Aerosol Optical Properties in Southeast Asia From AERONET Observations

T.F. Eck 1, B.N. Holben 1, J. Boonjawat 2, A. Snidvongs 2, H.V. Le 3, J.S. Schafer 1, T. Kaewkonga 2, R. Mongkolnavin 2,

J.S. Reid 4, L.A. Remer 1, O. Dubovik 1, and A. Smirnov 1

1NASA / GSFC, Greenbelt, MD, USA2Chulalongkorn University, Bangkok, Thailand

3Vietnam National Center for Natural Science and Technology, Hanoi, Vietnam4NRL, Monterey, CA, USA

AERONET-An Internationally Federated Network

Characterization of aerosol optical propertiesValidation of Satellite Aerosol RetrievalsNear real-time acquisition; long term measurementsHomepage access http://aeronet.gsfc.nasa.gov

AERONET Monitoring of Aerosol Optical Properties in SE Asia

• Mid-February to Early May, 2003 : 2nd Half of the Dry Season at 6 Sites; Entire Dry Season monitoring at 1 site Nov 2003 - Present

•First Year of AERONET Monitoring in Thailand and Vietnam, with Plans for Continuing Monitoring

• Preliminary Analysis Based on Level 1.5 Data: Awaiting Final Calibration for More Complete Analysis (4 sites have final level 2.0 data)

Chulalongkorn University, Bangkok

Phimai, Thailand site: Left to right- Mr. Khun Kamol (Site Manager); Tom Eck (AERONET); Dr. Jariya Boonjawat (Thailand coordinator of AERONET)

Project Atmospheric Brown Cloud

ABC Observatories

SE Asia AERONET Sites: February-May 2003

Except Mukdahan - started in Nov 03

Composite TERRA-MODIS Image on MAR 11 of 2004TERRA-MODIS Granule Overpass Times:

0350, 0345 UTC AERONET Web-Site

AOD (500 nm)

Bangkok - 0.88

Phimai -0.60

Mukdahan - 0.95

April 7, 2003; SeaWiFS image - Smoke and pollution covers a large portion of the SE Asia region and advecting out over the South China Sea

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

40 60 80 100 120

4 Sites in Thailand Daily Ave. AOT Feb 16 - May 7, 2003Level 1.5 Preliminary Cloud Screened

Om KoiPhimai Hua HinChula

Aer

osol

Op

tica

l D

epth

(50

0 n

m)

Day of Year - 2003

Om Koi - webs data filteredPhimai - 2 cloudy days removed

The first half of the monitoring period Feb 16 - Mar 21 (until Day 80) showed relatively low AOD in NW Thailand at the Om Koi site (1120 m elev) on mountain ridge top, and the highest AOD at the Phimai site. After Mar 21, the AOD was relatively high at all sites as large amounts of biomass burning smoke affected parts of the region.

0.00

0.20

0.40

0.60

0.80

2 3 4 5

Monthly Average AOD (500 nm) Dry Season (2nd half: Feb-May) Cloud Screened

PhiMai, THBangkok, THOm Koi, THHua Hin, THBac Giang, VNBac Lieu, VN

Aer

osol

Opt

ical

Dep

th (

500

nm

)

Month

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2 3 4 5

Monthly Average Angstrom Exponent Dry Season (2nd half: Feb-May) Cloud Screened

PhiMai, THBangkok, THOm Koi, THHua Hin, THBac Giang, VNBac Lieu, VN

An

gstr

om E

xpon

ent

(440

- 8

70 n

m)

Month

AERONET-MODIS Comparison of AOD retrievals

MODIS Retrievals - SE Asia April and May 2003

0.00

0.05

0.10

0.15

0.20

0.1 1 10

Phimai, Thailand Feb - May, 200314 Almucantars/ AOD bin; AOD(440)>0.4

Level 2.0 Final Cal. & Cloud Screening

0.450.520.660.830.971.22

dV

/ d

(ln

r)

[ m

3/

m2]

Radius (m)

0.86

0.88

0.90

0.92

0.94

0.96

400 500 600 700 800 900 1000 1100

Phimai, Thailand Feb - May, 200314 Almucantars/ AOD bin; AOD(440)>0.4

Level 2.0 Final Cal. & Cloud Screening

0.450.520.660.830.971.22

Sin

gle

Sca

tter

ing

Alb

edo

Wavelength (nm)

AOD 440 nm

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.1 1 10

Comparison of SE Asian Aerosol Size Distributionsfor AOD (440 nm) ~ 0.70

Om Koi - 0.68Bangkok - 0.70PhiMai - 0.66Hua Hin - 0.72Bac Giang - 0.67

dV

/ d (

ln r

) [ m

3/

m2]

Radius (m)

0.85

0.86

0.87

0.88

0.89

0.90

0.91

0.92

0.93

400 500 600 700 800 900 1000 1100

Southeast Asia AERONET Sites - 2003 Dry SeasonSingle Scattering Albedo Comparison - AOD(440)>0.4

All Cloud Screened Observations

Om KoiBangkokPhiMaiHua HinBac Giang

Sin

gle

Scat

teri

ng

Alb

edo

Wavelength (nm)

