FIRE IMPACT ON SURFACE ALBEDO SEASONAL CYCLE Yves
FIRE IMPACT ON SURFACE ALBEDO SEASONAL CYCLE Yves Govaerts
METEOSAT INSTRUMENT CHARACTERISTICS Channels Visible (VIS) Water Vapour Infrared : 0. 4 - 1. 0 m : 5. 7 - 7. 1 m : 10. 5 - 12. 5 m 2 VIS detectors Image repeat cycle : 30 min
METEOSAT SURFACE ALBEDO Surface albedo definition Directional Hemispherical Reflectance (DHR) BRF: Bidirectional Reflectance Factor Satellite observation Space borne sensors sample BRFs !
The METEOSAT measurements Sensor Slot n+2 Slot n+3 Slot n+1 Slot n Absorbing atmosphere Scattering atmosphere Anisotropic surface Slot n+
METEOSAT as a Virtual Multi-angle sensor Assumptions Reciprocity principle Sensor Slot n+2 Slot n+3 Slot n+1 Slot n Absorbing atmosphere Slot n+ • Atmosphere is composed of one absorbing gas layer and one scattering layer • US 62 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 Parameters Model : • ozone (TOMS) • Total column water vapour (ECMWF) Scattering atmosphere Anisotropic surface Retrieved : • Equivalent aerosol optical thickness (1) • surface anisotropy (3) One final product is generated every 10 days in order to minimise the cloud effects.
METEOSAT SURFACE ALBEDO PROCESSED AREA(S)
APPLICATIONS 1996 Early Januray 0. 0 Early March 0. 3 0. 6 Early April Pinty, B. , et al. (2000) Surface albedo retrieval from Meteosat: Part 2: Applications, Journal of Geophysical Research, 105, 18113 -18134.
APPLICATIONS SURFACE ALBEDO SEASONAL DYNAMICS Surface albedo change in the Meteosat VIS band as a function of the vegetation amount over different soil types. Monsoon-induced cycle of surface albedo Pinty, B. et al. (2000) Do Human-induced Fires Affect the Earth Surface reflectance at Continental Scales? , EOS Transactions of the AGU, 81, 381 -389.
SURFACE ALBEDO CHANGE MECHANISM Dry season DAYS OF 1996 Dry season
SURFACE ALBEDO CHANGE MECHANISM Decrease Increase Change from November to January 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, 381 -389. Change from January to April Human perturbed cycle
FIRE IMPACT ON SURFACE ALBEDO North Hemisphere Fire-induced perturbation Dry season DAYS OF 1996 Vegetation re-growth
FIRE IMPACT ON SURFACE ALBEDO North Hemisphere Fire-induced perturbation Dry season DAYS OF 1996 Vegetation re-growth
FIRE IMPACT IDENTIFICATION The probability of a fire-induced surface albedo perturbation is estimated with a combination of 3 tests 3 Low albedo values resulting from a decrease High albedo values 1 Low albedo values DAYS OF 1996 2 Probability of dark (burnt) surface
FIRE IMPACT IDENTIFICATION Probability of fire-induced surface albedo perturbation South Hemisphere North Hemisphere
FIRE IMPACT IDENTIFICATION Probability of fire-induced surface albedo perturbation South Hemisphere North Hemisphere
FIRE IMPACT EVALUATION : EXPRESSO Number of active fires detected over the EXPRESSO area in November 1996 in each corresponding Meteosat pixel.
FIRE IMPACT EVALUATION : DHR(30) Meteosat Surface Albedo over the EXPRESSO area mid November 1996 Active fires detected with AVHRR
FIRE IMPACT EVALUATION Probability of fire-induced surface albedo perturbation over the EXPRESSO area November 1996
FIRE IMPACT EVALUATION Burned area map based on AVHRR data over the EXPRESSO region in November 1996 WHEN? Active fires detected with AVHRR
FIRE IMPACT EVALUATION Comparison with the AVHRR-based burned area map
FIRE IMPACT EVALUATION Correlation with the number of active fires detected with AVHRR Percentage of burned pixel (AVHRR) Probability of fire-induced perturbation
Probability of fire-induced surface albedo perturbation over the EXPRESSO area
1996 Prototype Unprocessed pixels due to clouds
2000
2001
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