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CityDelta background

CityDelta background. EC4MACS «  urban modelling  » component : better account for the urban dimension in the integrated assessment modelling What ? : concentration increment (or decrement ) due to the city itself

bertha-hardy
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CityDelta background

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  1. CityDelta background • EC4MACS « urbanmodelling » component : betteraccount for the urban dimension in the integratedassessmentmodelling • What? : concentration increment (or decrement) due to the city itself • Why? : to correct coarseresolution model used in integratedassessment • How? : • Can bedefined as δ=Chigh- Clow • In the former CityDelta exercice : with a set of CTM results over 7 cities in Europe thatlead to a single formula for all Europeancities • CHIMERE highresolution (7 km) simulation over a large part of Europe [ECMWF data + WRF ; EMEP emissions]

  2. Improvingemissions • « residentialemissions » (SNAP2) reallocatedwith population density (+ woodburningshareurban vs rural with french data) • « Crops » landuse proxy for Agricultural sector • « built-up » landuse proxy for the otheranthropogenicsectors • « roadmap » proxy for road trafficemissions (in progress) PPM2.5 emissionbefore PPM2.5 emissionafter

  3. Inluence of vertical resolution • Three simulations performedwith CHIMERE over the Paris area • C8 : Referencerunwith 8 levels (first at 40 m) up to 500 Hpa • C20 : Simulation with 20 levels (first at 40 m) up to 500 Hpa • C9 : Simulation with 9 levels (first at 10 m) up to 500 Hpa

  4. Inluence of vertical resolution Coll. L. Menut LMD/IPSL-CNRS

  5. Improving horizontal resolution – why 7 km resolution? • For secondarypollutantslike O3, 12 km seems an optimal resolution (Valari and Menut , 2008) • From the POMI exercize , no gain from 6km to 3 km (even for PM) • Computing time…(increase of gridcellnumber and decrease of time step)

  6. COARSE (50 km) The simulation domains NEST (7km) 300 x 400 grid points! • A highresolutionrunisperformed over the greydomain (7 km) (i,j) • A highresolutionrunisperformed over the greydomain • For eachsmallcell (i,j) : • the highres. conc : • the coarseres. Conc. : • the averaged concentration : • DELTA assumed to be:

  7. Simulation results • Two simulations performed for the year 2006 : • A simulation withonlyprimaryparticulatematter and lowlevel sources (SNAP 2, 7 and partly 3)  PPM run • A full chemistryrun Delta PPM2.5 species µg.m-3 2006 Month

  8. [PPM based delta] versus [full PM based delta] µg.m-3 PPM run: Delta PPM2.5 species µg.m-3 FULLCHEM run: Delta PM2.5 species

  9. Model underestimations • Usuallywe have an underestimate of PM • SOA formation (background issue) • Wildfires (60% of the total PM10 emissions in Europe! including a part of Russia - AQMEII project) (background issue) • Domesticwoodburning in wintertime • Road trafficresuspension • Resuspensionfromsoilerosion (background issue) • Emission vertical profiles • Meteorology (kzcalculation, wetdeposition)

  10. PM2.5 Jan 2006 – using EMEP vertical profile for SNAP 2 emissions

  11. PM2.5 Jan 2006 – putting all SNAP 2 in the first CHIMERE layer

  12. Impact of emision injection heights of city deltas

  13. Conclusion • Downscalingmethod of EMEP emissiondatasetimproved for ourhighresolution • High resolutionrunwasperformed over Europe to computecitydeltas • Improvment of CHIMERE runsat all resolutions (high and low) • Define a strategy to use « deltas » in integratedassessment model

  14. Extra slides

  15. About validation… • Pratically, itis not possible to validate a « delta » δ=Chigh- Clow; Chigh and Clow are comparable with measurements, but δ ?? • What is the order of magnitude of PM2.5 deltas? With measurements in 2009, we roughly estimate the delta =1.6 µg.m-3versus0.94 µg.m-3found in our work (for 2006). • Validation on PM2.5 for the “full chemistry run” City

  16. Box model approximation • Reminder : a coefficient K isdefined by city as δ=K.Q • Possible implementation of a box model by city to introduce a sensitivity to meteorologicalparameter • Box model increment : • Xcity= diameter of the city (m) • Xbckg= charateristic length of the background (m) (EMEP grid compliant) • Scity= surface of the city (m²) • Sbckg= surface of the low resolution cell (m2) • Q= city emissions (kg/s) • h= ABL height • U= Wind speed at 10m (m/s)

  17. CityDelta background – are observations useful to compute the citydelta? • Main goal is to correct a coarse EMEP simulation • Wecanconsider : δideal=Creal – Clowthen, δideal corrects the model behavior and the lack of sources (using optimal interpolation methods) • Then , δideal= δknownphysics andemissions + δmissingsources & processes • And , δideal=K.Q + δmissingsources & processes • We must correct onlywhatwe know, implementing observations in the methodologyintroduces a biasdifficult to handle in GAINS calculations What to do withthisterm? Nothing! Computed in thiswork

  18. Background O3 (AVERAGE) ppb Background O3 (lowresol)

  19. AQMEII project Domain-wide yearly emissions [tons/y]

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