0.004

0.006

0.008

0.010

0.012

0.014

0.016

400 500 600 700 800 900 1000 1100

Southeast Asia AERONET Sites - 2003 Dry SeasonImaginary Refractive Index Comparison - AOD(440)>0.4

All Cloud Screened Observations

Om KoiBangkokPhimaiHua HinBac Giang

Imag

inar

y R

efac

tive

In

dex

Wavelength (nm)

0.00

0.50

1.00

1.50

2.00

2.50

Nov

/1/0

3

Dec

/1/0

3

Dec

/31/

03

Jan

/31/

04

Mar

/1/0

4

Mar

/31/

04

May

/1/0

4

Mukdahan, Thailand Dry Season Nov 2003 - April 2004

Daily Average AOD

380 nm Ave.=0.76501 nm Ave.=0.56870 nm Ave.=0.24

Aer

osol

Op

tica

l D

epth

0.50

1.00

1.50

2.00

Nov

/1/0

3

Dec

/1/0

3

Dec

/31/

03

Jan

/31/

04

Mar

/1/0

4

Mar

/31/

04

May

/1/0

4

Mukdahan, Thailand Dry Season Nov 2003 - April 2004

Daily Average Angstrom Exponent

WEXP 440/870 : Ave. = 1.45

An

gstr

om E

xpon

ent

(440

/870

nm

)

Entire Dry Season Monitoring at Mukdahan, Thailand

0.00

0.50

1.00

1.50

2.00

2.50

Nov

/1/0

3

Dec

/1/0

3

Dec

/31/

03

Jan

/31/

04

Mar

/1/0

4

Mar

/31/

04

May

/1/0

4

Mukdahan, Thailand Dry Season Nov 2003 - April 2004

Daily Average AOD

380 nm Ave.=0.76501 nm Ave.=0.56870 nm Ave.=0.24

Aer

osol

Op

tica

l D

epth

0.80

0.85

0.90

0.95

1.00

Nov

/16/

03

Dec

/21/

03

Jan

/25/

04

Feb

/29/

04

Ap

r/4/

04

May

/9/0

4

Mukdahan, Thailand Dry Season Nov 2003 - April 2004AOD(440 nm)>0.4; SZA > 45 deg.

440 nm670 nm870 nm

Sin

gle

Scat

teri

ng

Alb

edo

Level 1.5 data

0.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

Nov

/16/

03

Dec

/21/

03

Jan

/25/

04

Feb

/29/

04

Ap

r/4/

04

May

/9/0

4

Mukdahan, Thailand Dry Season Nov 2003 - April 2004AOD(440 nm)>0.4; SZA > 45 deg.

Rv(fine)

Fin

e M

ode

Rad

ius

(m

)

0.000

0.005

0.010

0.015

0.020

0.025

Nov

/16/

03

Dec

/21/

03

Jan

/25/

04

Feb

/29/

04

Ap

r/4/

04

May

/9/0

4

Mukdahan, Thailand Dry Season Nov 2003 - April 2004AOD(440 nm)>0.4; SZA > 45 deg.

440 nm670 nm870 nm

Ref

ract

ive

Ind

ex (

Imag

inar

y)

Dry Season Trends in Single Scattering Albedo - Mukdahan

Preliminary - Level 1.5 Data

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.1 1 10

Comparison of Biomass Burning Regions - Size Distributionsfor AOD (440 nm) ~ 0.70

Om Koi -1.81 AlphaAmazonian ForestBoreal ForestSouth American CerradoAfrican Savanna

dV

/ d

(ln

r)

[ m

3/

m2]

Radius (m)

0.75

0.80

0.85

0.90

0.95

400 500 600 700 800 900 1000 1100

Comparison of Thailand Biomass Burning SSAversus Other Biomass Burning Regions

Om Koi, ThailandAmazoniaBoreal ForestS. American CerradoAfrican Savanna

Sin

gle

Sca

tter

ing

Alb

edo

Wavelength(nm)

Amazon, Boreal, Cerrado, and Savanna data from Dubovik et al. [2002] Table 1.

Washington, Paris, and Mexico City data from Dubovik et al. [2002] Table 1.

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.1 1 10

Comparison of Urban Areas - Size Distributionsfor AOD (440 nm) ~ 0.70

BangkokBeijingWashington DC (GSFC)Paris (Creteil)Mexico City

dV

/ d

(ln

r)

[ m

3/

m2]

Radius (um)

0.80

0.85

0.90

0.95

1.00

400 500 600 700 800 900 1000 1100

Comparison of 'Urban' Single Scattering AlbedoAverage of all retrievals with AOD(440)>0.4

BangkokBeijingWashington DC (GSFC)Paris (Creteil)Mexico City

Sin

gle

Sca

tter

ing

Alb

edo

Wavelength(nm)

Urban AERONET sites - Comparison

Average Angstrom Exp (440-870 nm) = 1.56 on Feb 25 at Phimai, Thailand

SSA = ~0.94 - 0.92; Rvfine = ~0.17 m

February 25, 2003 - High AOD (1.12 at 500 nm) at Phimai ; 8-Day Back Trajectory suggests transport of both pollution from industrial area SE of Bangkok and possibly also smoke and pollution from SW Cambodia and Viet Nam

