Characteristics of atmospheric NO2 over China using OMI remote sensing data
利用OMI遥感数据研究中国区域大气NO2

The temporal-spatial characteristics of the tropospheric column NO2 (TroNO2) and total column NO2 (TotNO2) over China is analyzed using remote sensing data derived from OMI sensor. In general, the regional mean values of TroNO2 and TotNO2 have an increasing trend over China. The annual increasing rates are 4.67% and 2.21%, respectively. In addition, the TroNO2 and TotNO2 present annual variability. During the summer time, the TotNO2 has the largest value, while the TroNO2 has the smallest value. In contrast, TroNO2 has the largest value and the TotNO2 has a sub-peak value in the winter time. As the TroNO2 mainly comes from the troposphere in which human activity plays a dominant role, it indicates that the anthropogenic emission NOx is the main source of atmospheric NO2 in winter. The large values appear over northern China, Yangtze River Delta and Pearl River Delta regions, which is closely associated with urbanization and economic development. The variability of TroNO2 and TotNO2 as well as the ratio of TroNO2 and TotNO2 reflects the anthropogenic emission impact. For the change trend, the atmospheric NO2 is increasing over northern China and Yangtze River Delta regions, and is decreasing over Pearl River Delta region. Our results show that, the TroNO2 over northern China and Yangtze River Delta region were increased 23.78% and 25.73%, respectively, and the Pearl River Delta region was decreased 34.65% from late 2000 to late 2009. Over the Tibetan Plateau region, the TroNO2, TotNO2 and their ratio show a stable annual variability and a parabolic curve. The largest often appears in summertime, implying the pattern of natural emission. In Sichuan Basin, the NO2 shows another pattern, which is affected by more complex factors. TroNO2 and TotNO2 present close correlation, especially in the eastern industrial regions with larger correlation coefficients (correlation coefficients higher than 0.9 and ratios larger than 0.7).