1. ‘APEC Blue’ in North China simulated with the high resolution nested GEOS-Chem model Yixuan Gu 1,2, Hong Liao 1 1 State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences 2 University of Chinese Academy of Sciences The 7th International GEOS-Chem Meeting (IGC7)

2. OUTLINE 1.INTRODUCTION 2.MODEL AND EMISSIONS 3.MODEL VALUATION 4.MAIN RESULTS 5.SUMMARY

3. APEC BLUE (November 5  11, 2014) Clean days in Beijing during the Asia-Pacific Economic Cooperation (APEC) meeting, as a result of the tough emission-reduction measures.

4. Emission reductions during APEC Emission Reduction MeasuresDates Travel restriction by odd-even license numberNov. 3–12 The suspension of production by factoriesNov. 3–11 HolidaysNov. 7–12 Vehicles transporting construction waste and dangerous chemicals were barred Nov. 5–12 Emission reductions in Beijing and surrounding provinces (Hebei, Shandong, Shanxi, Henan and Inner Mongolia) Nov. 3–12 *According to EPA, SO 2, NO x, PM 10, PM 2.5, and VOCs emissions were reduced by 39.2%, 49.6%, 66.6%, 61.6% and 33.6%, respectively, in Beijing, and by about 30% in other areas in North China.

5. Meteorological conditions APEC Period (Nov. 5–11, 2014) Emission Control Period (Nov 3–12, 2014) N UNFAVORABLE factors: Low wind speed; No precipitation; Stable weather condition.

6. Model and emissions VERSION : v9-02 RESOLUTION: 4x5 0.25°x0.3125°nested grid MET : GEOS-FP Hebei Shandong Shanxi Henan Beijing topographic map SPECIESCHINA SO 2 (Tg S/yr)28.2 CO (Tg C/yr)168.2 NH 3 (Tg N/yr)9.1 NO x (Tg N/yr)27.9 OC (Tg C/yr)3.3 BC (Tg C/yr)1.8 Table 2 Annual emissions of aerosol precursors and aerosols in China (HTAP) HTAP EMISSIONS IN CHINA (Janssens-Maenhout et al., 2015 ， ACPD) Impact of emission control on air quality (PM 2.5 ) in Beijing with the unfavorable atmospheric conditions? Inner Mongolia

7. Model evaluation The model underestimates the concentrations of PM 2.5 by 50% because of the low biases in simulated sulfate and OC. A NORMAL CASE: 2014 Beijing Campaign Data (Feb. 24–Mar. 12, 2014)

8. Numerical experiments ExperimentsEmissions NO-CTRLEDGAR-HTAP emissions from Oct.1–Nov. 29, 2014 CTRL Emission control during APEC period (according to the EPA report) : Beijing: SO 2, NO x, and NMVOCs emissions reduced by 39.2%, 49.6%, and 33.6%, other precursors reduced by 30.0% ， respectively. North China: SO 2, NO x, CO, NH 3, NMVOCs emissions reduced by 30.0%.

9. Emission Control Period Oct. 1–Nov. 2 Nov. 3–12Nov. 13–29 Reduction rates during APEC relative to Oct. 1–Nov. 2 and Nov. 13–29 OBS112.748.8114.257% CTRL68.528.462.058% NO-CTRL68.539.666.340% Table 4 Comparisons of observed and simulated PM 2.5 concentrations (μg/m 3 ) in Beijing Reductions in PM 2.5 concentrations during APEC Beijing

10. SpeciesCTRLNO-CTRL(conc NO-CTRL -conc CTRL )/conc NO-CTRL sulfate3.482.4626.6% nitrate16.9512.3525.1% ammonium6.194.4925.1% OC7.835.5129.5% BC5.123.6029.7% PM 2.5 39.5728.4127.3% Reductions in PM 2.5 concentrations in Beijing during APEC (November 5  11, 2014)

11. Reduction in PM 2.5 concentrations during APEC North China  Simulated concentrations of PM 2.5 decreased by 43–51% during the APEC relative to other days in October and November in 2014.  Observed PM 2.5 concentrations decreased by 38%–51% during the APEC relative to other days in October and November in 2014.

12. Summary 1.Model evaluation during the APEC indicates that the model underestimates PM 2.5 concentrations in North China by about 50% because of the low biases in simulated sulfate and OC. 2.During the APEC emission control period of Nov. 3–12, 2014, both observed and simulated aerosol concentrations were significantly reduced; relative to the days before and after APEC, observed PM 2.5 concentrations showed reductions of 57% and simulated PM 2.5 concentrations showed reductions of 58%. 3.During APEC, simulated concentrations of SO 4, NO 3, NH 4, BC, OC, and PM 2.5 in Beijing with emission control measure exhibited decreases of 25– 30% relative to those simulated with no emission reductions.

13. THANKS FOR YOUR ATTENTION.