Abstract
Abstract. Rapid economic and industrial development in China and relatively weak emission controls have resulted in significant increases in emissions of nitrogen oxides (NOx) in recent years, with the exception of late 2008 to mid 2009 when the economic downturn led to emission reductions detectable from space. Here vertical column densities (VCDs) of tropospheric NO2 retrieved from satellite observations by SCIAMACHY, GOME-2 and OMI (both by KNMI and by NASA) are used to evaluate changes in emissions of NOx from October 2004 to February 2010 identifying impacts of the economic downturn. Data over polluted regions of Northern East China suggest an increase of 27–33 % in 12-month mean VCD of NO2 prior to the downturn, consistent with an increase of 49 % in thermal power generation (TPG) reflecting the economic growth. More detailed analysis is used to quantify changes in emissions of NOx in January over the period 2005–2010 when the effect of the downturn was most evident. The GEOS-Chem model is employed to evaluate the effect of changes in chemistry and meteorology on VCD of NO2. This analysis indicates that emissions decreased by 20 % from January 2008 to January 2009, close to the reduction of 18 % in TPG that occurred over the same interval. A combination of three independent approaches indicates that the economic downturn was responsible for a reduction in emissions by 9–11 % in January 2009 with an additional decrease of 10 % attributed to the slow-down in industrial activity associated with the coincident celebration of the Chinese New Year; errors in the estimate are most likely less than 3.4 %.
Highlights
Nitrogen oxides (NOx≡nitric oxide (NO) + NO2) are an important constituent in the troposphere, affecting the formation of ozone and aerosols and acid deposition
MACHY, Richter et al (2005) showed that vertical column densities (VCDs) of NO2 increased by about 50 % over industrial regions of China in tropospheric VCDs of NO2 retrieved from SCIAMACHY, GOME-2 and OMI are used to evaluate the impact of the ecobetween 1996 and 2004
VCDs of tropospheric NO2 retrieved from SCIAMACHY, GOME-2 and OMI are used in this study to evaluate changes in emissions of nitrogen oxides (NOx) from October 2004 to February 2010
Summary
Nitrogen oxides (NOx≡NO + NO2) are an important constituent in the troposphere, affecting the formation of ozone and aerosols and acid deposition. MACHY, Richter et al (2005) showed that VCDs of NO2 increased by about 50 % over industrial regions of China in tropospheric VCDs of NO2 retrieved from SCIAMACHY, GOME-2 and OMI are used to evaluate the impact of the ecobetween 1996 and 2004 Their findings were supported nomic downturn on emissions of NOx. The inferred emission by subsequent studies Dates of holiday 9–15 February 29 January–4 February 18–24 February 6–12 February 25–31 January 13–19 February in this region (Fig. 2), an important factor contributing to a reduction in the uncertainties associated with the representativeness of the data applicable to the analysis of changes in emissions of NOx. Sections 2 and 3 introduce Chinese TPG data and four satellite products for VCDs of tropospheric NO2 employed in this study.
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