International audienceNumerical simulations of pollution events with deterministic models have become easier for the last decade thanks to increasing computer skills. Hence three-dimensional chemistry-transport-runs can be performed on a single workstation for long-term simulation or real-time forecast over large scale areas. Furthermore, fast Internet download and high file storage capacity in data processing make it possible to use a wide database of meteorological parameters and pollutant concentration measurements. The PREV'AIR System rests on those technological progresses for delivering daily air qualiry forecasts in operational conditions

Bessagnet, Bertrand

Dufour, Anne

Honore, Cécile

Malherbe, Laure

Meleux, Frédérik

Peuch, Vincent-Henri

Poisson, Nathalie

Rouil, Laurence

Vautard, Robert

HAL-Ecole des Ponts ParisTech

The PREV’AIR system, an operational system for large scale air quality forecasts over Europe; applications at the local scale

HAL-INSU

PREV’AIR : an operational system for air qualitymonitoring and forecasting over EuropeCe´cile Honore, Laurent Menut, Bertrand Bessagnet, Fre´de´rik Meleux,Laurence Rouil, Robert Vautard, Matthias Beekmann, Nathalie Poisson,Vincent-Henri PeuchTo cite this version:Ce´cile Honore, Laurent Menut, Bertrand Bessagnet, Fre´de´rik Meleux, Laurence Rouil, et al..PREV’AIR : an operational system for air quality monitoring and forecasting over Europe.SKOULOUDIS, A.N., KASSOMENOS, P., BARTZIS, J. 10. International Conference on Har-monisation within Atmospheric Dispersion Modelling for Regulatory Purposes (HARMO 10),Oct 2005, Crete, Greece. pp.123-127, 2005. <ineris-00972527>HAL Id: ineris-00972527https://hal-ineris.ccsd.cnrs.fr/ineris-00972527Submitted on 3 Apr 2014HAL is a multi-disciplinary open accessarchive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come fromteaching and research institutions in France orabroad, or from public or private research centers.L’archive ouverte pluridisciplinaire HAL, estdestine´e au de´poˆt et a` la diffusion de documentsscientifiques de niveau recherche, publie´s ou non,e´manant des e´tablissements d’enseignement et derecherche franc¸ais ou e´trangers, des laboratoirespublics ou prive´s.THE PREVAIR SYSTEM, AN OPERATIONAL SYSTEM FOR LARGE SCALE AIRQUALITY FORECASTS OVER EUROPE; APPLICATIONS AT THE LOCAL SCALECécile Honoré1*, Laurence Rouil1, Frédérik Meleux1 , Laure Malherbe1 , Bertrand Bessagnet1,Robert Vautard2, Nathalie Poisson3, Vincent-Henri Peuch4, Anne Dufour4(1) INER IS , Parc Techno log ique A LATA , BP2 , F-60550 Verneui l -en-Hala t te(2) IPSL , Labora to i re de Mé téo ro log i e Dynamique , École Poly technique , F-91128 Palaiseau cedex( 3 )ADEME , 27 , rue Louis Vicat , F - 75737 Par is cedex 15(4) Mé téo -F rance* corresponding author: cecile.honore@ineris.frINTRODUCTIONNumerical simulations of pollution events with deterministic models hâve become easier for thé lastdécade thanks to increasing computer skills. Hence three-dimensional chemistry-transport-runs canbe performed on a single workstation for long-term simulation or real-time forecast over large scaleareas. Furthermore, fast Internet download and high file storage capacity in data processing make itpossible to use a wide database of meteorological parameters and pollutant concentrationmeasurements.The PREV'AIR System rests on those technological progresses for delivering daily air qualiryforecasts in operational conditions. In fonction since summer 2003, it is thé visible part of a widercollaborative project - thé PREVAIR project - launched by thé French Ministry for Ecology andSustainable Development (MEDD), aiming at: (1) providing technical support on atmosphericpollution management in Europe, in thé framework of negotiations on trans-boundary air pollution;(2) providing large scale national air quality information based on numerical simulations andobservations. The PREVAIR System is a complementary monitoring tool with respect to thé localinformation delivered by thé French qualified associations in charge of régional air qualitymonitoring (AASQA3). It relies on a chain of numerical tools: air quality simulation models,modules ensuring thé provision of meteorological and air quality input data to thèse models,modules enabling thé extraction and use of thé numerical data computed by thé System. The outputsof thé PREVAIR system (secondary pollutants forecasts and maps) are archived to build up a largescale air quality simulation database over Europe.The following public organisations are involved in thé PREVAIR project:• INERIS (National Institute for Industrial Environment and Risks) is a public institution, underthé supervision of thé MEDD, Its mission deals with assessment and prévention of accidentaiand chronic risks due to industrial plants, chemical substances and underground opérations,towards health effects and environment. Within thé PREVAIR project, INERIS is in charge ofdeveloping thé PREVAIR architecture, delivering daily information about air quality; providingand archiving air quality data produced within thé PREVAIR system. The institute alsoparticipâtes to thé development of thé CHIMERE model in collaboration with thé IPSL (seeThis is done through technical programs related to thé CAFE (Clean Air For Europe) project managed by théEuropean Commission, and to thé Convention on Long-Range Trans-boundary Air Pollution of thé United Nations -Economie Commission for Europe.In France, since December 1996, air quality monitoring has been ruled by thé Law on Air and Rational Use of Energy.About 40 qualified associations are in charge of air quality monitoring ail over thé French territory.hereafter). Moreover INERIS carries out air quality studies for thé MEDD including reportingand prospective analysis.• IPSL (Pierre-Simon Laplace Institute) is a research institute in thé field of environment, underthé supervision of thé National Centre for Scientific Research (CNRS). IPSL ensures thédevelopment of thé chemistry-transport model(s) - thé CHIMERE model(s) - used within théPREV'AIR System.• ADEME (Agency for Environment and Energy Management) is a public institution under thésupervision of thé Ministries in charge of research, ecology and energy. It helps implementingpublic policies in thé field of energy and environment at local, national and international levels.ADEME ensures thé gathering, archiving and transmission of real-time air quality data locallycollected by thé AASQA. By this way, ADEME builds up thé BASTER database used by théPREV'AIR System.• Météo-France joined thé System in 2004. The organisation develops another air quality model,MOCAGE, and ensures its operational implementation for thé needs of PREV'AIR.The MEDD financially supports thé PREVAIR project through thé funding of INERIS activity.The PREV'AIR System is briefly presented hereafter, as well as thé first conclusions drawn fronttwo years of opération.ARCHITECTURE OF THE PREV'AIR SYSTEM, INPUT DATA AND OUTPUTSThe PREV'AIR System provides daily air quality forecasts at three spatial scales. Global forecastsare produced by Météo-France with thé chemistry-transport model MOCAGE and transferred everyday to thé PREV'AIR System. Continental and national forecasts are computed by thé chemistry-transport model CHIMERE implemented in thé PREV'AIR forecasting chain. In thé "continental"set up, pollutant concentrations are computed over Western Europe with a 50 km*50 km résolution.In thé "national" set up, pollutant concentrations are computed over France with a 10 km* 10 kmrésolution.Ozone and nitrogen dioxide forecasts hâve been delivered for two years. In october 2003, forecastswere extended to particulate matter. PM10 are assumed to be composed of sulfate, nitrate,ammonium, primary particles, anthropogenic and biogenic secondary species. The aérosol moduleaccounts for 6 bins from 10 nm to 40 \xm. From spring 2005, PM10 account for désert dust, sulfatesand carbonaceous compounds advected from thé domain boundaries. A spécifie émission modulehâve been built to account for soil particles emitted from érosion and resuspension processes. Eachday (D), hourly concentration levels