HTAP Multi-model Assessment of Ozone Source-receptor Relationships. Arlene M. Fiore

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1 HTAP Multi-model Assessment of Ozone Source-receptor Relationships Arlene M. Fiore Kees Cuvelier, Frank Dentener (JRC) and the TF HTAP Modeling Team including Rokjin Park (GEOS-Chem v ) and Marta Garcia Vivanco (GEOS-Chem 45) Draft interim report at 3 rd GEOS-Chem Users Meeting, Harvard University April 13, 27

2 TF HTAP mission: Develop a fuller understanding of hemispheric transport of air pollution to inform future negotiations under CLRTAP Convention on Long-Range Transboundary Air Pollution (CLRTAP) 49 parties in Europe, North America, and Central Asia Co-chairs: Terry Keating (U.S. EPA) and André Zuber (EC) TF HTAP Products: 27 (Interim) and 29 (Final) Assessment reports

3 Literature Estimates of Surface O 3 Enhancements at Northern Mid-latitudes from Hemispheric Transport USA EU ASIA Thin dashes: seasonal mean RECEPTOR REGIONS Thick dashes: events Solid bars: annual means SOURCE REGIONS: N. AMERICA EUROPE ASIA BACKGROUND Estimates are from studies cited in current draft of TF HTAP interim report Ch5, updated from tables in Holloway et al., ES&T, 23 and Fiore et al., EM, 23 Difficult to conduct meaningful assessment due to differences in: 1) methods 2) regional definitions 3) reported metrics

4 HTAP Multi-model approach to estimate intercontinental source-receptor (S-R) relationships for ozone NA Conduct base simulations with 3-D models horizontal resolution of 4 5 or finer 21 meteorology each group s best estimate for emissions in 21 methane set to a uniform value of 176 ppb Conduct sensitivity simulations (17 total) 2% decreases in: anthrop. emis. in HTAP regions for NO, CO, NMVOC individually anthrop. emis. of all O 3 and aerosol precursors in HTAP regions global CH 4 EU SA EA

5 Surface O 3 seasonal cycles in base simulations over the HTAP regions 17-model mean 17-model range GEOS-Chem 22.5 GEOS-Chem 45 Surface O 3 (ppbv) EU SA Month of 21 Model range often spans ~15 ppbv NA EA Other HTAP O 3 models: CAMCHEM ECHAM5-HAMMOZ EMEP FRSGCUCI GEMAQ INCA LLNL-IMPACT-T5a MOZARTGFDL MOZECH OsloCTM2 STOC-HadAM3 STOCHEM TM5-JRC ULAQ UM-CAM

6 Recent ACCENT multi-model surface O 3 vs. observations in HTAP regions: NA and EU SW US SE US US Great Lakes OBS Multi-model mean standard deviation range North America SW US: 11 sites SE US: 12 sites US Great Lakes: 13 C. Mediterranean C. Europe Europe and North Africa Middle East C. Mediterranean: 21 C. Europe: 11 sites Middle East: 1 site 25 participating models Year 2 Ellingsen et al., in prep

7 Estimates of S-R relationships: Annual mean surface ozone decrease due to 2% global methane reduction 2. ppbv Full range of 14 models.5. EUROPE N. AMER. S. ASIA E. ASIA HTAP receptor region GEOS-Chem 22.5 GEOS-Chem 45 1 ppbv O 3 decrease over all NH receptor regions Consistent with prior studies What causes the ~1 ppbv range across individual models? -- eamine ozone production efficiency; NO :VOC ratios

8 Decrease in surface O 3 (ppbv) Estimates of S-R relationships: Sensitivity of surface O 3 to NO sources during season of ma domestic O 3 production Source region: EU NA SA EA Sum of 3 foreign regions Largest S-R pair: NA EU Smallest HTAP influence on NA Largest HTAP influence on SA Receptor region: EU NA SA EA Season:JJA JJA SON JJA Σ(2% decreases in foreign NO ) 2% decrease in domestic NO = 1-3% 14 model range GEOS-Chem Eamine springtime when intercontinental transport typically peaks Compare role of NO emissions with other O 3 precursors Similar impact from all 3 foreign source regions

9 Estimates of S-R relationships: Springtime surface O 3 decrease in HTAP receptor regions from 2% reductions of O 3 precursors SOURCE REGIONS: EU NA SA EA Σ 3 foreign regions ppbv RECEPTOR = NORTH AMERICA NO VOC CO ALL EA/EU contribute similarly EU VOC at least as important as NO Σ( 2% foreign emis.) -2% domestic emis. 55% ppbv Larger uncertainty in role of foreign VOC RECEPTOR = EAST ASIA NO VOC CO ALL EU and NA SA Σ( 2% foreign emis.) -2% domestic emis. 85%

10 Some remaining questions... (to be eamined as part of the TF HTAP project) Overall conclusion from previous analysis: Range of estimates narrows from that in the literature under HTAP setup Which processes contribute most to uncertainty in S-R relationships? Insights from idealized tracer eperiments Normalize model response to emission perturbations How can we best test models of hemispheric transport of air pollution? Need to test processes (eport, chemical evolution, miing to surface) Can 2% emission decreases be scaled to reductions of other magnitudes? Yes for CH 4 ; simulations underway for other O 3 precursors Role of hemispheric transport in polluted vs. background conditions? Eamine range of model responses across the O 3 distribution How will climate change affect hemispheric transport of air pollution? for more info and to comment on draft 27 interim report