Aerosol optical thickness retrieval over land and water using SCIAMACHYGOME data

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Aerosol optical thickness retrieval over land and
waterusing SCIAMACHY/GOME data

• J. Kusmierczyk-Michulec
• G. de Leeuw

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The SCanning Imaging Absorption SpectroMeter for
Atmospheric CHartographY (SCIAMACHY) on board
the ESA Envisat satellite

• launched in March 2002
• high-resolution (0.2-0.4 nm) spectrometer
• wavelength range 240--2380 nm
• Swath Dim. 960 km (cross track) by
• 25 km (along track at
  nadir)
• Nadir scan 4 pixels of 240 km (cross track)
  by 25 km (along track)
• Limb scan 960 km (cross track) vertical
  tangential step size 3.0 km

http//envisat.esa.int/
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The Global Ozone Monitoring Experiment (GOME)

• Launched in April 1995
• 4-channel grating spectrometer
• Spectral resolution 0.2-0.4 nm
• Wavelength range 240 -790 nm
• One across-track 3 ground pixels 40 km x 320 km

GOME aboard ERS-2 (courtesy of ESA)
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Aerosol retrieval algorithm for SCIAMACHY/GOME
where ?atm ?R ?a ?aR ?s is the zenith
solar angle ?? is the zenith observation angle
?s -?? is the relative azimuth between the
incident and observation vertical
planes
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TOA reflectance - example

• Ra is based on the sunphotometer
• measurements in Ispra (03.06.98)
• (Holben et al. 1998)
• Rtoa - GOME data

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Spectral reflectances of natural surfaces
-examples
LER-Lambertian Equivalent Reflectance derived
from reflectances measured by GOME (R.
Koelemeijer et al., 2003)
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Approach over land/water for GOME
Reflectances at TOA measured by GOME (380, 440,
463, 495, 555, 670 nm)
LUT of aerosol/atmospheric/Rayleigh
reflectances for a given satellite and solar
geometry 3 predominantly aerosol
types -maritime, lt-0.1, 0.65gt - continental,
lt0.65, 1,32gt - urban, lt1.32, 2.8gt
Cloud screening FRESCO algorithm (Koelemijer et
al., 2001,2002)
Correction for ozone absorption
The best fit with aerosol model
Surface correction GOME surface reflectances
database
AOD
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Validation
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Validation
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Validation
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Validation
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Validation
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Validation
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Validation
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Validation
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Validation
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Outline
Aerosol optical thickness, winter 1997
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Aerosol optical thickness, winter 2000
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Aerosol optical thickness, summer 1997
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Aerosol optical thickness, summer 2000
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Aerosol optical thickness, spring/autumn 1997
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Aerosol optical thickness, spring/autumn 2000
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Acknowledgments

• We thank the PI investigators Didier Tanré,
  Brent Holben, Philippe Goloub and Giuseppe
  Zibordi, and their staff for establishing and
  maintaining the AERONET sites used in this
  investigation.
• We acknowledge Piet Stammes and Martin de Graaf
  for kindly providing us GOME data and the results
  from FRESCO algorithm.
• The algorithm was developed as part of the EO-037
  project of the National Data User Support Program
  of the Netherlands Space Research Organization
  (SRON).

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Illustration of the retrieval process- example 1
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Illustration of the retrieval process example 2
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Illustration of the retrieval process example 3
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Contribution of the surface to TOA reflectance