Phil Russell, NASA Ames Research Center

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A Perspective on Aerosol Remote Sensing and
Climate Research TARFOX as a Stepping Stone to
the State of the Art
Phil Russell, NASA Ames Research Center
Kaufman Symposium 30 May-1 June 2007 Greenbelt,
MD
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Symposium Focus Five areas where Yoram had great
influence

• Passive remote sensing of aerosols, clouds and
  Earths surface
• Active remote sensing of clouds and aerosols
• Aerosol climate effects
• Regional experiments focusing on aerosols
• Future satellite missions

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• Passive remote sensing of aerosols, clouds and
  Earths surface
• Active remote sensing of clouds and aerosols
• Aerosol climate effects
• Regional experiments focusing on aerosols
• Future satellite missions

TARFOX was my first chance to collaborate with
Yoram on a major project. Given his involvement,
Its not surprising that TARFOX made
contributions in all 5 of these areas, especially
as a stepping-stone in a chain of field
experiments leading to the current state of the
art.
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A Chain of Field Experiments Measuring Aerosols
Their Effects on Atmospheric Radiation
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A Chain of Field Experiments Measuring Aerosols
Their Effects on Atmospheric Radiation
TARFOX, 1996
INTEX-A, 2004
ACE-Asia, 2001
CLAMS, 2001
ACE-2, 1997
INTEX-B, 2006
ADAM, 2003 EVE, 2004
PRIDE, 2000
SAFARI, 2000
Aerosol Optical Depth Derived from Upward
Scattered Solar RadianceAVHRR/NOAA 11,
June-Aug., Husar et al., J. Geophys. Res., 102,
16,889, 1997.
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TARFOX contributions to the 5 areas where Yoram
had great influence (Symposium Focus)

• Passive remote sensing of aerosols, clouds and
  Earths surface
• Active remote sensing of clouds and aerosols
• Aerosol climate effects (radiative forcing)
• Regional experiments focusing on aerosols
• Future satellite missions

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TARFOX Tropospheric Aerosol Radiative Forcing
Observational Experiment

• Hence, radiative forcing of climate was very much
  on our minds as we designed TARFOX

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Globally averaged forcings from IPCC
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A Dominant Question in TARFOX Planning
Would the aerosol radiative forcing be large
enough to measure?
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TARFOX as a Stepping Stone to the State of the
Art
STARS 1975
TARFOX 1996
INTEX-B 2006
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STARS Sutro Tower Aerosol and Radiation Study
Radiative Flux Closure Experiment
Russell et al., JAS 1979
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J. Atmos. Sci
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Calculated aerosol-induced change in upwelling
flux, DaF?
Russell, Kinne, Bergstrom, JGR 1997
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Reasons Local Forcing Exceeds Global
Includes ocean surface albedo, sun angle,
overlying atmos. trans.
Product 11 to 53
Assumption of Charlson et al. 1992, IPCC
1996.
Russell, Kinne, Bergstrom, JGR 1997
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TARFOX, 1996
Aerosol Optical Depth Derived from Upward
Scattered Solar RadianceAVHRR/NOAA 11,
June-Aug., Husar et al., J. Geophys. Res., 102,
16,889, 1997.
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TARFOX as a Stepping Stone to the State of the
Art
STARS 1975
TARFOX 1996
INTEX-B 2006
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TARFOX-measured and calculated aerosol-induced
changes in radiant flux (DaFlux?) vs AOD
We found the predicted flux changes!
24-hr avg. DaF (W m-2)
Aerosol Optical Depth (300-700 nm) above
Measurement
Hignett et al., JGR 1999 Russell et al., JGR
1999 (TARFOX issue)
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A Chain of Field Experiments Measuring Aerosols
Their Effects on Atmospheric Radiation
Radiative flux(l) closure forcing efficiency(l)
Radiative flux closure forcing efficiency
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J31 in INTEX-A/ICARTT Payload
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Climate Change Science in INTEX-A/ICARTT
Measurements of Aerosol Effects on the Solar
Energy that Drives Climate
Forcing Efficiency W m-2
Solar energy W m-2
Slope Aerosol Radiative Forcing Efficiency
Case 2,21 Jul2004
Case
Jetstream 31 (J31)
Aerosol Amount, AOD(499 nm)
Redemann et al., JGR, 2006

