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
1
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.
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
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
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
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/
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
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.
8
MODIS
Global coverage
AERONET
Global representation
ocean
land
both
AERONET sites
0 0.2 0.4 0.6 0.8 10 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
9
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
10
Stefan Kinne et al 2004
1998-2001
Only 2001
2001
2001
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
0.000.02 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
12
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
13
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
14
Cooling
Heating No
absor-ption
25% absor-ption
Dubovik et al.,2002
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:
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
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