ECONOMIC COMMISSION FOR EUROPE Geneva HEMISPHERIC TRANSPORT OF AIR POLLUTION 2007 AIR POLLUTION STUDIES No. 16 Interim report prepared by the Task Force on Hemispheric Transport of Air Pollution acting within the framework of the Convention on Long-range Transboundary Air Pollution UNITED NATIONS New York and Geneva, 2007 Symbols of United Nations documents are composed of capital letters combined with figures. Mention of such symbols indicates a reference to a United Nations document. The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. In United Nations texts, the term “ton” refers to metric tons (1,000 kg or 2,204.6 lbs). Acknowledgements The Task Force Co-Chairs and the secretariat would like to acknowledge the assistance of EC/R, Inc., in preparing this publication. We would also like to acknowledge the invaluable contribution of the individual experts and the Convention’s programme centres and task forces. ECE/EB.AIR/94 UNITED NATIONS PUBLICATION Sales No. E.08.II.E.5 ISSN 1014-4625 ISBN 978-92-1-116984-3 Copyright © United Nations, 2007 All rights reserved UNECE Information Service Phone: +41 (0) 22 917 44 44 Palais des Nations Fax: +41 (0) 22 917 05 05 CH-1211 Geneva 10 E-mail: [email protected] Switzerland Website: http://www.unece.org List of contributors Report Co-Chairs Terry Keating United States André Zuber European Community Executive summary Coordinating lead authors Terry Keating United States André Zuber European Community Contributing authors Glynis Lough United States Chapter 1: Introduction Terry Keating United States André Zuber European Community Chapter 2: Conceptual overview Coordinating lead authors Owen Cooper United States Andreas Stohl Norway Contributing authors Ruth Doherty United Kingdom Peter Hess United States Chapter 3: Observational evidence and capabilities Chapter Coordinating lead authors David Parrish United States Section coordinating lead authors David Edwards United States Joseph Prospero United States Daniel Jaffe United States Lorraine Remer United States Randall Martin Canada Contributing authors Mathew Evans United Kingdom Stuart Penkett United Kingdom Shiro Hatakeyama Japan Rich Scheffe United States Gerard Jennings Ireland Kjetil Torseth Norway Other contributors Hajime Akimoto Japan Russell Dickerson United States John Burrows Germany Ulrich Platt Germany Tony Hollingsworth United Kingdom iii Chapter 4: Emissions and projections Coordinating lead authors Zbigniew Klimont Austria David Streets United States Contributing authors Alex Guenther United States John van Aardenne European Community Kristin Rypdal Norway Other contributors He Kebin China Syed Shoaib Raza Pakistan Toshimasa Ohara Japan Chapter 5: Global and regional modelling Chapter coordinating lead authors Gregory Carmichael United States Frank Dentener European Community Section Coordinating lead authors Richard Derwent United Kingdom Michael Schulz France Arlene Fiore United States Oliver Wild United Kingdom Michael Prather United States Contributing authors Peter Hess United States David Stevenson United Kingdom Tracey Holloway United States Christiane Textor France Dorothy Koch United States Oliver Wild United Kingdom Martin Schultz Germany Other contributors Isabelle Bey Switzerland Rokjin Park United States Carey Jang United States Hiroshi Tanimoto Japan Qinbin Li United States Donald Wuebbles United States Contributors to HTAP Intercomparison Cynthia Atherton United States Veronica Montanaro Italy Daniel Bergmann United States Rokjin Park United States Isabelle Bey Switzerland Kristy Pringle United Kingdom Huisheng Bian United States John Pyle United Kingdom Mian Chin United States Michael Sanderson United Kingdom Kees Cuvelier European Community Martin Schultz Germany Frank Dentener European Community Michael Schulz France Thomas Diehl United States Drew Shindell United States Ruth Doherty United Kingdom David Stevenson United Kingdom Greg Faluvegi United States Susan Strahan United States Arlene Fiore United States Sophie Szopa France Gerd Folberth Switzerland Toshiko Takamura Japan Michael Gauss Norway Christiane Textor France Sunling Gong Canada Philippe Thunis European Community Peter Hess United States Marta GarcíaVivanco Spain Larry Horowitz United States Oliver Wild United Kingdom Ivar S.A. Isaksen Norway Guang Zeng United Kingdom Jan Eiof Jonson Norway Jacek Kaminski United Kingdom Ian MacKenzie United Kingdom Elina Marmer European Community iv Chapter 6: Summary Coordinating lead authors Terry Keating United States André Zuber European Community Contributing authors Leonard Barrie Switzerland Daniel Jacob United States Rudolf Husar United States Glynis Lough United States Other contributors Jill Engel-Cox United States Brendan Kelly Switzerland Oystein Hov Norway Reviewers and commentors May Ajero Philippines Jan Eiof Jonson Norway Markus Amann Austria Glynis Lough United States Tami Bond United States Denise Mauzerall United States Mian Chin United States Hideaki Nakane Japan Jack Fishman United States Michael Sanderson United Kingdom Richard Honrath United States Thomas Trickl Germany Participants in Reading Review Meeting José Adame Spain Randall Martin Canada May Ajero Philippines Frederik Meleux France Hajime Akimoto Japan Loretta Mickley United States Joana Alves Finland Hideaki Nakane Japan Markus Amann Austria Stuart Penkett United Kingdom Soheila Amin-Hanjani United Kingdom Nicola Pirrone Italy Tami Bond United States Kirsty Pringle United Kingdom Gregory Carmichael United States Keith Puckett Canada Owen Cooper United States Pavan Racherla United States Kees Cuvelier European Community Kristin Rypdal Norway Ruth Doherty United Kingdom Michael Sanderson United Kingdom Sergey Dutchak Russian Federation Rich Scheffe United States Ahmed Elseoud Ahmed Egypt Martin Schultz Germany Magnuz Engardt Sweden Reiko Sodeno Japan Mathew Evans United Kingdom Alexandr Soloviyanov Russian Federation Giovanna Finzi Italy David Streets United States Johannes Flemming United Kingdom Vanisa Surapipith Thailand Susan Gardner United States Christiane Textor France Savitri Garivait Thailand Galina Tolkacheva Uzbekistan Arno Graff Germany Kjetil Tørseth Norway Dara Hang Cambodia John vanAardenne European Community Ian Hedgecock Italy Milan Vana Czech Republic Daniel Jacob United States Judit Varga Hungary Liisa Jalkanen Switzerland Guus Velders Netherlands Gerlinde Jung Italy Marta Vivanco Spain Terry Keating United States Oliver Wild United Kingdom Brendan Kelly Switzerland Simon Wilson Netherlands Carrie Lillyman Canada Guang Zeng United Kingdom Glynis Lough United States André Zuber European Community v TABLE OF CONTENTS Page List of tables...........................................................................................................................................x List of