are predicted over a four-day period going from D-1, OOh UTto D+3, OOh UT. The first 24 hours of forecast are actually rather simulations whereas thé next 72ones are strictly speaking forecasts. The meteorological predicted fields necessary to runCHIMERE are obtained in two steps: 1. Low résolution meteorological forecast data aredownloaded from thé ftp server of thé American National Weather Services, where they areproduced by thé Global Aviation Model (AVN) model; 2. High résolution meteorological forecastdata are then locally computed using thé MM5 model.Emission data corne from thé EMEP program4, with hourly, weekly and monthly temporal profilesfrom 1ER5. Contrary to meteorological data that change from day to day, émission data are set onceand for ail.4 Coopérative Program for Monitoring and Evaluation of the Long-range Transmission of Air Pollutants in Europe3 Institut fur Energiewirschaflt und Rationelle Energieanwendung, University of StuttgartObserved air quality data are also used by thé PREV'AIR System (see hereafter). They aretransmitted by various European organisations. For example, thé French real-time air quality dataare downloaded from thé BASTER ftp server and used both to evaluate thé model skills and tocorrect a posteriori thé CHIMERE air quality (D-1) simulations.input data(otherthai!meteo.) ScoresAnalysed maps« Reaf-tlme *observationsOzone, pte en jig m3Prévision dH2e.<>& 1^5 pour >ejour.méOTe•KW - - . | ^ r ^ Aff *s Ï *^'J<|S\'.ûr-cuoIWISS• \m• * ;*o• 634S• 8PMI O r moyenne tournâttëre «n ^ g m3PTV vlsicn du ititiC JOn p'i <r lo ]'.JF nu <i «•' 9 ËBP3É^HB^^s«'.»•M B• 13• S 2• -tf• J5• 3ssWtFigure 2 - Ozone peak and PMio daily mean forecast issued on June 28, 2005 for thé same daySince thé 2003 summer season, thé following output data hâve been made available on a daily basisand can be freely accessed through thé Internet:• Maps of daily maxima and averaged forecast concentrations of ozone and nitrogen dioxide forD-1, D+0, D+l and D+2 at continental and national scale; maps of daily maxima and averagedforecast concentrations of ozone for D-1, D+0, D+l and D+2 at global scale.• Maps of daily maxima and averaged forecast concentrations of particulate matter (PMio andPM2.5) for D-1, D+0, D+l and D+2 at continental scale. Figure 1 displays thé ozone peak andPMio daily average forecasts issued on thé 08th of August 2003 for thé same day (D+0) overWestern Europe.• "Analysed" ozone maps: every morning, ozone peak measurement data coming from théAASQAs are used to readjust thé D-1 ozone peak simulation. A kriging-based procédure isapplied. At each grid node, thé simulated concentration is corrected by a weighted sum of thédifférences between model and measurement. Twice a day (at thé end of thé morning and of théafternoon), thé D+0 ozone peak forecast is corrected in thé same way. Figure 2 displays théabsolute différence (in p,g/m3) between thé ozone peaks simulated by thé CHIMERE model andthé analysed peaks.Qzon», pic en p g iM,tj.-i't.l'.ii'14 P •J 4 '« "4 "4V*V<!* "Q î o r » , p c on .ngi'mS,Correction (almulaUqn-analy^^-"^< ^  A fl *5 j ï" ^ S! A, • \\9 2&V&2OO5qn-analys*»)%i* i - »VS. -/**\j•n1C... Atn^.Tv! B^J>- ' JH !^Figure 3 - Ozone peak analysed map (left) and différences with CHIMERE simulation (right)Reliability and scores of thé PREV AIR SystemForecasting mode:Statistical performance indexes are updated every day and published on thé PREV'AIR web site.The availability of thé AVN data is of primary importance (thé missing data is responsible for 5 %of thé forecast failure). Some performance indexes (see table below) hâve been computed for thélast two summers, using thé ozone peak concentrations measured in France and calculated for D+0by thé PREV'AIR System. Regarding thé ozone peak, thé performances of thé System are quitesatisfying.Statistical IndexesObserved mean ozonepeak (ug/m3) (nuber ofobservations used)Simulated mean ozonepeak (jig/m3)Normalized Bias (%)Normalized MeanSquare Error (%)CorrélationLagD + 0D + 0D + 0D + 0D + 0Summer 2003Rural stations127.3(5244)115.9-8.219.50.81Urban andsuburbanstations121.4(31563)115.4-3.620.60.80Summer 2004Rural stations105.4(4111)104.5-0.818.70.81Suburbanstations101.9(8997)104.42.517.40.83Urbanstations99.6(17039)104.44.818.90.84Analysed maps:A sensitivity study was conducted to assess thé efficiency of the correcting procédure. Two 15-daytest periods were selected in thé summer 2003 season. 