THE TREND, SPATIAL TEMPORAL DISTRIBUTION AND SOURCES OF TROPOSPHERIC NO_2 OVER CHINA BASED ON SATELLITE MEASUREMENT DURING 1997 TO 2006

摘要

The characteristics of spatial and temporal distribution of tropospheric NO_2 column density concentration over China are presented, on the basis of measurements from the satellite instruments GOME and SCIAMACHY. From these observations, monthly averaged tropospheric NO_2 variations are determined for the period of 1997 to 2006. The trend and seasonal cycle are also investigated. The possible source of tropospheric NO_2 over megacity area is discussed in this paper. The results show a large growth of tropospheric NO_2 over eastern China, especially above the industrial areas with a fast economical growth, such as, Yangtze Rive Delta region and Pearl River Delta region because of the prominent anthropogenic activity. There is a rapid increase of tropospheric NO_2 over megacities in China. For instance, Shanghai had a linear significant increase in NO_2 columns of-20% per year (reference year 1997) in the period of 1997-2006, which is the rapidest increase among all the selected cities. The seasonal pattern of the NO_2 concentration shows a difference between east and west in China. In the eastern part of China, an expected winter maximum in seasonal cycle is found because of the prominent anthropogenic activity and meteorological conditions. In the western part this cycle shows a NO_2 maximum in summer time, which is attributed to natural emissions, especially soil emissions and lightning. A quickly increasing vehicle population may contribute to the increase of tropospheric NO_2 over megacities in China for the remarkable correlation for vehicle population with tropospheric NO_2.