Aerosol distribution over the western Mediterranean basin during a Mistral event

1
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.

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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?
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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)

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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)

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Aerosol emission sources (EMEP inventory)
saharan dusts (not shown)
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MM5 quantitative validation near-surface data
Over the Mediterranean Sea
Over the continent
10-m wind and 2-m temperature from the
Météo-France meteorological operational network
10-m wind from AMI-Wind
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MM5 quantitative validation vertical profiles
Radiosoundings
Lyon (continent)
Nîmes (continent)
RV Atalante (Mediterranean Sea, Gulf of Lion)
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March 24, 1998 synoptic environment
0900 UTC
0600 UTC
Tramontane
Mistral
Sheltered region associated with the western
Alps wake (gravity wave breaking and wall
separation in the western Alps wake, Drobinski et
al. 2005)
1200 UTC
1500 UTC
1800 UTC
2100 UTC
Ligurian outflow
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Aerosol distribution over the western
Mediterranean basin
0900 UTC
0600 UTC

• Aerosol loading on March 24, 1998

Local emissions from the region of Toulon
aerosol plume transported from northern Italy
1500 UTC
1200 UTC
Aerosols transported from northern France and
channeled in the Rhône valley (Mistral)
2100 UTC
1800 UTC
Absence of lateral exchanges between the plumes
transported by the Mistral and the Ligurian
outflow (despite gravity wave breaking and wall
separation induced turbulence)
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Zoom on the Gulf of Lion (1100 UTC)comparison
with SeaWifs imagery
C
A
F
E
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)
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Zoom on the Gulf of Lion (1800 UTC)comparison
with LEANDRE 2 Lidar, leg AF
LEANDRE-2 Atmospheric Reflectivity
CHIMERE Atmospheric reflectivity
Long-range transport
Fos-Berre plume
Aerosol-free region
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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)