103 ozone monitoring stations, mostly ofrural type, were used in thé kriging process. 2 rural, 42 suburban and 151 urban monitoring stationswere kept for validation. At thé end of thé tests, différent error statistics were calculated. As theyindicate, thé choice of thé kriging parameters is satisfactory and thé agreement between model andmeasurement in rural and suburban areas is significantly improved. For example in cross validation,when averaged over thé whole period and thé 103 stations, thé normalised bias and thé root meansquare error decrease by 60% and 26% respectively whereas corrélation increases by 10%. Invalidation at thé suburban stations, thé normalised bias and thé root mean square error decrease by51% and 22% whereas corrélation increases by 8%.USE OF THE PREVAIR AIR QUALITY FORECASTS AT THE LOCAL SCALEIn relation to thé second objective of thé PREV AIR project, numerical air quality forecast datahâve been put at thé disposai of air quality related organisations. The only requirement for thédemanding organisations is to fill in a form specifying thé exact domain on which thé data are to bedelivered. Numerical data are then put every morning on thé users page of thé PREVAIR web site.Two kinds of data are available over thé specified domain: ozone and nitrogen dioxide surface dataand 3D data for 22 chemical species. Up to now, about 40 organisations hâve applied for thisservice, for various applications: Downscaling and mapping of pollutant concentrations; support tolocal expert forecasting; provision of boundary conditions to local scale air quality simulation andforecast models. In that context, several initiatives gathering thé skills and resources of différentAASQA were born in France. In thé SYRSO (Régional System for Ozone Monitoring) andOCARINA (Interrégional Air Quality Mapping Tool) projects, PREV'AIR forecast maps arereprocessed at a local scale and broadcast on thé AASQA websites. In thé ESMERALDA andAIRES régional modelling platforms, which involve AASQA respectively from thé North andcentre part of France and from thé Provence-Alpes-Côtes d'Azur région, PREV'AIR numericaloutputs are used as boundary conditions for high résolution modelling.PERSPECTIVESDifférent ways of improving thé system are being investigated or are planned for thé next months:Ozone forecasting and simulationObservation data can be used not only to correct D-1 simulated maps but also to increase théaccuracy of forecasts. This is particularly relevant in régions of complex terrain, where thémodel résolution is not sufficient to reproduce some local pollution patterns.According to data availability, thé domain considered in thé analysed maps could be extendedby including observations from surrounding European countries.- In thé framework of the GMES PROMOTE and GEMS European projects, PREV'AIR willquickly evolve in thé next few years, including developments both for meteorology andchemistry-transport modeling (CTM). The main goal is to evaluate and improve thé modelbehavior on thé vertical dimension. Thereafter, satellite data assimilation will be carry out.Finally, thé feasibility of using several models to deliver a single forecast (multi modelapproach) will be investigated, by example coupling CHIMERE and MOCAGE models.Aérosol forecastingAérosol forecasts hâve been delivered since winter 2003 (starting end of October). The mostimportant improvement expected for aérosols concerns thé implementation of a more detailedchemical schème for secondary organic formation. More observation data will be used in théanalysis and vérification processes (Italy (ARPA-EMR), Switzerland (NABEL/SAEFL), Poland( ins t i tu te of Environmental Protection, Katowice), Germany (UBA)...).

