Remote sensing of tropospheric aerosols from space past present and future
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Remote Sensing of Tropospheric Aerosols from Space: Past, Present, and Future. Michael D. King, 1 Yoram J. Kaufman, 1 Didier Tanré 2 and Teruyuki Nakajima 3 1 NASA Goddard Space Flight Center, Greenbelt, MD USA 2 Université des Sciences des Techniques de Lille, Villeneuve d’Ascq, France

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Remote sensing of tropospheric aerosols from space past present and future
Remote Sensing of Tropospheric Aerosols from Space: Past, Present, and Future

Michael D. King,1 Yoram J. Kaufman,1 Didier Tanré2 and Teruyuki Nakajima3

1NASA Goddard Space Flight Center, Greenbelt, MD USA

2Université des Sciences des Techniques de Lille, Villeneuve d’Ascq, France

3Center for Climate System Research, University of Tokyo, Japan

Outline

  • Physical principles behind the remote sensing of aerosol parameters

  • International satellite sensors enabling remote sensing of tropospheric aerosols

    • AVHRR, TOMS, ATSR-2, OCTS, POLDER, SeaWiFS, MISR, MODIS, AATSR, MERIS, GLI, and OMI

  • Instrument characteristics

    • Spacecraft, spatial resolution, swath width, sensor characteristics, and unique characteristics

  • Aerosol retrieval from existing satellite systems

  • Future capabilities

  • Opportunities for the future


Reflection function as a function of aerosol optical thickness
Reflection Function as a Function of Aerosol Optical Thickness

  • The reflection function is given by

    R(ta, w0; µ, µ0, f) =

  • The greatest sensitivity of reflected solar radiation to aerosol optical thickness occurs when

    • the surface reflectance is small

    • the single scattering albedo is large (small absorption)

    • larger slant angles (µ < 1)

pI(0, –µ, f)

µ0F0


Misr provides new angle on haze
MISR Provides New Angle on Haze Thickness

  • In this MISR view spanning from Lake Ontario to Georgia, the increasingly oblique view angles reveal a pall of haze over the Appalachian Mountains


Aerosol properties
Aerosol Properties Thickness

  • Eight MODIS bands are utilized to derive aerosol properties

    • 0.47, 0.55, 0.65, 0.86, 1.24, 1.64, 2.13, and 3.75 µm

    • Ocean

      • reflectance contrast between cloud-free atmosphere and ocean reflectance (dark)

      • aerosol optical thickness (0.47-2.13 µm)

      • size distribution characteristics (ratio between the assumed two log-normal modes, and the mean size of each mode)

    • Land

      • dense dark vegetation and semi-arid regions determined where aerosol is most transparent (2.13 and 3.75 µm)

      • contrast between Earth-atmosphere reflectance and that for dense dark vegetation surface (0.47 and 0.66 µm)

      • enhanced reflectance and reduced contrast over bright surfaces (post-launch)

      • aerosol optical thickness (0.47 and 0.66 µm)


Aerosol effects on reflected solar radiation over land
Aerosol Effects on Reflected Solar Radiation over Land Thickness

Biomass burning

Cuiabá, Brazil (August 25, 1995)

10 km

q0 = 36°

R = 0.66 µm

G = 0.55 µm

B = 0.47 µm

R = 1.65 µm

G = 1.2 µm

B = 2.1 µm

20 km


Surface reflectance at near infrared wavelengths
Surface Reflectance at Near-Infrared Wavelengths Thickness

  • Surface reflectance is high at 2.2 µm, moderate at 0.66 µm, and low at 0.49 µm

  • The aerosol effect on reflected solar radiation is small at 2.2 µm and large at 0.49 µm

  • MODIS operational algorithm over land assumes

Kaufman et al. (1997)

Ag(0.47 µm) = 0.5Ag(0.66 µm)

= 0.25Ag(2.1 µm)


Dynamic aerosol models
Dynamic Aerosol Models Thickness

Remer et al. (1996)

  • Accumulation mode particles (r < 0.3 µm) of mostly organic smoke particles or sulfates depend on optical thickness

  • Aerosol-free troposphere plus stratospheric aerosol (0.3 µm < r < 0.8 µm)

  • Maritime salt particles in the mid-Atlantic region (0.8 µm < r < 2.5 µm)

  • Coarse particles (r > 2.5 µm)




Aerosol properties1
Aerosol Properties Space

Land

Ocean

Land-Ocean

Cloud Mask

Polarization

Polarization-Ocean

Polarization-Land-Ocean

Not Used for Aerosols

Hyperspectral

AVHRR

TOMS

ATSR-2/AATSR

OCTS

POLDER

SeaWiFS

MISR

MODIS

MERIS

GLI

OMI

1.0

0.8

0.6

Transmission

0.4

0.2

0.0

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Wavelength (µm)


Aerosol properties2
Aerosol Properties Space

Near-infrared and thermal infrared

Land

Ocean

Land-Ocean

Cloud Mask

Not Used for Aerosols

AVHRR

ATSR-2/AATSR

OCTS

MODIS

GLI

1.0

0.8

0.6

Transmission

0.4

0.2

0.0

1.0

1.5

2.0

3.0

4.0

6.0

10.0

20.0

15.0

Wavelength (µm)




