CITYDELTA

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CITY-DELTA
Delta results and interpretation
C. Cuvelier and P. Thunis JRC-IES, Ispra
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4 DELTAs

• Model Delta
• Emission Delta
• Scale Delta
• City Delta

• How is the model variability depending of the
  city?
• Is the model variability larger at LS or at FS
  ???
• Is the model variability similar for all emission
  scenarios ?
• Do LS and FS models show similar differences in
  all cities ?
• Do LS and FS models show similar differences for
  all scenarios ?
• Is the response to a given emission reduction
  similar in all cities ?

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Evaluation of the deltas

• On which pollutant ? PM, O3
• On which spatial area ? City Centre vs City
  area
• On which time period ? Summer vs winter (for
  PM)
• On which indicator ? MeanT, SOMO, Exc. Days

• Selected indicators
• Mean T
• Exceedance days

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The ENSEMBLE model
OZONE
PM10
Day1 Day2 Day3 Day4 Exceedances Model 1 70
70 40 40 2 Model 2 40 40 70 70
2 ENSEMBLE 55 55 55 55 0
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How is the model variability depending on the
city?
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City variability
O3 MeanT (CD)
PM10 Winter (CD)
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O3 Indicator variability
MeanT (CD)
SOMO (CD)
Exc. Days (CD)
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How is the model variability depending on the
city?

• FS and LS models are in close agreement in the
  different cities for predicting mean O3 and PM
  levels.
• Among the different cities, the model variability
  is the largest in Milan.
• This variability is in general larger for PM than
  for O3
• The FS model variability is often larger than the
  difference between LS and FS ensemble models.

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Is the model variability similar for all
emission scenarios ?
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MeanT summer O3 ppb in City-Domain
Berlin
Berlin
FS
FS
LS
LS
Katowice
Katowice
London
London
Milan
Milan
Paris
Paris
Prague
Prague
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Is the model variability similar for all
emission scenarios ?

• The variability in the responses of FS and LS
  models to emission reductions is within a range
  of 2 ppb.
• The variability is the largest for the BCA?CLE
  and NOx reductions.
• The VOC emission reduction is where models do
  agree most.
• In Milan, the variability is the largest, and
  show non-linearities in the CLE?NOx/2?NOx
  reductions.

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Do LS and FS models show similar differences in
all cities ?
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O3 MeanT CC
O3 Exc. Days CC
PM10 MeanT Winter CC
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Do LS and FS models show similar differences in
all cities ?

• For the base case emissions, LS models always
  predict larger o3 indicators than FS models for
  all cities except London.
• Differences between LS and FS models are the
  largest in Milan and the smallest in London and
  Paris.
• For PM, LS models predict smaller PM
  concentrations than FS models.

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Do LS and FS models show similar differences for
all scenarios ?
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NOx Reduction
O3 SOMO (CD)
VOC Reduction
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NOx Group Reduction
PM10 Winter (CD)
VOC Group Reduction
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Do LS and FS models show similar differences for
all scenarios ?

• BCA?CLE and NOx reductions are more effective for
  LS than for FS.
• VOC reductions are less or equally effective for
  LS than for FS.
• PM All reductions are less effective for LS than
  for FS. Differences are not significant for the
  VOC group reductions.

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Is the response to a given emission reduction
similar in all cities ?
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• NO because the impact of an emission reduction
  depends on the initial NOx/VOC ratio of each city
  emission inventory
• Comparison of the emission delta among cities is
  difficult since the reduction percentages are
  city-dependant.

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General conclusions

• The impact of further to CLE emission reductions
  is much lower than the impact of emission
  reductions from 1999 to CLE.
• In general, LS and FS models do agree in their
  responses to emission reduction scenarios but
• Differences increase with threshold type of
  indicators
• Differences increase when focusing on smaller
  areas (CC)
• Milan is the city where models show the largest
  variability in their responses. This could be due
  to the difficulty of representing the meteorology
  or the chemical regime in this geographically
  complex area.
• The FS models variability is often larger than
  the difference between the LS and FS model
  ensembles.
• The PM model variability is larger in winter than
  in summer.
• For PM and VOC emission reductions, LS models
  predict less effective changes (in PM and O3)
  than FS models. The reverse is true for the
  impact of NOx emission reductions on O3 levels.