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Reduction of Aerosol Absorption in Beijing since 2007 from MODIS and AERONET

Reduction of Aerosol Absorption in Beijing since 2007 from MODIS and AERONET A. Lyapustin , A. Smirnov, B. Holben , M. Chin, R. Kahn, I. Slutsker , A. Sinyuk , Y. Wang, S. Korkin – NASA GSFC; D. G. Streets, Z. Lu – Argonne National Lab.; I. Laszlo, S. Kondragunta – NOAA STAR;

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Reduction of Aerosol Absorption in Beijing since 2007 from MODIS and AERONET

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  1. Reduction of Aerosol Absorption in Beijing since 2007 from MODIS and AERONET A. Lyapustin, A. Smirnov, B. Holben, M. Chin, R. Kahn, I. Slutsker, A. Sinyuk, Y. Wang, S. Korkin – NASA GSFC; D. G. Streets, Z. Lu – Argonne National Lab.; I. Laszlo, S. Kondragunta – NOAA STAR; D. Tanre, O. Dubovik, P. Goloub – Univ. Lille, France; H.-B. Chen - Institute of Atm. Physics, CAS, Beijing, China March 29, 2011

  2. TS Analysis of MAIAC-AERONET AOT over Beijing I II , 10km av. MODIS Terra nr=1.44; ni=0.008 (SSAvis~0.91) =0.15+0.05, =2.5+0.2 . I II MODIS Aqua • Low MAIAC bias of 10-20% at AOT peaks before ~mid-2007; no bias thereafter; • Regression slopes: 0.94→0.99 (Terra), and 0.91 →1.0 (Aqua); ni ~0.001; SSA~0.01

  3. MAIAC-AERONET Analysis Aqua Terra AERONET – MAIAC (AOT>0.4) AERONET Analysis (monthly averages) • L2 criteria: • ≥21 az. angles; • SZA≥50; • ≤5% residual; • AOT0.44>0.4 for SSA. Winter • Insignificant or no change in Ref of fine and coarse modes & in Angstrom exponent; • SSA increase by ~0.02 (0.017 without winter) in 9 years with significance level 0.88. • Similar increase (~0.03) for Xiang-He (60km southeast), and slight decrease for Taihu (~1000 km south of Beijing)

  4. Beijing Aerosol • Main Aerosol Sources: residential heating and cooking, industry, transportation; • Strong role of Regional Sources (Streets et al., 2007; Jia et al., 2008): • Rural NorthIndustrial South • (SSA~0.8-0.85) (SSA~0.9-0.95; secondary aerosols w. hygroscopic growth) • Source apportionment simulations (Matsui et al., 2009): • Local (primary): from 100km over 24h • Regional (secondary): from 500km over 3 days • Any aerosol realization is the superposition of • diurnal (Garland et al., 2009), • synoptic (~5-7 days) (Streets et al., 2007; Jia et al., 2008), • seasonal (Eck et al., 2010) patterns. From Jia, Y. et al., JGR, 113, D21309, 2008

  5. Discussion • Measures of Chinese gov. during preparation for Olympics-2008 to improve AQ in host cities, including Beijing and 5 surrounding provinces ($12.2B): • Converted >50,000 coal-burning homes to natural gas; • A number of industrial polluters were either modernized, including 16,000 coal-burning factories, or shut down by 2008; • Factories relocated from Beijing, including the 4th largest steel company (Shougang Group); • Raised diesel vehicle emission standard (Euro III →IV in Beijing; II →III for the rest of the country). • Total air pollution has reduced • in Beijing since 2005 (Lin et al., 2010); • during 2008 Olympics (Cermak and Knutti, 2009); • GDP grows over 9%/year • Number of cars grew 49% • Inventory-based Assessment of BC projects growth for Beiing (Streets and Lu, current communications) • Our finding: two independent techniques show reduction of aerosol absorption (BC) . • Confirmed by: long term meas. of PM chemical composition in Beijing (Okuda et al., 2011) report 33% BC reduction in 2008 as compared to the reference period of 2005-2007.

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