Weekly cycle of NO2 by GOME measurements: a signature of anthropogenic sources

[摘要] Nitrogen oxides(NO+NO₂=NO_x and reservoir species) are important trace gases in the tropospherewith impact on human health, atmospheric chemistry and climate. Besides natural sources (lightning, soilemissions) and biomass burning, fossil fuel combustion is estimated to be responsible forabout 50% of the total production of NO_x. Since human activity in industrialized countrieslargely follows a seven-day cycle, fossil fuel combustion is expected to be reducedduring weekends. This "weekend effect" is well known from local, ground basedmeasurements, but has never been analysed on a global scale before.

The Global Ozone Monitoring Experiment (GOME) on board the ESA-satellite ERS-2 allowsmeasurements of NO₂ column densities. By estimating and subtracting the stratospheric column,and considering radiative transfer, vertical column densities (VCD) of troposphericNO₂ can be determined (e.g. Leue et al., 2001). We demonstrate the statisticalanalysis of weekly cycles of tropospheric NO₂ VCDs for different regions of the world. In thecycles of the industrialized regions and cities in the US, Europe and Japan a clear Sundayminimum of tropospheric NO₂ VCD can be seen. Sunday NO₂ VCDs are about25-50% lower than working day levels. Metropolitan areas with other religious and cultural backgrounds(Jerusalem, Mecca) show different weekly patterns corresponding to different days of rest. InChina, no weekly pattern can be found.

The presence of a weekly cycle in the measured tropospheric NO₂ VCD may help to identify the differentanthropogenic source categories. Furthermore, we estimated the lifetime of troposphericNO₂ by analysing the mean weekly cycle exemplarily over Germany, obtaining a value of about6 h in summer and 18-24 h in winter.

[学科分类] 大气科学