g. roberts, m. j. wooster and g. perry department of geography, king’s college london fire...
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G. Roberts, M. J. Wooster and G. PerryG. Roberts, M. J. Wooster and G. PerryDepartment of Geography, King’s College LondonDepartment of Geography, King’s College London
Fire Radiative Energy:Fire Radiative Energy:Ground and Satellite ObservationsGround and Satellite Observations
Geostationary Fire Monitoring Applications WorkshopMarch 23-25, 2004, EUMETSAT
Remote Sensing Fire Radiative Energy (FRE)Remote Sensing Fire Radiative Energy (FRE)
• Interested in FRE from SEVERI :
• Can be used to estimate rates and total amounts of biomass combusted using observations of emitted thermal energy released during vegetation fires
• This then acts as the basis for carbon and trace gas/aerosol emissions inventories
Fire Radiative Energy vs. Mass CombustedFire Radiative Energy vs. Mass Combusted
• Very good relationship – FRE well related to mass combusted
• BUT only ~ 2000 KJ radiated per kg burnt
• Net heat yield quoted at ~ 16,000 KJ/kg • 15 ± 7 % of theoretically released energy appears to be actually radiated
R2 = 0.964
FRE Derivation in the MIRFRE Derivation in the MIR
hMIRMIR
samplMIR L
a
AFRE ,.
..
•FRE derived as a function of MIR spectral radiance:
Advantages :• Linear
• computationally efficient• alterations can be applied later
• e.g. atmospheric correction • One spectral channel
• not sensor specific
Algorithm :• active fire detection and background characterisation• FRE derived per pixel and per fire
LMIR,h = ‘fire’ pixel MIR spectral radiance
MIR = ‘fire’ pixel MIR emissivity
a = constant from Planck fn approx.Asampl = ground-pixel area (m²)
SEVERI and MODIS
SEVERI (12:57 – Sept 1st 2003) MODIS (12:20 – Sept 1st 2003)
Green : MIR channelYellow : Detected active fires
SEVERI MIR saturationSaturation point
Initial detection
Daytime: Fires detectable down to ~ 0.5 to 1.0 hectares (assume 800 K)Nighttime: Somewhat smaller (maybe to ½ this size)
BUT SOME QUESTIONS REMAIN……….
• Do ground-based and spaceborne FRE agree ?
• Do very large fires have similar % of energy released as radiation?
• Cloud cover problem• coupling FRE & burned area products ?• fit a model to available samples or interpolation ?
• Active fire detection• Couple temporal and spatial domains
• Background characterisation• Fire detection
Acknowledgements
Thanks to :
• Rothamsted Agricultural Research• Botswana Wildlife Service• DLR• EUMETSAT• NASA• Staff and students at Kings/UCL
Current Approaches to Emission Current Approaches to Emission Inventory• Based on estimates of total biomass combusted (M)
– converted into emissions estimate via ‘emissions factors’
Biomass = Burnt * Biomass * Burning Burnt (M) Area Density Efficiency
• Difficulty reliably estimating biomass density & burning efficiency – uncertainty propagates through to estimates of M
• Andreae and Merlet (2001) demonstrate order-of-magnitude difference between fire frequency and EO-approaches and suggest a new route maybe needed to enhance the existing methodologies.