Temporal and spatial analyses on distribution of NO2 column density in Yangtze Delta region

Based on the remote sensing data of GOME and SCIMACHY, the paper analyzes the variation trend, temporal and spatial characteristics of NO₂ column density from Apr. 1996 to Nov. 2009 in Yangtze Delta region. Besides that, seasonal analyses are also taken. In this session, a whole year is divided into dry season and rainy season. In spatial analyses, the paper emphasizes on the difference between NO₂ column density over the land and the sea located in study area. In addition, some comparative analyses are carried out on monthly average data of NO₂ column density and chlorophyll-a (Chl-a) concentration, in order to explore the relationship between the 2 factors and influence of NO₂ in global carbon cycling, as a part of research on global change. The research result shows that: (1) From 1996 to 2009, the NO₂ column density over Yangtze Delta Region increases, with some fluctuation. (2) The value of NO₂ column density has a higher value in the beginning and the end of the year, while it gets lower in the middle of a year. The value that in dry season is apparently higher than that in rainy season. (3)The spatial analyses show that the column density over land is higher than that over sea on average. Though changing consistently, temporal change of column density over land has a little lag behind that over the sea. (4) The spatial distribution pattern of the value in study area is relatively stable. The place in city of Nanjing, almost all of southern part of Jiangsu Province and Shanghai has a high value, and the place with a low value is in southern part of Zhejiang Province and open sea area to the east of Zhejiang Province. The value in other part of study area is moderate. (5) The variation trend of NO₂ column density and Chl-a concentration is almost opposite. Also, it can be proved that there is no linear relationship between the two parameters.