Weekly cycles in tropospheric NO2 content over urban regions
S.A. Sitnov, T.G. Adix
A. M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, Moscow, Russia, 119017, Pyzhevskii per., 3, Moscow, Russia
sitnov@ifaran.ru
Keywords: nitrogen dioxide NO2, tropospheric NO2 column, weekly cycle, urban agglomeration, Moscow region, Kruskal–Wallis test, diurnal cycle, seasonal dependence
Abstract
Using tropospheric nitrogen dioxide (NO2) columns obtained by OMI instrument, the analysis of NO2 intraweek changes over the world largest urban agglomerations (including Moscow) was carried out. With the help of Kruskal–Wallis test the estimates of statistical significance of differences in NO2 content between different days of the week were obtained. It was found that over all considered agglomerations tropospheric NO2 content is higher during workdays than during weekend. The peak-to-peak amplitudes of the statistically significant weekly cycles vary in the range from 14 (Cairo, Jakarta) up to 64% (Los Angeles). Intraweek differences of NO2 over densely populated Shanghai and Delhi are statistically insignificant and do not exceed 7%. The NO2 weekly cycle over the Moscow agglomeration is investigated in more detail. The changes in the spatial distribution of tropospheric NO2 content over the Moscow region in the course of week were analysed. Using the data from three ground-based stations of air pollution control network in Moscow the weekly cycles in surface NO2 concentrations were investigated and statistical significance of the intraweek differences of them was tested. The weekly cycle in tropospheric NO2 column over Moscow was compared with those in surface NO2 concentrations and a satisfactory agreement was found. The transformation of diurnal courses in surface NO2 concentrations during a week in the summer and winter periods was also analyzed.
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