Transcript Definition of Representativeness

Assessment of Representativeness
of Air Quality Monitoring Stations
Geneva, 11.6.2007
Wolfgang Spangl
26.10. 2006 | Folie 1
Service contract to the Commission for the
Development of the methodologies to
determine representativeness and
classification of air quality monitoring
stations
Contractor to DG ENV:
Umweltbundesamt Austria
Subcontracts with
TNO
Central Institute for Meteorology and Geodynamics, Vienna
26.10. 2006 | Folie 2
Motivation for Assessment of
Representativeness
Information about air quality is required for
the whole territory (e.g. in the AQ framework
Directive 96/62/EC)
 But: Monitoring gives information for distinct
point locations (i.e. monitoring stations)
 Methods to get spatial information about air
quality are required

26.10. 2006 | Folie 3
Spatial Information - Modelling
Spatial information about air quality can be
achieved by modelling. However, models
have some disadvantages:
 Expensive
 High demand on input data (emission,
meteorology, land use, …..)
 Limited resolution (regional, urban, street, …)
 Limited representation of „reality“ due to
various uncertainties
26.10. 2006 | Folie 4
Spatial Information – Representativeness
of monitoring data
Spatial information about air quality can be
achieved by extending measured data to the
“representative area” of a monitoring station.
To delimitate the representative area requires:
1. A definition of „representativeness“
2. Setting quantitative criteria for representativeness
3. The identification of the area which fulfills the criteria
for representativeness, based e.g. on a combination
of model results, emissions, land use data, etc.
26.10. 2006 | Folie 5
“Representative area” of monitoring
stations
Be aware that both
 Definition and
 Quantitative criteria
are deliaberate.
Other definitions and criteria are possible.
Definition and criteria esentially influence the
outcome of representativeness assessment.
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Definition of Representativeness
The area of representativeness is defined by the
criteria:
1. The concentration within a certain range.
The concentration is assessed according to limit and
target values of EC legislation, related to annual
means or annual exceedance numbers.
2. Similar concentrations shall be determined by
similar reasons:
Emissions
Dispersion conditions due to buildings, topography
and climate
Atmospheric transformation and transport 26.10. 2006 | Folie 7
Definition of Representativeness
Statistic parameters related to EC AQ
regulations to determine representativeness:
PM10: Annual mean, 93.2-percentile of daily
mean values (equivalent to 35 days per year
above 50 µg/m³)
NO2: Annual mean
Ozone: 90.4-percentile of daily maximum 8hour mean values (equivalent to 25 days per
year above 120 µg/m³)
26.10. 2006 | Folie 8
Definition of Representativeness
The concentration in the area of
representativeness of a certain AQ MS shall be
within a range of 10% of the total concentration
range observed in Europe.
 PM10: Annual mean: ±5 µg/m³, 93.2-percentile
of daily mean values: ±8 µg/m³
 NO2: Annual mean: ±5 µg/m³, which shall also
be applied to NOx
 Ozone: 90.4-percentile of daily maximum 8hour mean values: ±9 µg/m³
26.10. 2006 | Folie 9
Definition of Representativeness
The spatial variation of parimary pollutants (incl.
NO2) is higher than for partly secondary pollutants
(PM10) and secondary pollutants (Ozone).
Therefore the representative areas, applying these
criteria, are, on general, smaller for NO2 and
larger for Ozone.
26.10. 2006 | Folie 10
Similar reasons for similar
concentrations: Emissions
Classification according to emissions of
 Local road traffic
 Domestic heating
 Industry
3 classes each
 A monitoring site is representative for areas
falling into the same class as the respective
monitoring site
26.10. 2006 | Folie 11
Similar reasons for similar concentrations:
Dispersion and atmospheric transport
Local dispersion due to building structure and
street geometry: street canyon; detached
buildings; flat terrain; exposed
 Regional dispersion due to topography (10km): Flat
terrain; hilly terrain; valley; basin; ……
 Large-scale (100km) Regions with different
topography and climate: Alps (north/south), PoValley, Pre-Alpine Lowlands, Pannonian Plane, ….
 Maximum extension of representative area related
to chemical (trans)formation of NO2, O3, PM10, …
(depending on average wind speed, radius approx
100 km in Central Europe)

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Large-scale Regions with different
topography and climate
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Methods to determine the area of
Representativeness
Sources of spatial information:
 Modelling
 Measurement (regular monitoring networks,
temporal measurements)
 Surrogate information: emission inventories;
surrogate for emission: land use (e.g. CORINE
landcover), TeleAtlas roads), population distribution
Model results and (additional) measurement data are
used to derive relations between surrogate
information and concentrations
26.10. 2006 | Folie 14
Area of Representativeness – based on
model results and land use data
Klagenfurt
(Austria),
NO2
Representative
area of two
monitoring
stations:
 urban
background,
annual mean 27
µg/m³ (yellow)
kerb side,
annual mean 43
µg/m³ (red)
26.10. 2006 | Folie 15
Area of Representativeness – based on
surrogate information
Illmitz (rural background),
Ozone
The area of
representativeness is part
of the Pannonian Plane
(dark green) and excludes:
Area above 300m (brown)
Large cities (blue)
Major roads (red)
26.10. 2006 | Folie 16