Tropospheric aerosol data record
Tropospheric Aerosol Data Record Space

1987

2002

1981

1983

1984

1986

1989

1990

1992

1993

1995

1996

1998

1999

2001

2004

1982

1985

1988

1991

1994

1997

2000

2003

InstrumentSpacecraft

AVHRR NOAA-7, 9, 11, 14, L, Metop-1

TOMS Nimbus-7, Meteor, EP, ADEOS, QuikTOMS

ATSR-2 ERS-2

OCTS ADEOS

POLDER ADEOS ADEOS II

SeaWiFS OrbView-2

MISR Terra

MODIS Terra

Aqua

USA

Europe

Japan


Tropospheric aerosol data record1
Tropospheric Aerosol Data Record Space

1987

2002

1981

1983

1984

1986

1989

1990

1992

1993

1995

1996

1998

1999

2001

2004

1982

1985

1988

1991

1994

1997

2000

2003

InstrumentSpacecraft

AATSR Envisat-1

MERIS Envisat-1

GLI ADEOS II

OMI Aura

USA

Europe

Japan


Aerosol optical thickness
Aerosol Optical Thickness Space

AVHRR

April 1997

No Data

0.0

0.1

0.2

0.3

0.4

0.5

Aerosol Optical Thickness (0.63 µm)


Aerosol optical thickness1
Aerosol Optical Thickness Space

TOMS

April 1997

No Data

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Aerosol Optical Thickness (0.38 µm)


Radiance and polarization measurements from polder
Radiance and Polarization Measurements from POLDER Space

R = 0.865 µm

G = 0.670 µm

B = 0.443 µm

Western Europe

March 10, 1997

Polarization

Radiance


Aerosol optical thickness2
Aerosol Optical Thickness Space

POLDER

April 1997

No Data

0.0

0.1

0.2

0.3

0.4

0.5

Aerosol Optical Thickness (0.865 µm)


Ngstr m exponent
Ångström Exponent Space

POLDER

April 1997

No Retrieval

No Data

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Angstrom Exponent


Aerosol optical thickness3
Aerosol Optical Thickness Space

OCTS

April 1997

No Data

0.0

0.1

0.2

0.3

0.4

0.5

Aerosol Optical Thickness (0.500 µm)


Ngstr m exponent1
Ångström Exponent Space

OCTS

April 1997

No Retrieval

No Data

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Angstrom Exponent


Aerosol optical thickness4
Aerosol Optical Thickness Space

MODIS

April 19, 2000


Aerosol optical thickness5
Aerosol Optical Thickness Space

0

20

40

60

80

100

Fraction of Aerosol Retrievals for 150 days


Global distribution of aeronet stations august 2000
Global Distribution of AERONET Stations—August 2000 Space

  • Automatic recording and transmitting Sun/Sky Photometers

  • Data Base: Aerosol optical thickness, size distribution, phase function & precipitable water

  • Collaborative: NASA – instruments/sites and centralized calibration & database

  • Non-NASA – instruments/sites


TARFOX Space

Atlantic Ocean (July 1996)

0.6

0.5

0.4

0.3

Retrieved optical thickness

0.2

0.1

l = 0.55 µm

0.0

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Sunphotometer optical thickness

0.0


SCAR-B Space

Brazil (August-September 1995)

2.5

Forest

2.0

1.5

Retrieved optical thickness

1.0

Cerrado

0.5

l = 0.66 µm

0.0

0.0

0.5

1.0

1.5

2.0

2.5

Sunphotometer optical thickness


Summary and conclusions
Summary and Conclusions Space

  • Tropospheric aerosols have been ‘rediscovered’ as a major influence on the radiation balance of the Earth, with a potentially large mitigating influence on greenhouse forcing

  • In the past we have been largely forced to use uncalibrated sensors or wide field-of-view ultraviolet spectrometers not specifically designed for the remote sensing of tropospheric aerosol properties

  • Since 1996, with the launch of OCTS and POLDER on ADEOS, we have entered a new era of quantitative remote sensing of tropospheric aerosol from space

  • With the launch of EOS, Envisat-1, and ADEOS II, we will have an unprecedented array of spaceborne sensors with unique characteristics that will enable quantitative aerosol observations on a global scale

    • Enhanced onboard calibration

    • Use of deep space and lunar maneuvers for calibration and sensor degradation analysis

    • Vigorous vicarious calibration using ground-based and airborne sensors

    • Narrow spectral bands that avoid molecular absorption bands

    • Multispectral and multiangle observations

    • Polarization


Summary and conclusions1
Summary and Conclusions Space

  • These spaceborne sensors, when coupled with the AERONET network of sun/sky radiometers for the validation of satellite data, derivation of aerosol models, and statistical characterization of aerosol in remote pristine environments, should enable a much improved analysis of aerosol forcing of the Earth-atmosphere-ocean system

  • The next advance from space is monostatic lidar that will make it possible to characterize the vertical distribution of tropospheric aerosols and clouds that, when coupled with multispectral and multiangular radiometry, will advance the state of our knowledge of how aerosols interact with the Earth and its atmosphere

    • GLAS (December 2001)

    • PICASSO-CENA (February 2003)


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