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

TS Analysis of MAIAC-AERONET AOT over Beijing

MODIS Terra

MODIS Aqua

1. Low MAIAC bias of 10-20% at AOT peaks before ~mid-2007; no bias thereafter;

2. Regression slopes: 0.94→0.99 (Terra), and 0.91 →1.0 (Aqua); ni ~0.001; SSA~0.01

I II

I II

nr=1.44; ni=0.008 (SSAvis~0.91)

FvR =0.15+0.05, CvR =2.5+0.2 .

, 10km av.

MAIAC-AERONET Analysis

AERONET – MAIAC (AOT>0.4)

AERONET Analysis (monthly averages)

L2 criteria: • ≥21 az. angles;• SZA≥50; • ≤5% residual;• AOT0.44>0.4 for SSA.

1. Insignificant or no change in Ref of fine and coarse modes & in Angstrom exponent;

2. SSA increase by ~0.02 (0.017 without winter) in 9 years with significance level 0.88.

3. Similar increase (~0.03) for Xiang-He (60km southeast), and slight decrease for Taihu (~1000 km south of Beijing)

Terra Aqua

Winter

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 North Industrial 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

DiscussionMeasures 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.