fire impact on surface albedo seasonal cycle

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