• Scientific Conclusions
• The gradients (spatial variations) in AOD that
  occur frequently off the US East coast provide a
  natural laboratory for studying effects of
  aerosol particles on solar energy, and hence on
  climate.
• For the average aerosol optical depth of 0.5 in
  the 10 cases shown above, aerosols on average
  reduced the incident visible radiation (near
  midday) by the amount of energy it would take to
  power one 40 W light bulb for every square meter
  of ocean surface (0.5 x -80 W m-2 -40 W m-2
  see right frame above).

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TARFOX as a Stepping Stone to the State of the
Art
STARS 1975
TARFOX 1996
INTEX-B 2006
25
TARFOX contributions to the 5 areas where Yoram
had great influence (Symposium Focus)

• Passive remote sensing of aerosols, clouds and
  Earths surface
• Active remote sensing of clouds and aerosols
• Aerosol climate effects (radiative forcing)
• Regional experiments focusing on aerosols
• Future satellite missions

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Using measured DaFlux vs AOD to find best-fit
aerosol SSA, w(550 nm)
24-hr avg. DaF (W m-2)
Aerosol Optical Depth (300-700 nm) above
Measurement
Hignett et al., JGR 1999 Russell et al., JGR
1999 (TARFOX issue)
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Comparison of Techniques to Determine Aerosol
Single Scattering Albedo
Russell et al., JGR, 1999b, Bergstrom Russell,
GRL,1999
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Comparison of Techniques to Determine Aerosol
Single Scattering Albedo
Hegg et al., JGR, 1997 Hartley et al., JGR, 2000
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Comparison of Aerosol Single Scattering Albedos
Derived by Diverse Techniques
Remer, Kaufman, Holben, JGR, 1999 Remer
Kaufman, JGR, 1998
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Comparison of Aerosol Single Scattering Albedos
Derived by Diverse Techniques
Redemann et al., JGR, 2000b
Russell et al., JAS 2001
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Two Experiments That Studied Aerosols in the
Polluted Marine Boundary Layer
ACE-2, 1997
TARFOX, 1996
Aerosol Optical Depth Derived from Upward
Scattered Solar RadianceAVHRR/NOAA 11,
June-Aug., Husar et al., J. Geophys. Res., 102,
16,889, 1997.
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Methods to Derive Aerosol Single Scattering Albedo
Spectrally resolved fluxes reduce this weakness
Russell et al., JAS 2001
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TARFOX contributions to the 5 areas where Yoram
had great influence (Symposium Focus)

• Passive remote sensing of aerosols, clouds and
  Earths surface
• Active remote sensing of clouds and aerosols
• Aerosol climate effects (radiative forcing
  local?regional)
• Regional experiments focusing on aerosols
• Future satellite missions

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Regional Assessment of Aerosol Radiative
ForcingNorth Atlantic, 25-60 N
Needs
Approach

• Combine Satellite and Suborbital Data

• ta(l,x,y,z,t)
• wa(l,x,y,z,t)
• ba(l,x,y,z,t)
• As(l,x,y,m0)

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Regional Assessment of Aerosol Radiative
ForcingNorth Atlantic, 25-60 N
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Regional Assessment of Aerosol Radiative
ForcingNorth Atlantic, 25-60 N
Satellite ta(0.5 mm,x,y,t)
Suborbital (TARFOX ACE-2)

• ta(l)/ta(0.5 mm) Sunphotometer Meas.
• ta(z) Sunphotom. Meas
• wa(l) 4 Techniques (Russell et al., JAS, 2001)
• ba(l,m0) Size distributions sunphot in situ
  meas
• As(m0) A/C Pyranometers

