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Fire Radiative Energy: Ground and Satellite Observations

Fire Radiative Energy: Ground and Satellite Observations. G. Roberts, M. J. Wooster and G. Perry Department of Geography, King’s College London. Geostationary Fire Monitoring Applications Workshop March 23-25, 2004, EUMETSAT. Remote Sensing Fire Radiative Energy (FRE).

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Fire Radiative Energy: Ground and Satellite Observations

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  1. Fire Radiative Energy:Ground and Satellite Observations G. Roberts, M. J. Wooster and G. Perry Department of Geography, King’s College London Geostationary Fire Monitoring Applications Workshop March 23-25, 2004, EUMETSAT

  2. 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

  3. Spectrometer video UK Fieldwork 12 m tower MIR camera Mini Met Station Fuel Bed Digital Scales

  4. FRE inter-comparison: MIR camera vs spectroradiometer Spectroradiometer MIR camera

  5. Rate of FRE Release vs Rate of Mass Loss Increasing Time

  6. Fire 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

  7. FRE Derivation in the MIR • FRE derived as a function of MIR spectral radiance: LMIR,h = ‘fire’ pixel MIR spectral radiance MIR = ‘fire’ pixel MIR emissivity a = constant from Planck fn approx. Asampl = ground-pixel area (m²) • Algorithm : • active fire detection and background characterisation • FRE derived per pixel and per fire • Advantages : • Linear • computationally efficient • alterations can be applied later • e.g. atmospheric correction • One spectral channel • not sensor specific

  8. SEVERI and MODIS SEVERI (12:57 – Sept 1st 2003) MODIS (12:20 – Sept 1st 2003) Green : MIR channel Yellow : Detected active fires

  9. SEVERI and MODIS FRE R2 = 0.74

  10. Total emitted energy (MW) = 500115 (9.7 MW/sec) Total Biomass Combusted (Kg) =250145 (4.9 Kg/sec)

  11. 6am 9pm 12:30pm

  12. SEVERI MIR saturation Saturation 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)

  13. 6am 9pm 12:30pm

  14. 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

  15. Thanks to : • Rothamsted Agricultural Research • Botswana Wildlife Service • DLR • EUMETSAT • NASA • Staff and students at Kings/UCL Acknowledgements

  16. 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.

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