figures.........................................................................................................................................xi Acronyms and abbreviations...............................................................................................................xiv Executive Summary..............................................................................................................................1 Major findings...........................................................................................................................1 Key processes driving intercontinental transport........................................................1 Estimates of source-receptor relationships..................................................................1 Future changes.............................................................................................................3 Necessity of further research........................................................................................3 Recommendations......................................................................................................................3 Key challenges..............................................................................................................3 Role of the Task Force..................................................................................................4 References..................................................................................................................................4 Chapter 1 Introduction................................................................................................................5 Chapter 2 Conceptual overview of hemispheric or intercontinental transport processes......................................................................................................................8 2.1 Major emissions regions...............................................................................................8 2.2 Source-receptor relationships.....................................................................................11 2.3 Major types of intercontinental transport processes...................................................12 2.3.1 General circulation regimes.............................................................12 2.3.2 The mid-latitude cyclone airstreams................................................14 2.3.3 Deep convection...............................................................................15 2.3.4 Diffuse or small scale atmospheric boundary layer venting............16 2.3.5 Slow, low altitude flow.....................................................................16 2.4 Impact of intercontinental transport pathways on global and local pollution distributions................................................................................................................17 2.4.1 Impact of large-scale export events..................................................17 2.4.2 Contribution to background pollution..............................................19 2.4.3 Feedbacks between transported air pollutants and regional climate and meterology......................................................19 2.5 Impact of climate change on future intercontinental transport patterns.....................20 2.6 Outstanding issues and recommendations..................................................................21 2.6.1 Basic transport mechanisms.............................................................21 2.6.2 Modelling.........................................................................................21 2.6.3 Measurement networks.....................................................................22 References...............................................................................................................................22 Chapter 3 Observational evidence and capabilities related to hemispheric or intercontinental transport.......................................................................................29 3.1 Introduction................................................................................................................29 3.2 Long-range transport of ozone and its precursors......................................................30 3.2.1 The view from satellites....................................................................30 vi Page 3.2.2 Evidence for ozone and precursor transport from in situ measurements........................................................................31 3.2.3 Long-term trends in background ozone............................................35 3.2.4 Summary, remaining uncertainties and future needs.......................37 3.3 Long-range transport of aerosols and their precursors...............................................37 3.3.1 In situ and lidar observation of pollutant aersol outflow from continents.................................................................................37 3.3.2 Observations of pollutant aerosol in continental inflow..................38 3.3.3 Long-term record of aerosol transport across ocean basins...........41 3.3.4 Quantitative estimates of total pollution aerosol transport from satellite.....................................................................................42 3.3.5 Summary, remaining uncertainties and future needs.......................42 3.4 Concentrations seen at downwind receptor locations and implications for surface air quality in those regions.............................................................................44 3.4.1 Ozone concentrations.......................................................................44 3.4.2 Aerosol concentrations.....................................................................45 3.4.3 Summary, remaining uncertainties and future needs.......................47 3.5 Observational evidence for attribution of source regions...........................................49 3.5.1 Inverse modelling of emissions from satellite data sets...................49 3.5.2 Summary, remaining uncertainties and future needs.......................51 3.6 Ability to track long-term trends in hemispheric transport from existing surface observations...................................................................................................52 3.6.1 Characterization of ozone trends.....................................................53 3.6.2 Characterization of trends in dust transport....................................53 3.6.3 Characterization of trends in transport of sulfate and nitrate aerosol..............................................................................................54 3.6.4 Summary, remaining uncertainties and future needs.......................56 3.7 Concluding