Analysis of crop residue burning and tropospheric NO2 vertical column density retrieved from satellite remote sensing in North China.

To insure air quality during the Beijing Olympic Games, open field burning of crop residues was banned in North China from May to September in 2008. The impact of this effort was estimated through the detection of the crop residue burning from MODIS data and measurement of NO2 vertical column density retrieved from OMI data. The middle and thermal infrared channels of MODIS data were used to monitor the crop residue burning from June to August in 2007 and 2008. The number of crop residue burning pixels obviously decreased from about 250d in 2007 to less than 40d in 2008 in June and July, but there was a little increase in August. Meanwhile, the monthly averaged tropospheric NO2 vertical column density retrieved from OMI data from June to August in 2007 and 2008 were used to study the difference of the variation of NO2 in these two years, and the results indicated that NO2 concentration had been reduced due to the ban of crop residue burning to some extent, but the impact of this effort was limited.