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

Recibido: 8 – october - 2004

3551

-Aerosol forcing of climate - Synergetic Rem. Sens

Yoram J. Kaufman and AERONET and MODIS aerosol teams.

Code 913, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA

PRESENTATION

ABSTRACT:

To study:

• Aerosol sources, transport and deposition

• Aerosol direct radiative forcing at TOA and at the surface

• Aerosol effect on cloud reflectance of sunlight

• Aerosol effect on cloud fraction, liquid water and precipitation

• Aerosol effect on evaporation

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To study:

• Aerosol sources, transport and deposition

• Aerosol direct radiative forcing at TOA and at the surface

• Aerosol effect on cloud reflectance of sunlight

• Aerosol effect on cloud fraction, liquid water and precipitation

• Aerosol effect on evaporation

Yoram Kaufman and AERONET and MODIS aerosol teams

Aerosol forcing of climate

-

Synergetic Rem. Sens.

(3)

2

MODIS

1-2 measurements a day

Global coverage

More accurate over the

oceans

Wide spectral range

Sensitive to reflected solar

flux

Some sensitivity to particle

size

AERONET

Continues daily sample

Global representation

Very accurate AOT

derivation -

better

representation over land

Wide angular range

Sensitive to transmitted

solar flux

(4)

3

MODIS

1-2 measurements a day

AERONET

Continues daily sample

0 0.5 1 1.5 2 0 0.5 1 1.5 2

0 0.5 1 1.5 2

0.5 1 0.5 1 0.5 1 1.5

0.001 0.01 0.1 1 10

1993-1999

Ratio

of

parameter

Terra

/

whole

day

Terra aerosol optical thickness at 0.55 µm Water Vapor

Optical Thickness Angstrom Exponent

MODIS Aerosol optical thickness of

coarse dust

and

fine pollution,

March 20,

2001 - separating the natural from the

anthropogenic

(5)

4

Both CO and fine mode

aerosol are produced by

urban pollution,

industrial combustion,

and biomass burning

Fine Mode AOT

CO Column Yoram Kaufman, NASA GSFC

David Edwards, NCAR

MOPITT CO

MODIS fine aerosols

Aerosol Optical Thickness

Aerosol

<->

fires

<->

CO

Sept. 2000

(6)

5

The dust maximum

moves North between

January to July.

Separating dust using

the

fine fraction, f:

f

dust

=0.5±0.05

f

maritime

=0.3±0.1

f

anthrop

=0.9±0.1

Dust depletion and

deposition with its

transport west

http://lake.nascom.nasa.gov/movas/

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6

0.04

0.06

0.08

0.1

0.12

0.14

0

1

2

3

4

5

6

Aerosol

optical

thickness

500

nm

Column precipitable water vapor (cm)

CAPE VERDE

L A N A I BERMUDA

KASHIDHOO

DRY TORTUGAS

SAN NICOLAS

ACSENSION ISLAND

T A H I T I N A U R U

τ

b a c k=.033+0.016exp(0.0027W 4 . 0

) r=0.88

0 . 1 7 1 0 . 3 0 5

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7

Dust deposition rates (tg/month) in 2001: MODIS measurements and

chemical transport models for the region (0°-40°N).

0

5

10

15

20

25

30

35

40

2

4

6

8

10

12

MODIS f

dust

=0.5, f

maritime

=0.3

Fan et al 2003, model 0-6 µm

Fan et al 2003, model 0-12 µm

Ginoux et al. [2001, 2003] model

MODIS f

dust

=f

maritime

=0.5

2001

Dust

deposition

(tg/month)

0°-40°N

Dust migration

240±80

tg left Africa at 0°-30°N

Deposition:

140±40

tg in the Atlantic Ocean,

50±15

tg in the Amazon Basin

-explaining the Amazon fertilization

paradox

- 50±25

tg arrive to the Caribbean.

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8

MODIS

Global coverage

AERONET

Global representation

ocean

land

both

AERONET sites

0 0.2 0.4 0.6 0.8 1

0 0.2 0.4 0.6 0.8 1

OCEAN 660 nm N = 2052

100 points 50 points 25 points 15 points

MODIS AOT (660 nm)

AERONET AOT (660 nm) y = 0.008 + 0.95 x R = 0.92

0 0.2 0.4 0.6 0.8 1

0 0.2 0.4 0.6 0.8 1 LAND 660 nm N = 5906

300 points 150 points 75 points 32 points

MODIS AOT (660 nm)

AERONET AOT (660 nm)

y = 0.059 + 0.70 x R = 0.68

66% of MODIS aerosol retrievals

over ocean fall within expected uncertainty

71% of MODIS aerosol retrievals

over land fall within expected uncertainty

MODIS aerosol validation 2000-2002

ocean

land

Remer et al. (2004)

Ichoku et al. 2002 Chu et al. 2002

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0

0.2

0.4

0.6

0.8

1

MODIS 16°N, 23°W

MODIS 17°N, 23°W

AERONET 16°43'N, 22°56'W

2000

2001

2002

2003

M J S D M J S D M J S D M J S D

Aerosol

optical

thickness

(11)

10

Stefan Kinne et al 2004

1998-2001

Only 2001

2001

2001

(12)

11

MODIS

Wide spectral range

AERONET

Wide angular range

MODIS: Saharan dust, Jan. 2002

Fires in Australia, Dec 2001

Visible

Mid IR

Visible

Mid IR

0.00

0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16

0.01 0.1 1 10 100

Radius, µm

τ(440)=0.04 τ(440)=0.05 τ(440)=0.07 τ(440)=0.10 τ(440)=0.16 τ(440)=0.21 τ(440)=0.34 τ(440)=0.45 τ(440)=0.59 τ(440)=0.68 τ(440)=0.92 0.1 1 10 1 0 0

