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Reduction of Aerosol Absorption in Beijing since 2007: A Comprehensive Study

This study analyzes the reduction in aerosol absorption in Beijing since 2007 using MODIS and AERONET data. Key findings include changes in aerosol properties, sources, and impact of government measures. The results highlight a decrease in aerosol absorption, attributed to local and regional sources.

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Reduction of Aerosol Absorption in Beijing since 2007: A Comprehensive Study

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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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