2009-07-06: Reductions of air pollution detected from space during the 2008 Beijing Olympic Games.

During the 2008 Olympic and Paralympic Games in Beijing (from 8 August to 17 September), local authorities enforced strong measures to reduce air pollution during the events. Inside and outside Beijing traffic was restricted, polluting industry was shut down temporarily and construction activities were put on hold.
To evaluate the direct effect of these measures, Mijling et al. 2009 used the tropospheric nitrogen dioxide tropospheric column observations from the satellite instruments GOME-2 and OMI. By interpreting these data against simulations from the regional chemistry transport model CHIMERE a reduction of nitrigen dioxide concentrations of approximately 60% is found above Beijing during the Olympic period. The air quality measures were especially effective in the Beijing area, but also noticeable in surrounding cities of Tianjin (30% reduction) and Shijiazhuang (20% reduction). After the Olympic Games the concentrations do not return immediately to their pre-Olympic values, suggesting that air quality in Beijing has improved systematically or that economic activity is only slowly recovering.
Mean tropospheric NO2 concentrations as observed by GOME-2 during the Olympic events in Beijing in 2008, compared with observations in the same period in 2007. Due to intensive air quality measures during the Olympic Games, the high NO2 concentration in Beijing strongly reduce, while high concentrations in the cities of Tianjin (at 110 km) and Shijiazhuang (at 250 km) persist.
The calculated reduction of tropospheric NO2 columns during the Olympic Games obtained by comparing GOME-2 with CHIMERE model results. This comparison is used to compensate for atypical meteorological conditions. A reduction of NO2 concentrations of approximately 60% is found above Beijing. The air quality measures were especially effective in the Beijing area, but also noticeable in surrounding cities of Tianjin (30% reduction) and Shijiazhuang (20% reduction).