FOREST FIRE IMPACT ON AIR QUALITYTHE LANCON-DE-PROVENCE 2005 CASE

S. Strada, C. MariLaboratoire d'Aérologie, Université de Toulouse, CNRS, Toulouse, France

J.B. Fillipi, F. BosseurSPE, Università di Corsica, CNRS, Corte, France

8th Symposium on Fire and Forest Meteorology – Kalispell,

Forest Fire and Air QualityA brief introduction

Forest Fires in mediterranean region

More frequent ignitionWidening of areas at risk

Air pollution alerts

Coupled Atmosphere-Wildfire ModelingMeso-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

Atmospheric model: Meso-NH

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

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)

Fire Spread Model: ForeFire

Model features Analytical formulation of RoS Front tracking algorithm

Coupled Atmosphere-Fire Modeling

Fire as subgrid scale processOne-way coupling through ISBA schemeRadiative temperature, heating and water vapor fluxes as inputs for Meso-NH at each model timestep

-> fraction of area burnt provided by Forefire-> gridded through the PGD program

The Lançon-de-Provence case study

Fire features

Date: July 1, 2005Time: 09:40 LT -> 17:40 LTOn 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

Fire impact on atmospheric dynamicsFire vs. no fire simulation at dx=1 km

Wind speed difference at the surface (m/s)

Fire tracer @ 500 m

Fire impact on ozone chemistry

Fire vs. background concentrations at dx=1 km

Emissions: Ei = EFi x x B x

Efi = Emission factors [g/kg] Glocal burning efficiency B = Fuel load (kg/m2) = burnt area (m2) Forefire !

[NO2]fire - [NO2]background @ 500 m [O3]fire – [O3]background @ 500 m

Conclusions

Sensitivity of the dynamics and tracer transport to the coupling-> fire-induced surface winds-> 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

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)