TARFOX 1996
ACE -2 1997
AVHRR, Jun-Aug Husar et al., JGR 1997
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Regional Assessment of Aerosol Radiative
ForcingNorth Atlantic, 25-60 N
Satellite ta(0.5 mm,x,y,t)
Satellite Suborbital DaFtropopause (W m-2)
-10 -8 -6 -4 -2 0
Net Flux Change (W m-2)
AVHRR, Jun-Aug Husar et al., JGR 1997
Tropopause, wa0.9, no clouds Bergstrom
Russell, GRL 1999
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TARFOX contributions to the 5 areas where Yoram
had great influence (Symposium Focus)

• Passive remote sensing of aerosols, clouds and
  Earths surface
• Active remote sensing of clouds and aerosols
• Aerosol climate effects (radiative forcing)
• Regional experiments focusing on aerosols
• Future satellite missions

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Comparison of Aerosol Single Scattering Albedos
Derived by Diverse Techniques
Russell et al., JAS 2001
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A Chain of Field Experiments Measuring Aerosols
Their Effects on Atmospheric Radiation
SSA from radiative flux closure
SSA(l) from radiative flux closure
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Aerosol Single Scattering Albedo Spectrum
Derived from measured flux and AOD
spectra. Desirable features
? Describes aerosol in its ambient state (incl
volatiles like water, organics, nitrates)? Wide
l range UV-Vis-SWIR? Includes l range of
OMI-UV, OMI-MW, MISR, MODIS, CALIPSO, HSRL, Glory
ASP, RSP, POLDER, ? Coalbedo (1-SSA) varies
by factor 4, l 350-900 nm
Single scattering albedo
12 April 2001, ACE-Asia
Bergstrom, Pilewskie, Schmid et al., JGR 2004
Wavelength, nm
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A Chain of Field Experiments Measuring Aerosols
Their Effects on Atmospheric Radiation
SSA from radiative flux closure
SSA(l) from radiative flux closure
SSA(l) from radiative flux closure
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SSA Spectra from 4 Experiments
Single Scattering Albedo
Wavelength, nm
Bergstrom et al., 2007
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Aerosol Absorption Optical Depth (AAOD) Spectra
from 5 Experiments
AAE
1.45
AAOD K l-AAE
2.27
Absorption Optical Depth
1.05
Absorption Angstrom Exponent (AAE)
2.34
1.12
For Black Carbon, AAE 1
Wavelength, nm
Bergstrom et al., 2007
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A Chain of Field Experiments Measuring Aerosols
Their Effects on Atmospheric Radiation
Chemical apportion-ment of AOD (optical-chemical
closure)?Importance of organics
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Another aspect of TARFOXs legacy Increased
recognition of the importance of the organic
component of aerosols. (and in general the
volatile components).
? This component is needed to get closure between
in situ and radiometric measurements (Hegg et
al.). ? Hence needed to get closure w satellite
measurements.
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A Chain of Field Experiments Measuring Aerosols
Their Effects on Atmospheric Radiation
Size-resolved chemical apportion-ment of
AOD?Importance of organics to submicron AOD
Chemical apportion-ment of AOD?Importance of
organics
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Importance of organics in ACE-Asia Size-resolved
composition
Wang et al., JGR 2002
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A Chain of Field Experiments Measuring Aerosols
Their Effects on Atmospheric Radiation
Size-resolved chemical apportion-ment of
AOD?Dominance of organics in Mexico
non-refractory component
Size-resolved chemical apportion-ment of
AOD?Importance of organics to submicron AOD
Chemical apportion-ment of AOD(closure)?Importa
nce of organics
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TARFOX as a Stepping Stone to the State of the
Art
STARS 1975
TARFOX 1996
INTEX-B 2006
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Wavelength dependence of absorption over Mexico
is linked to both the organic carbon component
(AMS - J, Jimenez, P. DeCarlo) and dust. Model
and remote sensing implications for SSA etc.
Aerosol Optics
Pollution

