozone data from 18 urban background stations shows a bimodal diurnal variation during the winter months with a secondary nighttime peak around 0300 hours along with the primary daytime peak. For all but one site, the daily maxima NSO concentrations during the winter months exceeded 60 μg/m on >20 % of the nights. The highest NSO value recorded was 118 μg/m. During the months of November, December, and January, the monthly averaged O concentrations observed at night (0300 h) even exceeded those observed in the daytime (1300 h). The analysis also shows that these NSO enhancements can last for several hours and were regional in scale, extending across several stations simultaneously. Interestingly, the urban sites in the north of the UK exhibited higher NSO than the sites in the south of the UK, despite their daily maxima being similar. In part, this seems to be related to the sites in the north typically having lower concentrations of nitrogen oxides. [ABSTRACT FROM AUTHOR]

Abstract: A technique is described to independently validate the national emission inventories produced using the methodology of the Intergovernmental Panel on Climate Change (IPCC). A boundary layer budget approach is applied to the United Kingdom and an inverse modelling technique is used to derive total and spatial apportionment of emissions for CO, CO2, CH4, N2O, HFC-134a, HCFC-141b, HCFC-142b and HCFC-22. During the summer of 2005 and September 2006 an aircraft circumnavigating the UK was used to collect data upwind and downwind of the UK coast. The concentration measurements were inverted to produce mapped emissions of the UK. The modelled overall CO flux (2900 ± 107 kt yr−1) and spatial apportionment throughout the UK are remarkably consistent with the official UK NAEI (National Atmospheric Emission Inventory) inventory. The CO2 total emissions (620 ± 105 Mt yr−1) and spatial apportionment are also close to the NAEI. However for N2O and CH4, the estimated annual fluxes, 500 ± 370 kt yr−1 and 3500 (range 0–8000 kt yr−1) respectively, are larger than the NAEI albeit with significant uncertainty. Emissions of four halocarbon compounds were also calculated with total emissions of 3.1 ± 0.4 kt yr−1 for HFC-134a, 0.9 ± 0.6 kt yr−1 for HCFC-141b, 0.56 ± 0.2 kt yr−1 for HCFC-142b and 3.8 ± 1.0 kt yr−1 for HCFC-22 consistent with other published data. [ABSTRACT FROM AUTHOR]