POLDER1, 2

1
POLDER-1, 2 3 Land Surface Applications

• Roselyne Lacaze POSTEL Service Center,
  Medias-France
• with
• F.M. Bréon LSCE/CEA
• J.L. Deuzé LOA
• F. Parol LOA
• C. Proy - Cnes
• J.L. Roujean CNRM/Météo-France

2
Overview

• Overview
• POLDER Saga
• POLDER specificities
• Thematics and Objectives
• Aerosols
• Earth Radiation Budget
• Ocean Color
• Land Surface Applications
• Conclusions

3
Overview of POLDER Saga

• POLDER-1 onboard the ADEOS-1 platform
  (1996-1997). Solar panel failure terminated
  operations (8 months of continuous acquisition)
• POLDER-2 onboard the ADEOS-2 platform (2003).
  Solar panel failure terminated operations (7
  months of continuous acquisition)
• POLDER-3 onboard the PARASOL micro-satellite.
  Fly in formation with the Aqua Train.
  Near-continuous acquisition since March 2005 (1
  year worth of data)

4
POLDER Specificities

• 8 spectral bands from 440nm to 910nm
• 3 Polarized bands 443 (490) 670, 865nm
• Spatial Resolution 6 km
• Bi-dimensional CCD matrix
• Long axis cross-track for POLDER-1 2
• Long axis along track for POLDER-3

5
Thematic - Aerosols

• Objectives determine the physical and optical
  properties of aerosols so as to classify them and
  study their variability and cycle, and quantify
  their influence on Earth's radiation budget.
• Products
• Over Ocean
• total and small particles AOT
• non sphericity index
• Angström coefficient
• effective radius and
  
  refractive index of
  small
  
  particles
• refractive index of large
  
  spherical particles
• Over Land
• AOT of small particles
• Angström coefficient of small particles
• Access POLDER Distribution Center
  http//polder.cnes.fr

J.L. Deuzé, LOA
6
Thematic Earth Radiation Budget

• Objectives improve the climatological
  description of clouds properties, determine the
  atmospheric water vapor content, and quantify the
  influence of clouds on Earth's radiation budget.
• Products
• Cloud cover and cloud phase
• Cloud optical thickness and
  albedo
• SW albedo
• Cloud pressures from oxygen
  absorption and
  from Rayleigh
  scattering
• Water vapor integrated content
• Access POLDER Distribution Center
  http//polder.cnes.f
  r

F. Parol, LOA
7
Thematics Ocean Color

• Objectives understand and quantify the
  biochemical role of the ocean in the global
  carbon cycle.
• Products
• Chlorophyll concentration
• Bio-optical parameters
• Absorption particles
  
  coefficient
• Backscattering particles
  
  coefficient
• Access POLDER Distribution Center
  http//polder.cnes.fr

8
Land Surface Applications

• Overview
• Land Surface quantify the role of
  photosynthesis from the continental biosphere in
  the global carbon cycle.
• Level 2 Algorithms and Products
• Level 3 Algorithms and Products
• Conclusions

9
Land Surface Level 2 Algorithms

• Cloud detection
• apparent pressure in
  
  02 band
• threshold on blue
  
  channel reflectance
• directional variability
• polarized rainbow
• Atmospheric correction
• specified by LSCE

10
Land Surface Level 2 Products

• 2 BRDF Databases
• Selection by month, GLC_2000 biome, NDVI,
  latitude
• POLDER-1 24,857 brdfs
• POLDER-2 24,090 brdfs
• An analysis tool visu_BRDF
• Use of BRDF Databases
• Analysis of Hot Spot signature
• Inter-comparison of BRDF models
• Access POSTEL Service Center http//postel.medias
  france.org/

