radiative transfer modelling for the characterisation of natural burnt surfaces ao/1-5526/07/nl/he...
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Radiative Transfer Modelling for the characterisation of natural burnt surfaces
AO/1-5526/07/NL/HE
Recommendations
P. LEWIS1, T. QUAIFE5, J. GOMEZ-DANS1,2, M. DISNEY1, M. WOOSTER2 , D. ROY3, B. PINTY4
1. NCEO/DEPT. GEOGRAPHY, UNIVERSITY COLLEGE LONDON, GOWER ST., LONDON WC1E 6BT, UK 2. NCEO/DEPT. GEOGRAPHY, KING'S COLLEGE LONDON, STRAND, LONDON WC2R 2LS, UK 3. GEOGRAPHIC INFORMATION SCIENCE CENTER OF EXCELLENCE, SOUTH DAKOTA STATE
UNIVERSITY, WECOTA HALL, BOX 506B, BROOKINGS, SD 57007-3510, USA 4. INSTITUTE FOR ENVIRONMENT AND SUSTAINABILITY (IES), EC JOINT RESEARCH CENTRE, VIA E.
FERMI 1, TP 440, 21020 ISPRA (VA), ITALY
5. NCEO/DEPT. GEOGRAPHY, EXETER UNIVERSITY,
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Overview
EO technology overview (talk 1)– Wildfire detection and quantification– Brief summary of relevant results– ESA and related missions
Modelling fire impacts (talk 2)– Semi-analytical– 3D– Thermal– Linear modelling
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EO technology overview: wildfire
Technologies:– Surface:
Optical (main focus here) Thermal (secondary focus) Microwave
– Atmosphere Not considered here
All technologies rely on spatial and temporal localisation of fire
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Thermal: detection
Detect anomalous high T – Polar orbiting
Don’t view all fires– Orbital convergence
– Some methods night only (lower fire activity) Some methods rely on T saturation
– Geostationary Lower spatial, higher temporal resolution Low resolution at high latitudes
All impacted by cloud
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Optical: detection
Sometimes feasible from single image: classification Mostly use time series Mostly use SWIR (also NIR)
– NBR/NDVI Compounded by BRDF effects
– Mostly considered noise, but can be treated Worse cloud/smoke problems that thermal
– Esp. if shorter wavelengths used Moderate resolution: global
– Polar orbiting (mainly), also geostationary Higher resolution:
– Low revisit used for specific study areas Or use longer time between
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Active microwave: detection
Essentially classification mostly– Time series, generally
Issue of attribution of signal change to fire Complexity from moisture variations
– Not such an issue if materials dry? Complexity from dry materials Huge advantage in areas of high cloud cover
– Tropics
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Fire impact
optical fire severity measures fire radiative energy
– integral over time of fire radiative power ‘direct’ measurements of pre-post biomass
– active microwave– lidar measurements– vegetation indices
area affected by fire from spectral unmixing atmospheric measurement of gasses and particles
released by fire
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Fire detection and impact
Best strategy, combine information– Multiple moderate resolution optical– Constellations of higher resolution– Combined optical and thermal– Combine all sources
Need appropriate theoretical background, models, and algorithms
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Contributions of this study
Model to estimate fcc– bottom-up approach to C release estimate
Needs fuel load
– Compare with FRE Fcc model generic to all optical sensors
– Should be able to combine information– Burn signal results suggest use as constraint– Measure is linear
Simple spatial scaling
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The relevance of the algorithm to the exploitation of data from ESA and related sensors and missions
ENVISAT Earth Explorers Sentinels Meteorological missions Others
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ENVISAT: MERIS
300m, VIS/NIR, many channels Issues:
– No SWIR sampling– Geolocation (?)– BRDF effects not too great
Main route to exploitation:– Detect fire from other sensors– Apply fcc algorithm
Noting issues wrt burn materials/dead vegetation confusion
– Would be aided by easy to use gridded surface reflectance product
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ENVISAT: AATSR
Thermal– Detection (night time saturation or near saturation)
(WFA)– Can’t use for FRE
Optical– Relevant wavelengths– Only 4 wavebands
Issues with 3 parameter model Unless use burn signal constraint
– Dual view possibly interesting for fcc directional effects Same argument for MISR, CHRIS-PROBA
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Earth Explorers
Earthcare: atmsophere (out of scope) – MSI worth considering?
Wind from ADM-Aeolus relevant (out of scope) SMOS soil moisture relevant (fire risk) (out of
scope)
PREMIER: atmosphere (out of scope) BIOMASS
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BIOMASS
P band SAR Real potential for pre-post fire woody biomass
estimates– Would need to demonstrate acceptable
precision in change signal Unlikely viable for dry grass fires
– But distinguishing these of interest
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Sentinels
Sentinel 1– C band SAR– Arguments above, re detection– but saturation at higher biomass
So biomass change issues if pre-fire biomass high
Sentinels 4,5– Atmosphere (out of scope)
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Sentinel 2
13 bands across SW Varying spatial resolution 60m+ Satellite pair
– Increased viewing opportunity– 5 day (cloud free)
‘extended viewing capability’– BRDF issues would need treatment
Fcc product at 60m, or implement multi-scale for further localisation– Need detection algorithms– Very intersting platform to develop fcc-based detection
algorithm
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Sentinel 3
OLCI and SLSTR similar to MERIS/AATSR SLSTR: dedicated low-dynamic range ‘fire’
channels – So FRP & day/night detections
Optical, similar to MERIS/AATSR uses and issues– BUT very interesting combination of
platforms (Sentinel-2,-3) for multi-scale strategy (possibly also then Sentinel-1/BIOMASS)
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Meteo
MetOp– AVHRR instrument
Optical (includes SWIR)– BRDF effects (can be treated: MODIS algorithm prototyped with
AVHRR)– direct value if constrained burn signal used for fcc– Indirect, of value to moderate resolution constellation approach
thermal (fire saturation)
MSG/MTG– Operational FRE– Optical burned area/fcc difficult
Low signal/noise for any by largest fires BUT tracking fcc post fire would be of interest
– Need constraint to burn signal, but probably can get from active fire detections
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Others
Medium resolution (sub 1m to 10s m)– VIS/NIR– SPOT Pléiades, DMC, SEOSAT-INGENIO, RapidEye, EROS
Revisit period for individual may not be high enough, but have constellation missions
Also CEOS LSI-concept – all as virtual constellation Probably most useful for localisation of information if fire known (e.g.
thermal)– Fcc could be applied if constrained burn signal– And atmospheric correction
EnMAP– Very relevant for characterisation of fcc– BRDF effects for off-nadir pointing– Don’t need full hyperspectral for this though
So maybe target more subtle information
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Discussion
3 parameter fcc model– Best used with >> 3 bands– Or strong constraint to burn signal
2 single most interesting sensors– Sentinel-2 / EnMAP– Both aim at high repeat coverage high
resolution
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Discussion
A major limitation to monitoring / characterisation is often viewing opportunity– So should develop multi-sensor concepts– Including multi-resolution– Issues:
different spectral sampling different spatial resolutions potentially different viewing and illumination angles
– Fcc approach can at least partially deal with all of these (BRDF modelling for latter)
– Longer term, may consider full DA system (e.g. ESA EOLDAS) But technology needs development
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Key Recommendations
Fcc should be developed into operational algorithms to quantify fire impact
Method should be generic– needs testing ESA sensors and Sentinel prototypes
Investigate constraint for application to sensors with not >>3 wavebands
Issues in study in comparison of fcc-FRE– Need further investigation
Most application here to S. Africa– Wider application / testing
Develop method for multiple data streams– Including multiple resolutions