Analysis of satellite imagery to map burned areas in Sub-Saharan Africa

CARBOAFRICA conference “Africa and Carbon Cycle: the CarboAfrica project”Accra (Ghana) 25-27 November 2008

Ilaria Palumbo, Heiko Balzter, Kevin TanseyDepartment of Geography, University of Leicester, UKemail: ip53@le.ac.uk

Vegetation index (green) and fire dynamics in Africa in the year 2001 seen from satellite.

Source: NASA http://landdb1.nascom.nasa.gov/animation/images/Africa_Fire_NDVI_2001.gif

Fire activity in Africa

• derive estimations of fire emissions;• information about the extent;• information about the temporal occurrence;• information about the intensity of burning;

Why mapping Why mapping burned burned areasareas??

• GBA2000 SPOT-VGT images, 1km; • Globscar ATSR-2, 1km;• Globcarbon VGT, (A)ATSR and MERIS, 1km;• L3JRC SPOT-VGT images, 1km - 7 years;• MCD45 MODIS, 500m - since 2002;• others;

Products availableProducts available

• global level coverage since the 1990s, 1km spatial resolution;• dual view – nadir & forward; • possible Aerosol Optical Depth retrieval and correction;

the AATSR imagerythe AATSR imagery

Can we use AATSR for burned area mapping?

• run model for the AOD retrieval; • derive surface reflectance @1km;• use the corrected reflectance for burned area mapping;

Processing AATSR dataProcessing AATSR data

AOD aerosol optical depth

TOA, VZA, SZA, lat, lon, cloud flags

AATSR data

extract parameters

LUT cont.

LUT ocean

LUT urban

LUT dust LUT smoke

INVERSION

Rsurf, τcont, E Rsurf, τocean, E Rsurf, τurban, E Rsurf, τdust, E Rsurf, τsmoke, E

select Best-fit τ

select ‘best’ RsurfTOA: Top Of the Atmosphere

Processing AATSR dataProcessing AATSR data

Results Results corrected surface reflectance

1-10th July 2003

RGB: 1600, 870, 670 nm

Results Results

period 1st-10h July 2003RGB: 1600, 870, 550 nm

…and problems

Can we use AATSR for burned area Can we use AATSR for burned area mapping?mapping?

maybe not at continental level…

some potentials exist though

corrected surface reflectance

2nd August 20027.51am

RGB: 1600, 870, 550 nmAATSR

MODIS/Terra - 500m

AATSR - 1km

Comparison AATSR/MODISComparison AATSR/MODIS

2002-08-24 2002-08-2

MODIS bMODIS burned area product urned area product

MODIS vs AATSR

• higher spatial resolution (500m);• better spatial coverage of the study area,

limited missing data;• validated using ETM+ scenes over southern

Africa;• information about quality assessment is

provided.

MODIS MCD45A1 bMODIS MCD45A1 burned area product urned area product

MONTHLY BURNED AREA MAPS

BA Month123456789101112

Use MODIS product for further analysis Use MODIS product for further analysis • extract burned area info per vegetation

class;• derive fire emissions at continental and

country level;• analysis of the climate-human-fire

interactions;

MCD45A1 burned areas

Globcover

ConclusionsConclusions• the aerosol corrected ATSR series reflectance

can be used to map burned area at regional level and before year 2000;

• the improved spatial resolution and more frequent coverage of the MODIS product is better suited to the needs of CARBOAFRICA;

• a reliable burned area map is needed to derive accurate emissions from fires.

thank you !