Hal-Diderot

PREV’AIR : an operational system for air quality
monitoring and forecasting over Europe
Ce´cile Honore, Laurent Menut, Bertrand Bessagnet, Fre´de´rik Meleux,
Laurence Rouil, Robert Vautard, Matthias Beekmann, Nathalie Poisson,
Vincent-Henri Peuch
To cite this version:
Ce´cile Honore, Laurent Menut, Bertrand Bessagnet, Fre´de´rik Meleux, Laurence Rouil, et al..
PREV’AIR : an operational system for air quality monitoring and forecasting over Europe.
SKOULOUDIS, A.N., KASSOMENOS, P., BARTZIS, J. 10. International Conference on Har-
monisation within Atmospheric Dispersion Modelling for Regulatory Purposes (HARMO 10),
Oct 2005, Crete, Greece. pp.123-127, 2005. <ineris-00972527>
HAL Id: ineris-00972527
https://hal-ineris.ccsd.cnrs.fr/ineris-00972527
Submitted on 3 Apr 2014
HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est
destine´e au de´poˆt et a` la diffusion de documents
scientifiques de niveau recherche, publie´s ou non,
e´manant des e´tablissements d’enseignement et de
recherche franc¸ais ou e´trangers, des laboratoires
publics ou prive´s.
THE PREVAIR SYSTEM, AN OPERATIONAL SYSTEM FOR LARGE SCALE AIR
QUALITY FORECASTS OVER EUROPE; APPLICATIONS AT THE LOCAL SCALE
Cécile Honoré1*, Laurence Rouil1, Frédérik Meleux1 , Laure Malherbe1 , Bertrand Bessagnet1,
Robert Vautard2, Nathalie Poisson3, Vincent-Henri Peuch4, Anne Dufour4
(1)
 INER IS , Parc Techno log ique A LATA , BP2 , F-60550 Verneui l -en-Hala t te
(2)
 IPSL , Labora to i re de Mé téo ro log i e Dynamique , École Poly technique , F-91128 Palaiseau cedex
( 3 )ADEME , 27 , rue Louis Vicat , F - 75737 Par is cedex 15
(4) Mé téo -F rance
* corresponding author: cecile.honore@ineris.fr
INTRODUCTION
Numerical simulations of pollution events with deterministic models hâve become easier for thé last
décade thanks to increasing computer skills. Hence three-dimensional chemistry-transport-runs can
be performed on a single workstation for long-term simulation or real-time forecast over large scale
areas. Furthermore, fast Internet download and high file storage capacity in data processing make it
possible to use a wide database of meteorological parameters and pollutant concentration
measurements.
The PREV'AIR System rests on those technological progresses for delivering daily air qualiry
forecasts in operational conditions. In fonction since summer 2003, it is thé visible part of a wider
collaborative project - thé PREVAIR project - launched by thé French Ministry for Ecology and
Sustainable Development (MEDD), aiming at: (1) providing technical support on atmospheric
pollution management in Europe, in thé framework of negotiations on trans-boundary air pollution;
(2) providing large scale national air quality information based on numerical simulations and
observations. The PREVAIR System is a complementary monitoring tool with respect to thé local
information delivered by thé French qualified associations in charge of régional air quality
monitoring (AASQA3). It relies on a chain of numerical tools: air quality simulation models,
modules ensuring thé provision of meteorological and air quality input data to thèse models,
modules enabling thé extraction and use of thé numerical data computed by thé System. The outputs
of thé PREVAIR system (secondary pollutants forecasts and maps) are archived to build up a large
scale air quality simulation database over Europe.
The following public organisations are involved in thé PREVAIR project:
• INERIS (National Institute for Industrial Environment and Risks) is a public institution, under
thé supervision of thé MEDD, Its mission deals with assessment and prévention of accidentai
and chronic risks due to industrial plants, chemical substances and underground opérations,
towards health effects and environment. Within thé PREVAIR project, INERIS is in charge of
developing thé PREVAIR architecture, delivering daily information about air quality; providing