April 15, 2003 - High AOD (1.25 at 500 nm) at Om Koi ; 8-Day Back Trajectory suggests transport of both smoke and pollution from Burma, the Bay of Bengal, India and Pakistan

Average Angstrom Exp (440-870 nm) = 1.55 on Apr 15 at Om Koi

SSA = ~0.89 spectrally flat; Rvfine = ~0.15 m

0.00

0.20

0.40

0.60

0.80

1.00

JA

N

FE

B

MA

R

AP

R

MA

Y

JU

N

JU

L

AU

G

SE

P

OC

T

NO

V

DE

C

Ye

ar

Kanpur, India Monthly Ave. Aerosol Optical Depth (500 nm)Years 2001 & 2002

Aer

osol

Opt

ical

Dep

th (

500

nm

)

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

JAN

FE

B

MA

R

AP

R

MA

Y

JUN

JUL

AU

G

SE

P

OC

T

NO

V

DE

C

Yea

r

Kanpur, India Monthly Ave. Angstrom ExponentYears 2001 & 2002

An

gstr

om E

xpon

ent

(440

-870

nm

)

Average Angstrom Exp (440-870 nm) = 1.15 on May 5, 2003 at Om Koi

Rvfine = ~0.15 m

May 5, 2003 - AOD ~0.2 at 500 nm at Om Koi; 8-Day Back Trajectory suggests transport of mixed fine and coarse mode aerosol from India

June 1, 2003 - High AOD (~1.50 at 500 nm) at Bac Giang; 5-Day Back Trajectory suggests transport of fine mode aerosol from China

SSA = ~0.96 spectrally flat; Rvfine = ~0.25 - 0.30 m

Average Angstrom Exp (440-870 nm) = 1.25 on Apr 15 at Bac Giang, Viet Nam

SUMMARY AND CONCLUSIONS

• Preliminary data suggest that during the 2nd half of the dry season the aerosol is quite strongly absorbing in both urban and rural sites in SE Asia (0550 ~ 0.895 - 0.915)

• Aerosol size distributions are dominated by fine mode particles (radius < 0.6 micron) with very consistent size of fine particles at all sites (rv ~ 0.15 - 0.16 m at a440 = 0.7)

•Data from Phimai suggest a dynamic aerosol model with particle size increasing as optical depth increases, and 0 also increasing as optical depth increases

• Mukdahan data (level 1.5) suggest a dry season decrease in Single scattering albedo from Nov - Apr with coincident decrease in fine mode particle size and increase in REFimag

Biomass-burning Aerosols in South East-Asia: Smoke Impact Assessment (BASE-ASIA, US

Participation)

Biomass-burning Aerosols in South East-Asia: Smoke Impact Assessment (BASE-ASIA, US

Participation)Si-Chee Tsay, N. C. Hsu , Q. Ji, M. D. King, G. Molnar

NASA Goddard Space Flight Center, Greenbelt, Maryland B. Huebert

University of Hawaii, Honolulu, HawaiiL. Marufu, R. R. Dickerson and J. Stehr

University of Maryland, College Park, MarylandD. Savoie

University of Miami, Miami, FloridaW.-Y. Sun and K. J. Yang

Purdue University, West Lafayette, Indiana

NASA/GSFC Collaborators: K.-M. W. Lau, B. Holben, M. Jhabvala, Y. Kaufman, P. K. Shu, A. Thompson, C. J. Tucker

3 April 2001Terra/MODIS True ColorRayleigh scattering removed

BASE-ASIA

• Research Goals: aerosol-cloud interactions, impacts on cloud lifetime and precipitation.

• Approach: synergy of measurements from satellites, remote-sensing & in-situ aircraft, and ground-based network, and regional modeling.

smoke

cloud

interaction

Pre-monsoon season in Southeast Asia: A Terra MODIS view showing distinct large-scale smoke, cloud & interaction regions.24 March 2004

SeaWiFS True Color

Pochanart et al., JGR, 2003

0.0

0.5

1.0

1.5

2.0

40 60 80 100 120

Phimai, Thailand Elevation 220 mDaily Ave. AOT Feb 17 - May 7, 2003Level 1.5 Preliminary Cloud Screened

AOT 380 : 0.79AOT 500 : 0.56AOT 868 : 0.23

Aer

osol

Op

tica

l D

epth

Day of Year - 2003

0.6

0.8

1.0

1.2

1.4

1.6

1.8

40 60 80 100 120

Phimai, Thailand Elevation 220 mDaily Ave. Alpha Feb 17 - May 7, 2003Level 1.5 Preliminary Cloud Screened

An

gstr

om E

xpon

ent

(440

-870

)

Day of Year - 2003

Angstrom Exponent was typically >1.4 : Therefore Fine mode particles (radius <0.6 micron) dominated

SE Asia AERONET Sites: February-May 2003

April 8, 2003 - Numerous fires in India, Burma, and Laos and NW Thailand -

Om Koi: AOD(500nm)=0.45 at Aqua (MODIS) Satellite Overpass time