Diapositiva 1

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Ozone modeling over Italy a sensitivity analysis
to precursors using BOLCHEM air quality model
Mihaela Mircea1, Massimo D'Isidoro1, Alberto
Maurizi1, Maria Gabriella Villani1, Andrea
Buzzi1, Sandro Fuzzi1, Francesco
Tampieri1 Gabriele Zanini2, Fabio Monforti2, Lina
Vitale2 1Istituto di Scienze dellAtmosfera e
del Clima, CNR, Bologna, Italy 2ENEA,Italian
Agency for New Technologies, Energy and the
Environment, Via Martiri di Monte Sole 4, 40129
Bologna, Italy
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Objectives

• to investigate the sensitivity of ozone
  concentration to the reduction of NOx and VOC for
  few periods during the years 1999 and 2003 over
  the whole Italy
• to asses the relative importance of precursors in
  reducing the ozone levels identifying the regions
  of Italy where local emissions strategies could
  not be effective

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Motivation

• there is no such study only studies over
  Northern Italy
• in some areas, the ozone concentrations can be
  controlled by transboundary processes and that it
  cannot be ruled out by simulating a small area.
• the topography of Italy is very complex and leads
  to very complicate circulations features.
• Italy is in a geographic position (from ca. 37o
  to 47o lat North) that lead to various climate
  features.
• The ozone episodes to simulate were chosen for
  the year 1999 because it is used as a reference
  year in meteorological studies and for the summer
  2003 because it was characterized by very high
  temperatures for a many days.

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BOLCHEM flow chart
Meteorological Model (BOLAM)
Chemistrytransport model (CTM)
Transport/dispersion
Winds, T, q
Gas Chemistry (SAPRC90/CB4)
Emissions
Dry Deposition
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Photochemical mechanisms

• CB-IV (Gery et al., 1989) lumped-structure
  condensed mechanism
• -85 reactions and 30 chemical species
• -organics are grouped according to bond type (for
  example, as carbon single bonds, carbon double
  bounds or carbonyl bounds)
• -organic species are treated explicitly (e.g.
  formaldehyde, ethene, isoprene), represented by
  carbon bond (PAR single bonded one carbon atom,
  OLE two carbon atoms) or molecular (TOL and XYL
  aromatic hydrocarbons) surrogates according with
  their chemistry or importance in the environment.
• SAPRC90 (Carter, 1990) lumped-molecular
  condensed mechanism
• -131 reactions with 35 chemical species
• -calculate the kinetic and mechanistic parameters
  for lumped species in the mechanism created for
  representative emissions profile (mole-weighted
  approach)
• -organics species are treated explicitly (e.g.
  formaldehyde, acetaldehyde, etc) or represented
  by molecules as alkane, alkenes, aromatics, etc.

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Chemistry is coupled online with meteorology

• Meteorology and chemistry use
• same transport scheme (WAF (Weighted Average
  Flux) 3-d advection scheme)
• same grid horizontal and vertical components
  (the vertical coordinate system is
  terrain-following (s), with variables distributed
  on a non-uniformly spaced staggered Lorenz grid.
  the horizontal discretization uses geographical
  coordinates on an Arakawa C-grid)
• same physics for the subgrid-scale transport (for
  example vertical diffusion in surface layer and
  PBL parameterization depend on the Richardson
  number)
• same time step

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Emissions, initial and boundary conditions

• The chemical fields are driven by hourly surface
  emissions and 3 hourly lateral boundary
  conditions after the initialisation.
• Emissions, initial and boundary conditions are
  produced by Thoscane model (Zanini et al.,
  2004).
• The emission inventory includes the ship
  emissions and the point source emissions are also
  considered in the simulations.

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Model configuration and meteorological inputs

• The model domain extends between NW (20.77,
  47.55) NE (4.82 - 47.55) SW (6.17 - 35.79) SE
  (19.42 35.79).
• The horizontal resolution used in the
  simulations is of 20 km. The vertical resolution
  includes 33 sigma vertical layers from surface to
  the tropopause. The lower layer is approximately
  20m thick above the surface.
• The meteorological fields are supplied by ECMWF.
  The lateral boundary conditions are updated every
  6 hours. The weather fields were re-initialized
  every 48 hours with the analyses in order to
  avoid an excessive error growth in the
  meteorological forecast.

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Evaluation of model performance

• 1999 4 clear sky periods selected based on
  Meteosat Images of Europe
• January 20-25
• June 1-4
• July 1-5
• August 5-8

The model runs are on an grid between fine and
coarse, therefore the model results are only
compared with observations at rural and
semi-rural locations.
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Time series of observed and predicted O3 mixing
ratio of gases at sites (1)
Atmospheric Chemistry
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Time series of observed and predicted O3 mixing
ratio of gases at sites (2)
Atmospheric Chemistry
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Quantitative performance statistics for hourly
concentrations of O3
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NOx reduced(-35)
Base case
VOC reduced(-35)
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Differences in ozone concentrations
DO3O3(65VOC)-O3(65NOx)
Chemical regimes over Italy
DO3 gt 0 NOx limited area DO3 lt0 VOC limited area
SAPRC90
CB4
ppb
ppb
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Areas selected for the analysis
Center of the area Lat Lon Size (km X km)
Milano 45o28 9o10 160x160
Genova 44o25 8o54 80x80
Venezia 45o26 12o19 240x240
Roma 41o54 12o28 80x80
Napoli 40o51 14o16 80x80
Taranto 40o25 17o14 80x80
Pachino 36o15 15o05 100x100
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NOx reduced(-35)
VOC reduced(-35)
DO3(ppb)
CB4
DO3local-global reductions
SAPRC90
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(No Transcript)
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Extreme summer 2003
DO3O3(65VOC)-O3(65NOx)
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Fraction of VOC or NOx limited area
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O3 increase due to the increase in isoprene
emissions
ppb
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Preliminary conclusions

• The differences in the predicted ozone
  concentrations due to the photochemical
  mechanisms are comparable to those obtained by
  reducing the emissions of NOx or VOC
• The distribution and the intensity (differences
  in ozone concentration) of VOC or NOx limited
  areas depend on the photochemical mechanism. For
  example, in the same meteorological and
  environmental conditions, a region can be VOC or
  NOx sensitive according with the photochemical
  mechanism used.
• The local reduction of VOC was efficient for
  Milano and Venice areas. In the other regions,
  significant increase in ozone concentration was
  observed by reducing locally both the NOx or VOC
  emissions.
• The increase of isoprene leads to substantial
  increase in the concentration of ozone at some
  locations (up to 25), therefore, the
  uncertainties in isoprene emissions can bias the
  air quality design.

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ACKNOWLEDGEMENTS

• GEMS and ACCENT EU-projects
• ICTP Programme for Training and Research in
  Italian Laboratories, Trieste, Italy

Atmospheric Chemistry ISAC (CNR)