and archiving air quality data produced within thé PREVAIR system. The institute also
participâtes to thé development of thé CHIMERE model in collaboration with thé IPSL (see
This is done through technical programs related to thé CAFE (Clean Air For Europe) project managed by thé
European Commission, and to thé Convention on Long-Range Trans-boundary Air Pollution of thé United Nations -
Economie Commission for Europe.
In France, since December 1996, air quality monitoring has been ruled by thé Law on Air and Rational Use of Energy.
About 40 qualified associations are in charge of air quality monitoring ail over thé French territory.
hereafter). Moreover INERIS carries out air quality studies for thé MEDD including reporting
and prospective analysis.
• IPSL (Pierre-Simon Laplace Institute) is a research institute in thé field of environment, under
thé supervision of thé National Centre for Scientific Research (CNRS). IPSL ensures thé
development of thé chemistry-transport model(s) - thé CHIMERE model(s) - used within thé
PREV'AIR System.
• ADEME (Agency for Environment and Energy Management) is a public institution under thé
supervision of thé Ministries in charge of research, ecology and energy. It helps implementing
public policies in thé field of energy and environment at local, national and international levels.
ADEME ensures thé gathering, archiving and transmission of real-time air quality data locally
collected by thé AASQA. By this way, ADEME builds up thé BASTER database used by thé
PREV'AIR System.
• Météo-France joined thé System in 2004. The organisation develops another air quality model,
MOCAGE, and ensures its operational implementation for thé needs of PREV'AIR.
The MEDD financially supports thé PREVAIR project through thé funding of INERIS activity.
The PREV'AIR System is briefly presented hereafter, as well as thé first conclusions drawn front
two years of opération.
ARCHITECTURE OF THE PREV'AIR SYSTEM, INPUT DATA AND OUTPUTS
The PREV'AIR System provides daily air quality forecasts at three spatial scales. Global forecasts
are produced by Météo-France with thé chemistry-transport model MOCAGE and transferred every
day to thé PREV'AIR System. Continental and national forecasts are computed by thé chemistry-
transport model CHIMERE implemented in thé PREV'AIR forecasting chain. In thé "continental"
set up, pollutant concentrations are computed over Western Europe with a 50 km*50 km résolution.
In thé "national" set up, pollutant concentrations are computed over France with a 10 km* 10 km
résolution.
Ozone and nitrogen dioxide forecasts hâve been delivered for two years. In october 2003, forecasts
were extended to particulate matter. PM10 are assumed to be composed of sulfate, nitrate,
ammonium, primary particles, anthropogenic and biogenic secondary species. The aérosol module
accounts for 6 bins from 10 nm to 40 \xm. From spring 2005, PM10 account for désert dust, sulfates
and carbonaceous compounds advected from thé domain boundaries. A spécifie émission module
hâve been built to account for soil particles emitted from érosion and resuspension processes. Each
day (D), hourly concentration levels are predicted over a four-day period going from D-1, OOh UT
to D+3, OOh UT. The first 24 hours of forecast are actually rather simulations whereas thé next 72
ones are strictly speaking forecasts. The meteorological predicted fields necessary to run
CHIMERE are obtained in two steps: 1. Low résolution meteorological forecast data are
downloaded from thé ftp server of thé American National Weather Services, where they are
produced by thé Global Aviation Model (AVN) model; 2. High résolution meteorological forecast
data are then locally computed using thé MM5 model.
Emission data corne from thé EMEP program4, with hourly, weekly and monthly temporal profiles
from 1ER5. Contrary to meteorological data that change from day to day, émission data are set once
