Characters Of The OMI NO₂ Column Densities In Zhejiang Province During 2005-2009

Nitrogen dioxide (NO₂) is one of the main pollutants in the urban atmosphere and plays a key role in the chemistry of the atmosphere. Measurements of the global distribution of the trace gas have become available with The Ozone Monitoring Instrument (OMI) onboard NASA's Aura Mission which was launched in July 2004. Along with the fast economic development, together with the high density of cities, Zhejiang province has being a typical region of air pollution as result of human activities. This article takes Zhejiang province as a test region. Based on the NO₂ (2005-2009) column densities products and the data of land use, the characters of NO₂ concentration over different ecosystem have been analyzed in Zhejiang Province. At the same time, the results of monthly average tropospheric NO₂ change trends over 11 cities of Zhejiang are presented, on the basis of OMNO₂ global product. Monthly average tropospheric NO₂ vertical column densities are acquired from OMNO₂ global product using Matlab and Arcgis tools. A linear sine model is used to fit these time series from January 2005 to December 2009 in Zhejiang province and cities. Change trend and growth rate of monthly average tropospheric NO₂ vertical column density is gained. Precision of change trend is also estimated.The results indicated that the tropospheric NO₂ column densities in Zhejiang increased distinctly from 2005 to 2009, and it showed distinct regional and seasonal variation characteristics. It has the highest concentration in winter while lowest in summer. The Tropospheric NO₂ column densities have been significantly distinction over different ecosystems. The Tropospheric NO₂ column densities have been significantly distinction over different ecosystems. It also presents zonal distribution and decreasing from northern to southern. Under the influence of the urbanization process, the highest NO₂ column densities appeared at cities and metroplexes which are located in the Hangzhou-Jiaxing-Huzhou plain, northern area of Ningbo as well as the west and east of Zhejiang. Moreover the lowest column densities appeared at the forest areas which are in the south and west of Zhejiang. In addition, it has the higher NO₂ column density over urban, cropland and water while lower values over forest. Along with the NO₂ column densities increasing, the higher NO₂ concentration increased quickly over urban, cropland and water, and the low NO₂ concentration increased obviously over the forest and grass land. The result also showed that in these cities a seasonal NO₂ maximum is found during winter time, the minimum is found during summer time. Seasonal cycle of the NO₂ vertical column density is very clear.This study confirms finally that remote sensing has a high application value in monitoring air pollution of city, and can overcome the short-comings of traditional methods.