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Examples of BRDF - 1

• http//postel.mediasfrance.org

12
Examples of BRDFs - 2

• http//postel.mediasfrance.org

13
An analysis tool visu_BRDF
F.M. Bréon, LSCE

• Selection of targets according to biome,
  month, NDVI
• Fit to several analytical models
• Visualization of BRDFs and goodness of
  fit

http//postel.mediasfrance.org
14
Measurements and Analysis of HotSpot
F.M. Bréon, LSCE

• First (and only) quantitative measurement of the
  Hot-Spot (amplitude and shape)
• Analytical model that relates HS (?0) width to
  the ratio of leaf size and density
• Reflectance varies as (1 ?/?0) 1
• A statistical analysis lead to typical
  directional signatures for each biome
• Half width ?0 between 1and 3.

Bréon FM et al., JGR, 2002 Grant I et al, IJRS,
2003
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Validate and rank BRDF models

• The HS signature introduced in the Ross-Li
  analytical model allows the best fit to the
  observed BRDFs

The Ross-Li-HotSpot model is implemented in the
POLDER operational processing line.
Maignan et al., RSE, 2004 Bacour and Bréon, RSE,
2005
16
Level 3 Algorithms POLDER -1 2

• Filtering module
• Normalisation
• model Ross-Li-HotSpot
• specified by LSCE
• Albedo
• directional integration specified by LSCE
• validation by CNRM
• LAI and FCover
• validation by POSTEL

17
Level 3 Algorithms POLDER-3

• Same as POLDER-1 2
• Filtering module
• Normalisation
• Directional integration for albedo retrieval
• Changes
• Broadband albedo specified by CNRM
• FAPAR retrieval
• Roujean et Bréon, 1995.
• Validation by Inra
• No LAI, No FCover

18
Level 3 products Albedo

• POLDER-1 2 Albedo validated by
  CNRM/Météo-France
• Better than operational climate model
  albedos
  (ECMWF, Arpège, ISCCP), and
  satellite products
  (MISR, METEOSAT)
• More consistent than MODIS albedos
• Seasonal trend
• MODIS slighty lower the geometric
  
  component contributes negatively to
  
  the total reflectance because of
  
  constraint on directional coefficient
• Report available
  http//postel.mediasfrance.org
  /

J.L. Roujean, CNRM
19
Level 3 Products - Albedo

• POLDER-3 / PARASOL Albedo
• Validation will be performed by CNRM
• Comparison with satellite products
  LSA SAF
  albedo from MSG,
  and MODIS
• Comparison with in-situ data
  
  BSRN, etc

Black Sky albedo, July 2005
Products available at http//postel.mediasfrance.o
rg/
20
Conclusions

• Overview
• Land Surface Applications
• Conclusions
• POLDER-3 / PARASOL re-processing schedule
• Next algorithmic developments
• Lessons learnt

21
POLDER-3 / PARASOL schedule

• September 2006
• Cnes starts the Level 1 reprocessing with updated
  calibration coefficients
• November 2006
• The POSTEL Service Center starts the Level 2 and
  Level 3 reprocessing
• New cloud detection (threshold on blue channel
  reflectance updated)
• New albedo definition (new spectral conversion
  coefficients)
• End of 2006 Availability through POSTEL Service
  Center website (http//postel.mediasfrance.org)
• 18 months of POLDER-3 / PARASOL products (Albedo,
  NDVI, FAPAR)
• POLDER-3 / PARASOL BRDF Database

22
Algorithmic Developments

• Aerosol retrieval over land
• Use of polarized reflectances
• Method sensitive to the small particles
  (polarizing aerosols)
• Very good consistency between retrievals over
  land and ocean
• Good agreement with AERONET measurements

23
Conclusions

• Large improvements in aerosol and cloud
  properties retreival thanks to multi-directionalit
  y and polarization
• Land Surfaces
• improvement in albedo assessment thanks to
  multi-directionality
• great potential of information in BRDF
• no success to exploit this potential to improve
  LAI/FCover assessment
• spatial resolution (6km) is a great limitation
• Future multi-directional sensor mission not
  foreseen