and for ail.
4
 Coopérative Program for Monitoring and Evaluation of the Long-range Transmission of Air Pollutants in Europe
3
 Institut fur Energiewirschaflt und Rationelle Energieanwendung, University of Stuttgart
Observed air quality data are also used by thé PREV'AIR System (see hereafter). They are
transmitted by various European organisations. For example, thé French real-time air quality data
are downloaded from thé BASTER ftp server and used both to evaluate thé model skills and to
correct a posteriori thé CHIMERE air quality (D-1) simulations.
input data
(other
thai!
meteo.) Scores
Analysed maps
« Reaf-tlme *
observations
Ozone, pte en jig m3
Prévision dH2e.<>& 1^5 pour >ejour.méOTe
•KW - - . | ^ r ^ Aff *s Ï *^
'J<|
S
\'.û
r-c
uo
IW
ISS
• \m
• * ;
*o
• 63
4S
• 8
PMI O
 r moyenne tournâttëre «n ^ g m3
PTV vlsicn du ititiC JOn p'i <r lo ]'.JF nu <i «•
' 9 ËBP3É^HB^^
s«
'.»
•M B
• 13
• S 2
• -tf
• J5
• 3
ss
W
t
Figure 2 - Ozone peak and PMio daily mean forecast issued on June 28, 2005 for thé same day
Since thé 2003 summer season, thé following output data hâve been made available on a daily basis
and can be freely accessed through thé Internet:
• Maps of daily maxima and averaged forecast concentrations of ozone and nitrogen dioxide for
D-1, D+0, D+l and D+2 at continental and national scale; maps of daily maxima and averaged
forecast concentrations of ozone for D-1, D+0, D+l and D+2 at global scale.
• Maps of daily maxima and averaged forecast concentrations of particulate matter (PMio and
PM2.5) for D-1, D+0, D+l and D+2 at continental scale. Figure 1 displays thé ozone peak and
PMio daily average forecasts issued on thé 08th of August 2003 for thé same day (D+0) over
Western Europe.
• "Analysed" ozone maps: every morning, ozone peak measurement data coming from thé
AASQAs are used to readjust thé D-1 ozone peak simulation. A kriging-based procédure is
applied. At each grid node, thé simulated concentration is corrected by a weighted sum of thé
différences between model and measurement. Twice a day (at thé end of thé morning and of thé
afternoon), thé D+0 ozone peak forecast is corrected in thé same way. Figure 2 displays thé
absolute différence (in p,g/m3) between thé ozone peaks simulated by thé CHIMERE model and
thé analysed peaks.
Qzon», pic en p g iM,
tj.-i't.l'.ii
'1
4 P •
J 4 '
« "
4 "
4V
*V
<!* "
Q î o r » , p c on .ngi'mS,
Correction (almulaUqn-analy
^^-"^< ^  A fl *5 j ï" ^ S
!
 A
, • \
\9 2&V&2OO5
qn-analys*»)
%
i
* i - »
VS. -
/*
*\
j
•n
1C
... Atn^.Tv! B^J>- ' JH !^
Figure 3 - Ozone peak analysed map (left) and différences with CHIMERE simulation (right)
Reliability and scores of thé PREV AIR System
Forecasting mode:
Statistical performance indexes are updated every day and published on thé PREV'AIR web site.
The availability of thé AVN data is of primary importance (thé missing data is responsible for 5 %
of thé forecast failure). Some performance indexes (see table below) hâve been computed for thé
last two summers, using thé ozone peak concentrations measured in France and calculated for D+0
by thé PREV'AIR System. Regarding thé ozone peak, thé performances of thé System are quite
satisfying.
Statistical Indexes
Observed mean ozone
peak (ug/m3) (nuber of
observations used)
Simulated mean ozone
peak (jig/m3)
Normalized Bias (%)
Normalized Mean
Square Error (%)
Corrélation
Lag
D + 0
D + 0
D + 0
D + 0
D + 0
Summer 2003
Rural stations
127.3
(5244)
115.9
-8.2
19.5
0.81
Urban and
suburban
stations
121.4
(31563)
115.4
-3.6
20.6
0.80
Summer 2004
Rural stations
105.4
(4111)
104.5
-0.8
18.7
0.81
Suburban
stations
101.9
(8997)
104.4
2.5
17.4
0.83
Urban
stations
99.6
(17039)
104.4
4.8
18.9
0.84
Analysed maps:
A sensitivity study was conducted to assess thé efficiency of the correcting procédure. Two 15-day
test periods were selected in thé summer 2003 season. 103 ozone monitoring stations, mostly of
