Regional modeling of tropospheric NO2 vertical column density over East Asia during the period 2000–2010: comparison with multisatellite observations

摘要

Satellite observations of the tropospheric NO vertical column density(VCD) are closely correlated to, and thus can be used to estimate, surfaceNO emissions. In this study, the NO VCD simulated by a regionalchemical transport model with emissions data from the updated RegionalEmission inventory in ASia (REAS) version 2.1 were validated throughcomparison with multisatellite observations during the period 2000–2010. Rapid growth in NO VCD (~11% year)driven by the expansion of anthropogenic NO emissions wasidentified above the central eastern China (CEC) region, except for theperiod during the economic downturn. In contrast, slightly decreasing trends(~2% year) were identified above Japan accompanied by adecline in anthropogenic emissions. To systematically compare the modeledNO VCD, we estimated sampling bias and the effect of applying theaveraging kernel information, with particular focus on the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) data.Using the updated REAS, the modeled NO VCD reasonably reproducedannual trends observed by multisatellites, suggesting that the rate ofincrease of NO emissions estimated by the updated REAS inventory would berobust. Province-scale revision of emissions above CEC is needed to furtherrefine emission inventories. Based on the close linear relationship betweenmodeled and observed NO VCD and anthropogenic NO emissions, NOemissions in 2009 and 2010, which were not covered by the updated REASinventory, were estimated. NO emissions from anthropogenic sources in Chinain 2009 and 2010 were determined to be 26.4 and 28.5 Tg year, respectively,indicating that NO emissions increased more than twofold between 2000 and2010. This increase reflected the strong growth of anthropogenic emissionsin China following the rapid recovery from the economic downturn from late2008 until mid-2009. Our method consists of simple estimations fromsatellite observations and provides results that are consistent with themost recent inventory of emissions data for China.