Characterization of NO₂ Pollution Changes in Beijing Using GOME Satellite Data

Nitrogen dioxide (NO₂) is known to cause respiratory problems for humans in the urban atmosphere and plays a key role in the control of the strong oxidant such asozone of the atmosphere. Measurements of the global distribution of tropospheric NO₂ column densities have become available with the Global Ozone Monitoring Experiment (GOME) instrument which is launched in April 1995 on board the ERS-2 satellite. The seasonal variation and trend of NO₂ over Beijing is analyzed using monthly averaged tropospheric NO₂ column data from GOME measurements from January 1996 to December 2002. The monthly averaged GOME NO₂ column present distinct variation characteristics with high values in January, February, November and December, and with low values in June, July and August. The results of analysis of GOME data reveal that NO₂ pollution in Beijing had been aggravated from 1996 to 2002 in general, with serious pollution happening in the years of 2002. The highest monthly averaged NO₂ column is found to occur in December 2002 with a value of 3.7×10¹⁶ molecules· cm^-2, increasing by 45 percent and 125 percent with comparison to the highest GOME monthly averaged NO₂ column before December 2002 (that is 2.5×10¹⁶ molecules·cm^-2 in December 1999) and the monthly averaged NO₂ column in November 2002 (that is 1.6×10¹⁶ molecules·cm^-2), respectively. Furthermore, the seasonal variation of GOME tropospheric NO₂ column over Beijing is compared with that of monthly averaged surface mass concentration of NO₂, which are calculated according to the daily pollution index of NO₂ for Beijing for a period from 1 January 2001 to 31 December 2002. Both GOME tropospheric NO₂ column density and surface NO₂ mass concentration present the same distinct seasonal variation characteristics, with high values in winter and low values in summer. It shows that for the comparison period the variations of monthly averaged tropospheric NO₂ columns over Beijing are well consistent with the variations of the monthly averaged surface NO₂ mass concentrations in Beijing. The correlative coefficient is as high as 0.86. It can be concluded that GOME tropospheric NO₂ column data can be used to analyze the seasonal variation and trend of NO₂ pollution over a specific region.