rural type, were used in thé kriging process. 2 rural, 42 suburban and 151 urban monitoring stations
were kept for validation. At thé end of thé tests, différent error statistics were calculated. As they
indicate, thé choice of thé kriging parameters is satisfactory and thé agreement between model and
measurement in rural and suburban areas is significantly improved. For example in cross validation,
when averaged over thé whole period and thé 103 stations, thé normalised bias and thé root mean
square error decrease by 60% and 26% respectively whereas corrélation increases by 10%. In
validation at thé suburban stations, thé normalised bias and thé root mean square error decrease by
51% and 22% whereas corrélation increases by 8%.
USE OF THE PREVAIR AIR QUALITY FORECASTS AT THE LOCAL SCALE
In relation to thé second objective of thé PREV AIR project, numerical air quality forecast data
hâve been put at thé disposai of air quality related organisations. The only requirement for thé
demanding organisations is to fill in a form specifying thé exact domain on which thé data are to be
delivered. Numerical data are then put every morning on thé users page of thé PREVAIR web site.
Two kinds of data are available over thé specified domain: ozone and nitrogen dioxide surface data
and 3D data for 22 chemical species. Up to now, about 40 organisations hâve applied for this
service, for various applications: Downscaling and mapping of pollutant concentrations; support to
local expert forecasting; provision of boundary conditions to local scale air quality simulation and
forecast models. In that context, several initiatives gathering thé skills and resources of différent
AASQA were born in France. In thé SYRSO (Régional System for Ozone Monitoring) and
OCARINA (Interrégional Air Quality Mapping Tool) projects, PREV'AIR forecast maps are
reprocessed at a local scale and broadcast on thé AASQA websites. In thé ESMERALDA and
AIRES régional modelling platforms, which involve AASQA respectively from thé North and
centre part of France and from thé Provence-Alpes-Côtes d'Azur région, PREV'AIR numerical
outputs are used as boundary conditions for high résolution modelling.
PERSPECTIVES
Différent ways of improving thé system are being investigated or are planned for thé next months:
Ozone forecasting and simulation
Observation data can be used not only to correct D-1 simulated maps but also to increase thé
accuracy of forecasts. This is particularly relevant in régions of complex terrain, where thé
model résolution is not sufficient to reproduce some local pollution patterns.
According to data availability, thé domain considered in thé analysed maps could be extended
by including observations from surrounding European countries.
- In thé framework of the GMES PROMOTE and GEMS European projects, PREV'AIR will
quickly evolve in thé next few years, including developments both for meteorology and
chemistry-transport modeling (CTM). The main goal is to evaluate and improve thé model
behavior on thé vertical dimension. Thereafter, satellite data assimilation will be carry out.
Finally, thé feasibility of using several models to deliver a single forecast (multi model
approach) will be investigated, by example coupling CHIMERE and MOCAGE models.
Aérosol forecasting
Aérosol forecasts hâve been delivered since winter 2003 (starting end of October). The most
important improvement expected for aérosols concerns thé implementation of a more detailed
chemical schème for secondary organic formation. More observation data will be used in thé
analysis and vérification processes (Italy (ARPA-EMR), Switzerland (NABEL/SAEFL), Poland
( ins t i tu te of Environmental Protection, Katowice), Germany (UBA)...).


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The PREV’AIR system, an operational system for large scale air quality forecasts over Europe; applications at the local scale

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