0 30 60 90 1 2 0 1 5 0 1 8 0

Spheres (g = 0.78) Spheroids (g = 0.74)

Phase function (440 nm)

Scattering angles

(13)

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MODIS

Sensitive to reflected solar flux

AERONET

Sensitive to transmitted solar flux

-25 -20 -15 -10 -5

0 sect 1 sect 2 sect 3 sect 4

radiative effect (W/m 2 ) - 24hr average month

2000 2001 2002 2003 Ju Oc Ja A p Ju Oc Ja A p Ju Oc Ja A p Ju

30°-60°N -25 -20 -15 -10 -5

0 sect 5 sect 6 sect 7 sect 8

radiative effect (W/m 2 ) - 24hr average month

2000 2001 2002 2003 Ju Oc Ja A p Ju Oc Ja A p Ju Oc Ja A p Ju

0°-30°N -25 -20 -15 -10 -5 0

sect 9 sect 10 sect 11 sect 12 sect13

radiative effect (W/m 2 ) - 24hr average month

2000 2001 2002 2003 Ju Oc Ja A p Ju Oc Ja A p Ju Oc Ja A p Ju

0°-30°S 30°-60°S

sec 1 sec 2 sec 3 sec 4 sec 5 sec 6 sec 7 sec 8 sec 9 sec 10 sec 11 sec 12

---sec

13---Seasonal aerosol

Radiative effect at TOA

Remer et al., 2004

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Aerosol direct radiative forcing

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0 0.1 0.2 0.3 0.4 0.5 0.6

16 quadrants of the Earth Anmyon, Korea

E Asia

Capo Verde

Europe

WASHINGTON

India

Pacific Ocean

S Africa

fine

mode

fraction

of

optical

thickness

Aerosol optical thickness

more dust

more pollution

baseline oceanic aerosol

Christopher et al 2004

Classification of aerosol to natural

and anthropogenic

anthropogenic

dust

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14

Cooling

Heating No

absor-ption

25% absor-ption

Dubovik et al.,2002

(16)

15

Table 1: Summary of th e offset in the scatter plots of τabs vs. τscat. For each case the data were first averaged for several

ranges of τscat and then fitted with a linear fit. The uncertainty in the method is estimated to beΔτabs = ±0.002.

Location 0.44 µm 0.67 µm 0.87 µm 1.02 µm Lanai 0.0000 -0.0002 -0.0001 -0.0002 Tahiti 0.0039 0.0029 0.0025 0.0025 Nauru 0.0008 0.0005 0.0003 0.0004 Ascension

Island 0.0023 0.0037 0.0047 0.0054 Bermuda 0.0006 -0.0010 0.0004 -0.0001 All

maritime

0.0017± 0.0017

0.0017± 0.0019

0.0018± 0.0022

0.0020± 0.0025 Cart Site 0.0005 0.0004 -0.0001 0.0002 Turkey -0.0002 0.0011 0.0011 0.0014

Is there a cloud free

anomalous

absorption in the

atmosphere?

-AERONET

answers:

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16

Can AERONET do

even better?

• Southern Hemisphere

• Oceans

• Aerosol forcing at the surface

- longer

λ

s

• Refractive index - water

vapor - more polarization

• Use in chemical transport

models

• Cloud screening - help from

MODIS spatial variability in

the visible and 1.37 µm.

What AERONET introduced to

the aerosol measurements?

0 20 40 60 80 100 120

1999 2000 2001 2002 2003 2004

publication/yr

year

estimate fo 2004

• Reliable instruments

• Excellent calibration procedure /

record

• Direct broadcast - transparency of

problems

• AOT ==> size distribution,

absorption, ref index, non sphericity

• Openness web site accessibility

-wide use

• combination of AERONET data with

meteorological data, lidars, satellites

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17

Kaufman, Y.J., B. N. Holben, D. Tanré, et al: Will aerosol measurements from Terra and Aqua polar orbiting satellites represent the daily aerosol abundance and properties? GRL., 27, 3861-3864, 2000. Kaufman, Y. J., A. Smirnov, B. N. Holben and O. Dubovik, Baseline maritime aerosol: methodology to

derive the optical thickness and scattering properties, GRL., 28, 3251-3254, 2001

Tanré, D., Y. J. Kaufman, B.N. Holben, et al., Climatology of dust aerosol size distribution and optical properties derived from remotely sensed data in the solar spectrum, JGR, 106, 18205-18217, 2001

Kaufman, Y.J., B. N. Holben, S. Mattoo, et al: Aerosol radiative impact on spectral solar flux reaching the surface, derived from AERONET principal plane measurements, JAS, 59, 633-644, 2002.

Dubovik, O., B.N. Holben, T. F. Eck, et al: Climatology of aerosol absorption and optical properties in key worldwide locations, JAS, 59, 590-608, 2002

Kaufman, Y. J., D. Tanré and O. Boucher, A satellite view of aerosols in the climate system, Review for

Nature, 419, 215-223, Sept. 12, 2002

Remer, L. A., D. Tanré, Y. J. Kaufman, et al, Validation of MODIS aerosol retrieval over ocean. GRL., 29

(12): JUN 2002

Chu, D. A., Y. J. Kaufman, C. Ichoku, et al: Validation of MODIS aerosol optical depth retrieval over land,

GRL., 29 (12): JUN 2002

Kaufman, Y. J., O. Dubovik, A. Smirnov, and B. N. Holben, Remote sensing of non-aerosol absorption in cloud free atmosphere, GRL., 29 (18): SEP. 2002

Ichoku, C., L. A. Remer, Y. J. Kaufman, et al: MODIS observation of aerosols over Southern Africa during

SAFARI 2000: data, validation, and estimation of aerosol radiative forcing JGR 108 (D13): 2003

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