1. FIRE IMPACT ON SURFACE ALBEDO
SEASONAL CYCLE
Yves Govaerts

2. METEOSAT INSTRUMENT CHARACTERISTICS
Channels
Visible (VIS) : m
Water Vapour : m
Infrared : m
2 VIS detectors
Image repeat cycle : 30 min

3. METEOSAT SURFACE ALBEDO Surface albedo definition
Directional Hemispherical Reflectance (DHR)
BRF: Bidirectional Reflectance Factor
Space borne sensors sample BRFs !
Satellite observation

5. The METEOSAT measurements
Absorbing atmosphere
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Sensor
Scattering atmosphere
Anisotropic surface

6. METEOSAT as a Virtual Multi-angle sensor Reciprocity principle
Assumptions
Atmosphere is composed of one absorbing gas layer and one scattering layer
US62 atmospheric profile
Continental aerosol type
Atmospheric and surface scattering properties are constant along the day
Surface scattering properties can be represented by the RPV BRF model
Sensor
Sensor
Sensor
Sensor
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Absorbing atmosphere
Parameters
Model :
ozone (TOMS)
Total column water vapour (ECMWF)
Scattering atmosphere
Retrieved :
Equivalent aerosol optical thickness (1)
surface anisotropy (3)
One final product is generated every 10 days in order to minimise the cloud effects.
Anisotropic surface

7. METEOSAT SURFACE ALBEDO
PROCESSED AREA(S)

8. APPLICATIONS 1996 Early Januray Early March Early April 0.0 0.3 0.6
Pinty, B., et al. (2000) Surface albedo retrieval from Meteosat: Part 2: Applications, Journal of Geophysical Research, 105,

9. Monsoon-induced cycle of surface albedo
APPLICATIONS
SURFACE ALBEDO SEASONAL DYNAMICS
Monsoon-induced cycle of surface albedo
Surface albedo change in the Meteosat VIS band as a function of the vegetation amount over different soil types.
Pinty, B.et al. (2000) Do Human-induced Fires Affect the Earth Surface reflectance at Continental Scales?, EOS Transactions of the AGU, 81,

11. SURFACE ALBEDO CHANGE MECHANISM
Dry season
Dry season
DAYS OF 1996

12. SURFACE ALBEDO CHANGE MECHANISM
Decrease
Increase
Change from November to January
Change from January to April
Human perturbed
cycle
Active fire for December 1996
Pinty, B., Verstraete, M.M., Gobron, N., Govaerts, Y., and Roveda, F. (2000) Do Human-induced Fires Affect the Earth Surface reflectance at Continental Scales?, EOS transactions of the AGU, 81,

13. FIRE IMPACT ON SURFACE ALBEDO
North Hemisphere
Fire-induced
perturbation
Dry season
Dry season
Vegetation re-growth
DAYS OF 1996

14. FIRE IMPACT ON SURFACE ALBEDO
North Hemisphere
Fire-induced
perturbation
Dry season
Dry season
Vegetation re-growth
DAYS OF 1996

15. FIRE IMPACT IDENTIFICATION
The probability of a fire-induced surface albedo perturbation is estimated with a combination of 3 tests
Low albedo
values resulting
from a decrease 3
Low albedo
values
High albedo 1
Probability of dark
(burnt) surface 2
DAYS OF 1996

16. FIRE IMPACT IDENTIFICATION
Probability of fire-induced surface albedo perturbation
South Hemisphere
North Hemisphere

17. FIRE IMPACT IDENTIFICATION
Probability of fire-induced surface albedo perturbation
South Hemisphere
North Hemisphere

18. FIRE IMPACT EVALUATION : EXPRESSO
Number of active fires detected over the EXPRESSO area
in November 1996 in each corresponding Meteosat pixel.

19. FIRE IMPACT EVALUATION : DHR(30)
Meteosat Surface Albedo over the EXPRESSO area mid November 1996
Active fires detected with AVHRR

20. FIRE IMPACT EVALUATION
Probability of fire-induced surface albedo perturbation
over the EXPRESSO area November 1996

21. FIRE IMPACT EVALUATION
Burned area map based on AVHRR data over the EXPRESSO region in November 1996
Active fires detected with AVHRR
WHEN?

22. FIRE IMPACT EVALUATION
Comparison with the AVHRR-based burned area map

23. FIRE IMPACT EVALUATION
Correlation with the number of active fires detected with AVHRR
Percentage of burned pixel (AVHRR)
Probability of fire-induced perturbation

24. Probability of fire-induced surface albedo perturbation
over the EXPRESSO area

25. 1996
Prototype
Unprocessed
pixels due to
clouds

26. 2000

27. 2001