Detection from space of a reduction in anthropogenic emissions of nitrogen oxides during the Chinese economic downturn

Abstract

Abstract. Rapid economic and industrial development in China and relatively weak emission controls have resulted in significant increases in emissions of nitrogen oxides (NO x ) 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 NO 2 retrieved from satellite observations by SCIAMACHY, GOME-2 and OMI (both by KNMI and by NASA) are used to evaluate changes in emissions of NO x 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 NO 2 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 NO x 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 NO 2 . 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 %.

Satellite constraint for emissions of nitrogen oxides from anthropogenic, lightning and soil sources over East China on a high-resolution grid

“…That anthropogenic emissions inferred from space are larger than bottom-up inventories for China is consistent with results from many previous studies (Jaeglé et al, 2005;Wang et al, 2007;Zhang et al, 2007;Lin and McElroy, 2011). Our a posteriori budget for anthropogenic emissions over East China is similar to the value of 0.565 TgN for July 2007 estimated by Zhao and Wang (2009).…”

“…They are however about half of the inverse estimate by Wang et al (2007) who suggested soil emissions to be more than 40 % of anthropogenic emissions in summer of 1997-2000. In concluding, anthropogenic emissions are found to be the dominant source of NO x over East China for 2006, even in summer when natural sources reach maximum values. The contribution of anthropogenic emissions most likely has increased in more recent years due to their rapid growth (Lin and McElroy, 2011). In the future, the anthropogenic contribution may continue to increase along with the rapid economic and industrial development, if emission control is not taken successfully.…”

“…The total model error from factors other than emissions of NO x is estimated to be about 30-40 % (Martin et al, 2003;Wang et al, 2007;Lin and McElroy, 2011); in this study, the value of 40 % is taken for the inversion purpose. (Fig.…”

Regional modeling of tropospheric NO<sub>2</sub> vertical column density over East Asia during the period 2000–2010: comparison with multisatellite observations

“…Long-term simulations between 2000 and 2010 with relatively high resolution (80 km) were made using a regional-scale, full-chemistry model, the most valuable aspect of this study. Previous studies of emission trends and their variability were conducted with relatively coarse resolution (e.g., Lin and McElroy, 2011;Lamsal et al, 2011). The fine-scale resolution used in the present study will enable comparison among emission inventories.…”

Impact of the 2008 Global Recession on air quality over the United States: Implications for surface ozone levels from changes in NOx emissions

“…Satellite NO 2 observations from OMI and other sensors show detectable decreasing trends in NO 2 VCD during the recession (data not shown here). Earlier observations and model simulations [Zhang et al, 2008;Lin and McElroy, 2011;Zhang et al, 2011] have shown that Asian pollution outflow contribute a significant portion of background ozone in western North America. For instance, Zhang et al [2011] estimated that intercontinental pollution (by all emissions outside the United States) and anthropogenic methane enhance background O 3 by 9 ppbv at low-altitude sites and 13 ppbv at high-altitude sites.…”