FOREST FIRE IMPACT ON AIR QUALITY

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FOREST FIRE IMPACT ON AIR QUALITY THE
LANCON-DE-PROVENCE 2005 CASE
S. Strada, C. Mari Laboratoire d'Aérologie,
Université de Toulouse, CNRS, Toulouse,
France J.B. Fillipi, F. Bosseur SPE, Università
di Corsica, CNRS, Corte, France
8th Symposium on Fire and Forest Meteorology
Kalispell,
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Forest Fire and Air Quality A brief introduction
Forest Fires in mediterranean region More
frequent ignition Widening of areas at risk Air
pollution alerts Coupled Atmosphere-Wildfire
Modeling Meso-NH ForeFire To investigate fire
dynamics and chemistry and atmospheric
feedbacks A case study Lançon-de-Provence
(France) 2005 A typical mediterranean wildfire in
a complex topography
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Atmospheric model Meso-NH
Version 4_7_4

• Activated schemes
• Microphysics ICE3
• Turbulence 1D 3D (200m)?
• Advection PPM
• Surface ISBA
• Chemical scheme with 40 chemical species and 73
  chemical reactions (Relacs)?

• Configuration
• Two-way grid nesting 25km, 5km, 1km, 200m
• ECMWF reanalysis
• 72 levels up to 23 km
• dx 40 m near the surface, dx 600 m at
  the top

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Fire Spread Model ForeFire

• Model features
• Analytical formulation of RoS
• Front tracking algorithm

• Coupled Atmosphere-Fire Modeling
• Fire as subgrid scale process
• One-way coupling through ISBA scheme
• Radiative temperature, heating and water vapor
  fluxes as inputs for Meso-NH at each model
  timestep

-gt fraction of area burnt provided by
Forefire -gt gridded through the PGD program
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The Lançon-de-Provence case study
Fire features Date July 1, 2005 Time 0940 LT
-gt 1740 LT On fire 626 ha of scrublands
(garrigue)? In danger downwind inhabited areas
and cultivated lands
A typical meteorological situation the
Mistral Strong northwesterly wind favoured by a
strong pressure gradient over Western Europe and
a tunnel orographic effect
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Fire impact on atmospheric dynamics
Fire vs. no fire simulation at dx1 km
Wind speed difference at the surface (m/s)
Fire tracer _at_ 500 m
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Fire impact on ozone chemistry
Emissions Ei EFi x ?x B x ? Efi Emission
factors g/kg ? Glocal burning
efficiency B Fuel load (kg/m2)
? burnt area (m2)?
Forefire !

Fire vs. background concentrations at dx1 km
NO2fire - NO2background _at_ 500 m
O3fire O3background _at_ 500 m
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Conclusions
Sensitivity of the dynamics and tracer transport
to the coupling -gt fire-induced surface winds -gt
fire emissions injection height particularly
sensitive to fire heat fluxes latent
sensible Effective fire impact several hundreds
of kilometers downwind of the burnt area Well
marked chemical plume with high concentrations of
CO, NOx, VOCs and a contrasted ozone signature
near and downwind of the fire
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Perspectives
Work in progress on simulation with the coupled
model at 200 m resolution (IDRIS -
Vargas)? Comparison with ASQA database Refine
emission factors for the mediterranean ecosystems
(LA SPE) On-line implementation in
ISBA? Test the EDKF scheme on the same
case. Two-way coupling Meso-NH Forefire (ANR
IDEA)?