1. J. Ding 1,2, R. J. van der A 1, B. Mijling 1, P. F. Levelt 1,2, and N. Hao 3 [1] Royal Netherlands Meteorological Institute (KNMI), De Bilt, the Netherlands [2] Delft University of Technology, Delft, the Netherlands [3] German Aerospace Center (DLR), Oberpfaffenhofen, Germany Correspondence to: J. Ding (jieying.ding@knmi.nl) NOx emission estimates during 2014 Youth Olympic Games in Nanjing * * Ding, J., van der A, R. J., Mijling, B., Levelt, P. F., and Hao, N.: NO x emission estimates during the 2014 Youth Olympic Games in Nanjing, Atmos. Chem. Phys., 15, 9399-9412, doi:10.5194/acp-15-9399-2015, 2015

2. Outline Introduction Methods Improvement of emission estimates Emission analysis Conclusions

3. Introduction 2008 Olympic Games in Beijing 2010 Asian Games in Guangzhou 2013 Asian Youth Games in Nanjing 2014 Youth Olympic Games in Nanjing (“Youth Olympic Games blue sky”) 2014 Asia-Pacific Economic Cooperation in Beijing (“APEC blue sky”) Events with emission reductions

4. Nanjing Capital of Jiangsu province Population: 8.2 million Youth Olympic Games Date: 16 to 24 August, 2014 Regulations taken by local government

5. PeriodRegulations 1 st May - 30 th June The local government started to shut down the coal-burning factories. 1 st July - 15 th JulyAll coal-burning factories have been shut down. 16 th July - 31 st July The work on one third of construction sites was stopped. The parking fees in downtown increased sevenfold. 1 st August – 15 th August The work on 2000 construction sites was stopped. Heavy- industry factories reduced manufacturing by 20 percent. Vehicles with high emissions were banned from the city. Open space barbecue restaurants were closed. 900 electric buses and 500 taxis have been put into operation. 16 th August-31 st AugustThe work at all construction sites was put on hold.

6. Methods DECSO (Daily Emission estimates Constrained by Satellite Observation) DECSO Satellite observations of NO2 concentration Chemical transport model Inversion method based on extended Kalman filter More details in Mijling and van der A (2012, JGR)

7. NO 2 satellite observations OMI Overpass time: 13:30 local time Spatial resolution: 24 x 13 km 2 in nadir till 150 x 28km 2 at the end of swath Filter: Cloud radiance fraction larger than 70% Surface albedo larger than 20% Clouds below 800 hPa 4 pixels at either side of the swath (after filtering the largest pixel size is 75x21 km 2 )

8. Chemical transport model CHIMERE Domain: East Asia (18 – 50 o N, 102 – 132 0 E ) Horizontal resolution: 0.25 0 x 0.25 0 Vertical resolution: 8 layers up to 500 hPa Meteorological data: ECMWF Initial emission inventory: MEIC (2010) for China, INTEX-B (2006) for outside China

10. Improvement of Emission estimates New version of CHIMERE model Old one: CHIMERE V2006 Landuse: The Global Land Cover Facility (1994) New one: CHIMERE V2013 Biogenic emissions, new transport schemes, secondary organic aerosol chemistry, updated chemical reaction rates New landuse data: GlobCover Land cover (2009) Model improvement 19952009

11. Ground measurements Website: aqicn.org based on China National Urban air quality real-time publish platform Location: Nanjing People’s government (center of Nanjing) The only ground measurements we can find have a lot of limitations

12. Model comparison

13. Absolute Observation minus Forecast (OmF)

14. Quality control of satellite data

15. April to October, 2013 70% OmF in [-5, 10] November, 2013 to March, 2014 50% OmF in [-5, 10] Unrealistic Whole domain 2013 97% OmF in [-5, 10]

16. OmF criterion OmF in the interval of [-5, 10] 1e15 molecules/cm 2 For example: CHIMERE runs with DECSO emissions and MEIC emissions In 2013 summer in Nanjing ∆NOx emissions 9.2 1e15 molecules/cm 2 /h ∆NOx column concentration: 4.8 1e15 molecules/cm 2 OmF of 5 1e15 molecules/cm 2 NOx emission change of 9.6 1e15 molecules/cm 2 /h Remove all emissions in Nanjing or add 2 large-sized coal-fired power plants in a single day Remove all emissions in Nanjing or add 2 large-sized coal-fired power plants in a single day

17. Emission analysis No significant improvement in surface NO 2 concentration during the game period A decrease of 32% in August. But this could be caused by the rainy weather.

18. Emission reduction A reduction of about 25% A reduction of about 10%

19. Conclusions New CHIMERE is better performing than old CHIMERE. OmF filtering is necessary to avoid wrong emission estimates. The OMI observations show a 32% decrease in NO 2 column during the YOG. DECSO results show NO x emissions have a reduction of at least 25% during the YOG period and afterwards. The observed NO 2 columns and the derived emissions show different patterns that provide complimentary information. DECSO has the capacity to capture the change of NO x emissions on a monthly scale.

20. Any questions? Thank you.