FIRE IMPACT ON SURFACE ALBEDOSEASONAL CYCLE
Yves Govaerts
METEOSAT INSTRUMENT CHARACTERISTICS
ChannelsVisible (VIS) : 0.4 - 1.0 mWater Vapour : 5.7 - 7.1 mInfrared : 10.5 - 12.5 m
Image repeat cycle : 30 min
2 VIS detectors
METEOSAT SURFACE ALBEDO
Surface albedo definitionDirectional Hemispherical Reflectance (DHR)
'''0
2
00 ,1
, dzBRFZDHR
BRF: Bidirectional Reflectance Factor
Space borne sensors sample BRFs !
Satellite observation
The METEOSAT measurements
Anisotropic surface
Absorbing atmosphere
Slot nSlot n+1
Slot n+2 Slot n+3
Slot n+
Sensor
Scattering atmosphere
METEOSAT as a Virtual Multi-angle sensor
Slot nSlot n+1
Slot n+2 Slot n+3
Slot n+
Sensor
Anisotropic surface
Reciprocity principle
Sensor SensorSensor
Absorbing atmosphere
Scattering atmosphere
Model :•ozone (TOMS)•Total column water vapour (ECMWF)
Parameters
Retrieved :•Equivalent aerosol optical thickness (1)
•surface anisotropy (3)
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
One final product is generated every 10 days in order to minimise the cloud effects.
PROCESSED AREA(S)
METEOSAT SURFACE ALBEDO
APPLICATIONS
Early Januray
1996
Early March
Early April
0.0
0.6
0.3
Pinty, B., et al. (2000) Surface albedo retrieval from Meteosat: Part 2: Applications, Journal of Geophysical Research, 105, 18113-18134.
APPLICATIONS
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.
SURFACE ALBEDO SEASONAL DYNAMICS
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 Dry seasonDAYS OF 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 November to January Change from January to April
Decrease Increase
SURFACE ALBEDO CHANGE MECHANISM
Active fire for December 1996
Human perturbed cycle
DAYS OF 1996
FIRE IMPACT ON SURFACE ALBEDO
Dry season
Fire-inducedperturbation
Dry season
North Hemisphere
Vegetation re-growth
DAYS OF 1996
FIRE IMPACT ON SURFACE ALBEDO
Dry season
Fire-inducedperturbation
Dry season
North Hemisphere
Vegetation re-growth
FIRE IMPACT IDENTIFICATION
Low albedovalues
High albedovalues
1
The probability of a fire-induced surface albedo perturbation is estimated with a combination of 3 tests
Probability of dark(burnt) surface
2
Low albedovalues resultingfrom a decrease
3
DAYS OF 1996
FIRE IMPACT IDENTIFICATION
South Hemisphere North Hemisphere
Probability of fire-induced surface albedo perturbation
FIRE IMPACT IDENTIFICATION
South Hemisphere North Hemisphere
Probability of fire-induced surface albedo perturbation
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
Active fires detected with AVHRR
Burned area map based on AVHRR data over the EXPRESSO region in November 1996
WHEN?
FIRE IMPACT EVALUATION
Comparison with the AVHRR-based burned area map
FIRE IMPACT EVALUATION
Probability of fire-induced perturbationPercentage of burned pixel (AVHRR)
Correlation with the number of active fires detected with AVHRR
Probability of fire-induced surface albedo perturbation over the EXPRESSO area
1996Prototype
Unprocessedpixels due to clouds
2000
2001