NASA Reference Publication 1400

1997

Atmospheric Effects of Subsonic Aircraft: Interim Assessment Report of the Advanced Subsonic Technology Program

Edited by:

Randall R. Friedl NASA Headquarters Washington, D. C.

National Aeronautics and Space Administration

Goddard Space Flight Center Greenbelt, Maryland 20771 1997 Contributing Authors

Dr. Randall R. Friedl Dr. Steven L. Baughcum NASA Jet Propulsion Laboratory Boeing Company Pasadena, California Seattle, Washington

Dr. Bruce E. Anderson Dr. John Hallett NASA Langley Research Center Desert Research Institute Hampton, Virginia Reno, Nevada

Dr. Kuo-Nan Liou Dr. Philip J. Rasch University of Utah National Center for Atmospheric Research Salt Lake City, Utah Boulder, Colorado

Dr. David H. Rind Dr. Kenneth Sassen NASA Goddard Space Flight Center University of Utah Goddard Institute for Space Studies Salt Lake City, Utah New York, New York

Dr. Hanwant B. Singh Dr. Leah R. Williams NASA Ames Research Center SRI International Moffett Field, California Menlo Park, California

Dr. Donald J. Wuebbles University of Illinois Urbana, Illinois

This publication is available from the NASA Center for AeroSpace Information, 800 Elkridge Landing Road, Linthicum Heights, MD 21090-2934, (301) 621-0390. ATMOSPHERIC EFFECTS OF SUBSONIC AIRCRAFT: INTERIM ASSESSMENT REPORT OF THE ADVANCED SUBSONIC TECHNOLOGY PROGRAM

Table of Contents

EXECUTIVE SUMMARY ...... v

1. INTRODUCTION ...... 1

, AIRCRAFT EMISSIONS ...... 5 2.1 Emissions Characteristics ...... 5 2.1.1 Gaseous Emissions ...... 5 2.1.2 Particle Emissions ...... 7 2.2 Global Inventory Methodologies ...... 9 2.3 1992 Emission Inventories ...... 10 2.4 Uncertainties in Aircraft Emission Inventories ...... 11 2.4.1 Simplifying Assumptions ...... 12 2.5 Future Trends and Methodology for Constructing Long-Range Forecasts ...... 14 2.6 Summary ...... 15

. UNDERSTANDING THE EFFECTS OF AIRCRAFT EMISSIONS ...... 27 3.1 Near-Field Effects ...... 27 3.2 Regional and Global-Scale Effects ...... 29 3.2.1 Perturbations to Ambient Levels ...... 29 3.2.1.1 NOx ...... 29 3.2.1.2 CO2, CO, and Hydrocarbons ...... 31 3.2.1.3 H20 ...... 32 3.2.1.4 Soot ...... 32 3.2.1.5 Sulfate ...... 33 3.2.2 Ozone Chemistry ...... 35 3.2.2.1 Ozone Tendencies Relative to NOx ...... 35 3.2.2.2 Role of Non-Methane Hydrocarbons ...... 36 3.2.2.3 Heterogeneous Chemistry ...... 36 3.2.2.4 Ozone Trends ...... 39 3.2.3 Radiative Forcing ...... 40 3.2.3.1 Clear Sky Effects ...... 41 3.2.3.2 Direct Cloud Effects of Contrails ...... 41 3.2.3.3 Indirect Cloud Effects of Contrails ...... 43 3.2.3.4 Cirrus Cloud Trends ...... 44 3.3 Summary ...... 44

iii . MODELING THE GLOBAL EFFECTS OF AIRCRAFT EMISSIONS ...... 57 4.1 Global Modeling Characteristics ...... 58 4.1.1 Model Types ...... 59 4.1.2 Assessment Model Requirements ...... 60 4.2 Effects on Atmospheric Chemistry ...... 61 4.2.1 Description of Modeling Tools ...... 62 4.2.1.1 IMAGES Model ...... 62 4.2.1.2 Harvard/GISS Model ...... 63 4.2.1.3 GMI Core Model ...... 64 4.2.2 Evaluation of Models ...... 65 4.2.2.1 Evaluation of Chemical Mechanisms ...... 65 4.2.2.2 Rn Tracer Study: Evaluation of Rapid Vertical Transport Near the Ground ...... 67 4.2.2.3 NOy Tracer Study: Evaluation of Large-Scale Transport in the Upper Troposphere ...... 71 4.2.2.4 Comparison of IMAGES and Harvard Models with Observations ...... 74 4.2.3 Sensitivity Studies ...... 77 4.2.3.1 Description of the Experiments ...... 77 4.2.3.2 Model Results and Discussion ...... 78 4.3 Effects on Climate ...... 82 4.3.1 Description of Modeling Tools ...... 82 4.3.1.1 Description of Models ...... 82 4.3.1.2 Description of Modeling Techniques ...... 83 4.3.2 Climate Sensitivity Studies ...... 83 4.3.2.1 Layered vs. Well-Mixed Forcing and GWP ...... 83 4.3.2.2 Aircraft Water Vapor Emissions ...... 84 4.3.2.3 Aircraft-Induced Ozone Changes ...... 85 4.3.2.4 Aircraft Soot Emissions ...... 86 4.3.2.5 Aircraft Contrail Simulati