Shortwave Enhancement due to dust
Trend due to OC mass fraction
Expected value for pure BC
Dust
Shinozuka, Clarke et al., 2007
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Aerosol Absorption Optical Depth (AAOD) Spectra
from 5 Experiments
AAE
1.45
AAOD K l-AAE
2.27
Absorption Optical Depth
1.05
Absorption Angstrom Exponent (AAE)
2.34
1.12
For Black Carbon, AAE 1
Wavelength, nm
Bergstrom et al., 2007
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Evidence of enhanced absorption in near-UV from
SSA measurements
Barnard Volkamer, MILAGRO Mtg, May 2007
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SSA Spectra from 4 Experiments
Single Scattering Albedo
Wavelength, nm
Bergstrom et al., 2007
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Livingston, Torres, Veihelman et al., 2007
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Livingston, Bergstrom et al., 2007
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Larger OMI AOD retrievals over land likely due to
incorrect surface albedo assumption.

• Another promising explanation still being
  investigated effect of MILAGRO- measured
  wavelength-dependent SSA in UV.

Livingston, Bergstrom, Torres et al., 2007
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TARFOX contributions to the 5 areas where Yoram
had great influence (Symposium Focus)

• Passive remote sensing of aerosols, clouds and
  Earths surface satellite validation
• Active remote sensing of clouds and aerosols
• Aerosol climate effects (radiative forcing)
• Regional experiments focusing on aerosols
• Future satellite missions

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TARFOX as a Stepping Stone to the State of the
Art
STARS 1975
TARFOX 1996
INTEX-B 2006
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NASA Ames Airborne Tracking Sunphotometers
(AATS-6 AATS-14) in TARFOX
AATS-6
AATS-14
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Airborne Sunphotometer-Satellite Comparisons Over
Ocean
MODIS Airborne Simulator (550-2100 nm) vs AATS-6
(380-1000 nm)
MODIS (550-2119 nm) vs AATS-14 (354-2139 nm) vs
MISR vs OMI, multi grid cells
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AOD Comparisons, MODIS vs AATS Gulf of Mexico,
INTEX-B/MILAGRO, 2006
MODIS-Terra (March 5, 10, 12)
MODIS-Aqua (March 10, 17)
92 of points fall within band
100 of points fall within band
MODIS uncertainty band
Satellite (MODIS) AOD
37 cells
18 cells
MODIS wavelengths
Sunphotometer (AATS-14) AOD
Agreement at MODIS SWIR wavelengths is better
than expected, because the number of points
falling within the uncertainty band exceeds 66,
which is the expected fraction if the MODIS
uncertainty (0.03 0.05AOD) is 1s.
Redemann et al., 2007
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AATS-14
NASA Ames Airborne Tracking Sunphotometers
(AATS-6 AATS-14)
AATS-6
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Airborne Sunphotometer-Satellite Comparisons
Over Ocean
Satellite Instruments Compared To AATS AODs

• ATSR-2
• AVHRR
• GMS-5
• GOES-8

• MISR
• MAS
• MODIS-Aqua
• MODIS-Terra

• OMI
• RSP
• SeaWiFS
• TOMS

25 journal pubs
Nadir-viewing
Airborne Simulator of Satellite Instrument
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The A-Train is a set of satellites that fly in
sequence
Flying J31 under the A-Train provides opportunity
to compare AODs from AATS, MODIS, OMI
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AOD Comparisons, OMI vs AATS vs MODIS Gulf of
Mexico, INTEX-B/MILAGRO, 2006
(Prelim)
Larger OMI AOD retrievals over water likely due
to cloud contamination.
10 March 2006
(Prelim)
17 March 2006
Livingston et al., 2007
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Larger OMI AOD retrievals over water likely due
to cloud contamination.
Larger OMI AOD retrievals over land likely due to
incorrect surface albedo assumption.

• Another promising explanation still being
  investigated effect of MILAGRO- measured
  wavelength-dependent SSA in UV.

Livingston, Bergstrom, Torres et al., 2007
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Thanks to all those who made these results
possible

• The investigators who produced them (names on
  slides )
• The funders NASA, NSF, NOAA, DOE, Navy,

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