NOx emission trends over Chinese cities estimated from OMI observations during 2005 to 2015

摘要

Satellite nitrogen dioxide (NO) observations have been widely used toevaluate emission changes. To determine trends in nitrogen oxides (NO)emission over China, we used a method independent of chemical transportmodels to quantify the NO emissions from 48 cities and seven powerplants over China, on the basis of Ozone Monitoring Instrument (OMI) NOobservations from 2005 to 2015. We found that NO emissions over 48Chinese cities increased by 52 % from 2005 to 2011 and decreased by21 % from 2011 to 2015. The decrease since 2011 could be mainlyattributed to emission control measures in power sector; while cities withdifferent dominant emission sources (i.e., power, industrial, andtransportation sectors) showed variable emission decline timelines thatcorresponded to the schedules for emission control in different sectors. Thetime series of the derived NO emissions was consistent with thebottom-up emission inventories for all power plants ( = 0. 8 on average), butnot for some cities ( = 0. 4 on average). The lack of consistency observedfor cities was most probably due to the high uncertainty of bottom-up urbanemissions used in this study, which were derived from downscaling theregional-based emission data to city level by using spatial distribution proxies.