remarks....................................................................................................56 3.7.1 Surface site needs.............................................................................57 3.7.2 Vertical profiling needs....................................................................58 3.7.3 Satellite data needs...........................................................................59 3.7.4 Intensive campaign needs.................................................................60 References...............................................................................................................................60 Chapter 4 Emissions inventories and projections for assessing hemispheric or intercontinental transport.......................................................................................65 4.1 Introduction................................................................................................................65 4.2 Present-day emissions inventories..............................................................................66 4.2.1 Global inventories and databases....................................................66 4.2.2 Regional and national inventories and databases...........................69 4.3 Uncertainties and verification of present-day emission inventories...........................70 4.3.1 Quantification of uncertainties.........................................................70 4.3.2 Intersection of inventories with observations and modelling...........71 4.3.3 Important and uncertain sources.....................................................71 vii Page 4.4 Projection of future emissions....................................................................................72 4.4.1 Driving forces...................................................................................72 4.4.2 Methods............................................................................................75 4.4.3 Future emission inventories.............................................................75 4.5 Natural emissions.......................................................................................................77 4.6 Harmonization of different inventories......................................................................78 4.7 Recommendations......................................................................................................79 References...............................................................................................................................80 Chapter 5 Regional, hemispheric and global modelling.........................................................83 5.1 Modelling methods for diagnosing or quantifying transport......................................83 5.1.1 Methods for calculating source-receptor relationships...................85 5.1.2 The role of model intercomparisons.................................................86 5.1.3 The HTAP intercomparison..............................................................88 5.2 Estimates of ozone transport and its precursors.........................................................92 5.2.1 The global tropospheric ozone budget and surface ozone...............92 5.2.2 Previous studies of ozone and precursor transport..........................92 5.2.3 Present-day source-receptor relationships for ozone......................93 5.2.4 Ozone exceedance............................................................................99 5.2.5 Present-day source-receptor relationships for ozone columns......100 5.3 Estimates of transport of aerosols and their precursors............................................101 5.3.1 Introduction....................................................................................101 5.3.2 Analysis of results from AeroCom relevant for hemispheric transport of air pollution................................................................103 5.3.3 HTAP model simulations of hemispheric transport.......................104 5.4 Impact of hemispheric transport of nitrogen deposition...........................................108 5.5 Source-receptor relationships using idealized carbon monoxide tracers..................110 5.6 Regional source-receptor studies..............................................................................112 5.7 Suitability of current models....................................................................................114 5.8 Future changes in source-receptor relationships......................................................117 5.8.1 Influence of anthropogenic changes in emissions..........................117 5.8.2 Influence of climate change............................................................117 5.9 Summary and recommendations – the road forward................................................118 5.9.1 Current status.................................................................................118 5.9.2 Priorities for future model studies..................................................120 References.............................................................................................................................121 Chapter 6 Initial answers to policy-relevant science questions............................................128 References.............................................................................................................................138 viii APPENDICES Page Appendix A Activities of the Task Force on Hemispheric Transport of Air Pollution.........139 A.1 Formation of the Task Force.................................................................................................139 A.2 Task Force meetings..............................................................................................................140 A.3 Scientific workshops.............................................................................................................140 A.4 Websites and listservers........................................................................................................141 A.5 Assessment reports 2007 and 2009.......................................................................................141 A.6 HTAP model intercomparison...............................................................................................141 A.7 Support by Convention bodies..............................................................................................142 A.8 Outreach activities.................................................................................................................143 Appendix B Glossary of transport-related terms and definitions...........................................144 References..........................................................................................................................................146 ix