Aerosol Optical Properties in Southeast Asia From AERONET Observations

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ÓPTICA PURA Y APLICADA – Vol. 37, núm. 3 - 2004

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).

(1) NASA / GSFC, Greenbelt, MD, USA. (2) Chulalongkorn University, Bangkok, Thailand.

(3) Vietnam National Center for Natural Science and Technology, Hanoi, Vietnam. (4) NRL, Monterey, CA, USA.

ABSTRACT:

• Characterization of aerosol optical properties. • Validation of Satellite Aerosol Retrievals.

• Near real-time acquisition; long term measurements. • Homepage access http://aeronet.gsfc.nasa.gov

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

• 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.

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

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 (w0550 ~ 0.895 - 0.915).

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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

_{NASA / GSFC, Greenbelt, MD, USA}

2

_{Chulalongkorn University, Bangkok, Thailand}

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AERONET-

An Internationally Federated Network

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AERONET Monitoring of Aerosol Optical

Properties in SE Asia

•First Year of AERONET Monitoring in

Thailand and Vietnam, with Plans for

Continuing Monitoring

• 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

• Preliminary Analysis Based on Level 1.5

Data: Awaiting Final Calibration for More

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Project Atmospheric Brown Cloud

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SE Asia AERONET Sites: February-May 2003

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

0350, 0345UTC

AERONET Web-Site

AOD (500 nm)

Bangkok - 0.88

Phimai -0.60

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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, 2003

Level 1.5 Preliminary Cloud Screened

Om Koi

Phimai

Hua Hin

Chula

Aerosol Optical Depth (500 nm)

Om Koi - webs data filtered Phimai - 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

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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, TH

Bangkok, TH Om Koi, TH Hua Hin, TH Bac Giang, VN Bac Lieu, VN

Aerosol Optical Depth (500 nm)

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, TH

Bangkok, TH Om Koi, TH

Hua Hin, TH

Bac Giang, VN Bac Lieu, VN

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AERONET-MODIS

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0.00 0.05 0.10 0.15 0.20

0.1 1 10

Phimai, Thailand Feb - May, 2003 14 Almucantars/ AOD bin; AOD(440)>0.4

Level 2.0 Final Cal. & Cloud Screening

0.45 0.52 0.66 0.83 0.97 1.22

dV/ d (ln r) [

µm

3 /

µm

2 ]

Radius (µm)

0.86 0.88 0.90 0.92 0.94 0.96

400 500 600 700 800 900 1000 1100

Phimai, Thailand Feb - May, 2003 14 Almucantars/ AOD bin; AOD(440)>0.4

Level 2.0 Final Cal. & Cloud Screening

0.45 0.52 0.66 0.83 0.97 1.22

Single Scattering Albedo

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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 Distributions for AOD (440 nm) ~ 0.70

Om Koi - 0.68

Bangkok - 0.70

PhiMai - 0.66

Hua Hin - 0.72 Bac Giang - 0.67

dV/ d (ln r) [

µm 3 / µm 2 ] 0.85 0.86 0.87 0.88 0.89 0.90 0.91 0.92 0.93

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

All Cloud Screened Observations

Om Koi

Bangkok

PhiMai

Hua Hin Bac Giang

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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 Season Imaginary Refractive Index Comparison - AOD(440)>0.4

All Cloud Screened Observations

Om Koi Bangkok

Phimai

Hua Hin Bac Giang

Imaginary Refactive Index

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0.00 0.50 1.00 1.50 2.00 2.50 Mukdahan, Thailand Dry Season Nov 2003 - April 2004

Daily Average AOD

380 nm Ave.=0.76 501 nm Ave.=0.56 870 nm Ave.=0.24

Aerosol Optical Depth

0.50 1.00 1.50 2.00

Mukdahan, Thailand Dry Season Nov 2003 - April 2004 Daily Average Angstrom Exponent

WEXP 440/870 : Ave. = 1.45

Angst

rom Exponent

(

440/870 nm)

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0.00 0.50 1.00 1.50 2.00 2.50

Nov/1/03 Dec/1/03 _Dec/31/03 _Jan/31/04 Mar/1/04 _Mar/31/04 May/1/04 Mukdahan, Thailand

Dry Season Nov 2003 - April 2004 Daily Average AOD

380 nm Ave.=0.76 501 nm Ave.=0.56

870 nm Ave.=0.24

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0.80 0.85 0.90 0.95 1.00 N ov/16/03 D ec/21/03

Jan/25/04 Feb/29/04 A

p

r/4/04

May/9/04

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

440 nm

670 nm

870 nm

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 Apr/4/04 May/9/04

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

Rv(fine) Fin e Mod e Rad iu s ( µm) 0.000 0.005 0.010 0.015 0.020 0.025 N ov/16/03 D ec /21/03 Jan/25/04 Fe b/29/04 A p r/ 4/04 May/9/04 Mukdahan, Thailand Dry Season Nov 2003 - April 2004 AOD(440 nm)>0.4; SZA > 45 deg.

440 nm 670 nm 870 nm

R

efractive Index (Im

aginary)

Dry Season Trends in Single Scattering Albedo - Mukdahan

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0.00 0.02 0.04 0.06 0.08 0.10 0.12

0.1 1 10

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

Om Koi -1.81 Alpha

Amazonian Forest

Boreal Forest

South American Cerrado African Savanna

dV/ d (ln r) [

µm

3 /

µm

2 ]

Radius (µm)

0.75 0.80 0.85 0.90 0.95

400 500 600 700 800 900 1000 1100

Comparison of Thailand Biomass Burning SSA versus Other Biomass Burning Regions

Om Koi, Thailand

Amazonia

Boreal Forest

S. American Cerrado African Savanna

Wavelength(nm)

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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 Distributions for AOD (440 nm) ~ 0.70

Bangkok

Beijing

Washington DC (GSFC)

Paris (Creteil) Mexico City

dV/ d (ln r) [

µm 3 / µm 2 ] 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 Albedo Average of all retrievals with AOD(440)>0.4

Bangkok

Beijing

Washington DC (GSFC)

Paris (Creteil) Mexico City

Wavelength(nm)

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

SSA = ~0.94 - 0.92; Rv = ~0.17 µm

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0.00 0.20 0.40 0.60 0.80 1.00

JAN FEB MAR APR MAY JUN JUL _AUG SEP OCT NOV DEC Year

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

Aerosol Optical Depth (500 nm)

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40

JAN FEB _MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Year

Kanpur, India Monthly Ave. Angstrom Exponent Years 2001 & 2002

An gstrom Exp o n en

t (440-870 n

m

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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; Rv_fine= ~0.25 - 0.30 µm

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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 (

ω

₀

₅₅₀

~ 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 (r

_v

~ 0.15 - 0.16

µ

m at

τ

_a440

= 0.7)

•Data from Phimai suggest a dynamic aerosol model with

particle size increasing as optical depth increases, and

ω

₀

also

increasing as optical depth increases

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