Aerosol distribution over the western Mediterranean basin during a Mistral

event

Salameh T., Drobinski P., Menut L.,

Bessagnet B., Flamant C., Hodzic A., Moulin C., Vautard R.

Scientific motivation Aerosols over the western Mediterranean basin

sources: regional: from western and eastern Europe (e.g. Sciare et al. 2003; Traub et al.

2003; Schneider et al. 2004) and from Saharan desert (e.g. Bergametti et al. 1992; Moulin et al. 1998; Guieu et al. 2002)

linked to large-scale phenomena (Moulin et al. 1997) emissions: urban and industrial, transportation, forest fires, saharan dust, sea… potential impact on precipitation, radiation, air quality and ecosystems

(Lelieveld et al. 2002)

Frequent occurrence of Mistral events (5-15 days/month) pre-conditioned by cyclogenesis over the Gulf of Genoa and the passage of a trough over Europe extend as far as few hundreds of kilometers offshore (Jansa 1987) and advect

pollution over long distances (Corsmeier et al. 2005) associated with low continental pollution (Bastin et al. 2006)

What is the aerosol distribution over the western Mediterranean during a Mistral event?

The March 24, 1998 Mistral event: the dataset

The context: the FETCH experiment Investigation of air/sea exchanges in a coastal environment under strong wind

conditions (Hauser et al. 2003) Special observation period : March 12 to April 15, 1998

March 24, 1998: well documented Mistral event (Flamant et al. 2003)

The dataset Above the Mediterranean Sea

Radiosoundings (launched from the RV Atalante) Airborne measurements (lidar, in-situ measurements) Shipborne in-situ measurements and buoys Satellite data (AMI-Wind/ERS and SeaWifs)

Above the continent Operational meteorological surface stations Operational radiosounding (Lyon, Nîmes, Ajaccio)

Mesoscale dynamical and chemical simulations of the March 24, 1998 Mistral event

MM5 model (Grell et al. 1995) Initial & boundary conditions ERA-40 Three nested domains

43 sigma levels Domain 1: 50x50 points, 27 km Domain 2: 82x82 points, 9 km Domain 3: 58x40 points, 3 km

Chemistry transport model

CHIMERE (Schmidt et al. 2001) 12 vertical levels (surface-500 HPa) EMEP emissions Initial & boundary conditions from LMDZ-INCA (gas) and GOCART

(aerosols)

Aerosol emission sources (EMEP inventory)

NO PPM-coarse particles

SO2 CO

Urban & industrial sources

Ships

+ saharan dusts (not shown)

MM5 quantitative validation: near-surface data

Over the Mediterranean SeaOver the continent

10-m wind and 2-m temperature from the Météo-France meteorological operational network 10-m wind from AMI-Wind

MM5 quantitative validation: vertical profiles

Radiosoundings

Nîmes (continent)

Lyon (continent)

RV Atalante(Mediterranean Sea, Gulf of Lion)

March 24, 1998 synoptic environment

Sheltered region associated with the western Alps wake (gravity wave breaking and wall separation in the western Alps wake, Drobinski et al. 2005)

Ligurian outflow

Mistral

Tramontane

0600 UTC 0900 UTC

1200 UTC 1500 UTC

1800 UTC 2100 UTC

Aerosol distribution over the western Mediterranean basin

Aerosol loading on March 24, 1998

Local emissions from the region of Toulon + aerosol plume transported from northern Italy

Aerosols transported from northern France and channeled in the Rhône valley (Mistral)

Absence of lateral exchanges between the plumes transported by the Mistral and the Ligurian outflow (despite gravity wave breaking and wall separation induced turbulence)

0600 UTC 0900 UTC

1200 UTC 1500 UTC

1800 UTC 2100 UTC

Zoom on the Gulf of Lion (1100 UTC):comparison with SeaWifs imagery

AF, FC and CE: Legs of the ARAT aircraft carrying

LEANDRE-2 lidar

Advection from southwestern and northern France through

the Aude valley (Tramontane)

Advection along the Rhône valley (Mistral) and from

northern Italy (Ligurian outflow)

A

F

C

E

Zoom on the Gulf of Lion (1800 UTC):comparison with LEANDRE 2 Lidar, leg AF

LEANDRE-2 Atmospheric ReflectivityCHIMERE Atmospheric reflectivity

Fos-Berre plume

Aerosol-free region

Long-range transport

Conclusion and perspectives

Conclusion Unsteady event: in addition to the local plumes, the aerosol distribution over

the western Mediterranean is dominated by: the plume transported along the Aude valley by the Tramontane flow during

the morning period the plume from central/northern France channeled within the Rhône valley by

the Mistral, and the plume advected by the Ligurian outflow composed of the industrial and urban emissions from Milano

Over Toulon, the absence of wind in the sheltered area is associated with aerosol stagnation (from local origin and from past Milano plume)

Future prospects Representativity of this case: classification typical aerosol distribution

associated with all typical Mediterranean weather regimes (including Mistral)