Steven Hanna

Adjunct Associate Professor of Environmental Health

Department of Environmental Health

Landmark Center, Room 404J
401 Park Drive
Boston, Massachusetts 02215
Phone: 207.967.4478


Ph.D., M.S., B.S.          Meteorology, Penn State University (1967, 1966, 1964)


April 2002-Present: Adjunct Associate Professor, Harvard School of Public Health, Boston, MA
July 1997- July 2003: Research Professor, George Mason University, Fairfax, VA
April 1997-Dec. 2000: Research Associate, Harvard School of Public Health, Boston, MA
April 1997-Present: President, Hanna Consultants, Kennebunkport, ME
1992-April 1997: Principal Meteorologist, Earth Tech, Inc., Concord, MA
1985-1992: Founder and Vice President, Sigma Research Corp., Westford, MA
1981-1985: Principal Meteorologist, Environmental Research & Technology, Inc.(ERT), Concord, MA
1967-1981: Research Meteorologist and Acting Director (1979-1981) USDOC/NOAA, Environmental Research Laboratories, Atmospheric Turbulence and Diffusion Laboratory, Oak Ridge, TN


Dr. Hanna is the 1994 recipient of the American Meteorological Society’s Award for Outstanding Contribution to the Advance of Applied Meteorology, and is a 1996 Centennial Fellow of the College of Earth and Mineral Sciences of Penn State University. On June 2, 2003, he testified at a Congressional hearing on the subject of “Following Toxic Clouds: Science and Assumptions in Plume Modeling.”  In January, 2005, he was named a Fellow of the American Meteorological Society.  In January 2010, he received the AMS Helmut E. Landsberg award for “Significant novel and insightful contributions in applied meteorology and urban studies, including field work, data interpretation, model development, and model evaluation.”

Professional Summary

Dr. Hanna is a specialist in atmospheric turbulence and dispersion, in the analysis of meteorological and air quality data, and in the development, evaluation, and application of air quality models.  He is an AMS Certified Consulting Meteorologist with over 40 years of experience.  He has led several research and development projects involving, for example, the analysis of uncertainties of dispersion models, the statistical evaluations of hazardous gas dispersion models and regional ozone models, the development of models for the dispersion of emissions from tall power plant stacks, from offshore oil platforms, and from accidental and intentional releases of hazardous chemicals, and the analysis of data from large urban and regional field experiments.  From 1988-1997, Dr. Hanna was Chief Editor of the Journal of Applied Meteorology, and has published 140 articles in refereed journals, six chapters in books, and five books in which he is the primary author.

Related Professional Experience

Model Evaluation, Model Uncertainty, and Concentration Fluctuations

Under support of the American Petroleum Institute, a statistical method for evaluating air quality models was developed and applied to many types of source scenarios, models, and field data sets. This method is now accepted as a standard in international research on dispersion model evaluation.   The U.S. Air Force, the U.S. Army, and the American Petroleum Institute supported the further development of a framework for evaluating and for estimating the uncertainty in environmental models. During the past few years, the Department of Defense, the Department of Energy, and the Department of Homeland Security have sponsored additional studies of model evaluation methods, with emphasis on scenarios where chemical or biological agents might be released.

From 1993 through 2006, the Electric Power Research Institute supported the development of uncertainty analysis methods for photochemical grid models.  The Nuclear Regulatory Commission has had Dr. Hanna review their uncertainty analysis methods for linked emissions-dispersion-exposure-risk consequence models. The American Petroleum Institute has had Dr. Hanna lead a long-term study in which the uncertainties of dispersion models for toxic gases in urban areas were investigated.  In November 2006, Dr. Hanna presented an invited talk on air quality model uncertainty at an EPA workshop on uncertainties in estimation of future changes in air quality due to changes in climate.

From 2004 through 2007, Dr. Hanna was a lead scientist in a Defense Threat Reduction Agency (DTRA) study involving improvements of methods to account for mesoscale and regional-scale uncertainties in transport and dispersion estimates.

Dr. Hanna is currently leading model evaluation efforts for the HPAC-Urban model and for Rockle-type urban models (supported by DTRA), for the JEM model (supported by DOD), and for the LATRA3D model (supported by the USAF).

Regional Air Quality Data Analysis and Model Evaluation

Dr. Hanna was the chief scientist for analysis of field data from several regional and urban-scale ozone experiments, including the South Central Coastal Cooperative Aerometric Monitoring Program (SCCCAMP), the Lake Michigan Ozone Study (LMOS), and the Gulf of Mexico Air Quality Study (GMAQS).  He was the manager and chief scientist for the multi-agency Cross-Regional Model Evaluation (CReME) project, in which four regional air quality models were evaluated with field data from the LMOS, Northeast, and SARMAP domains.  From 1999 through 2005, Dr. Hanna was the chief scientist on two DOI/MMS-sponsored studies involving boundary layers and air quality in the Gulf of Mexico.

Dr. Hanna led a ten-year effort in which the effects of uncertainties in input parameters on the uncertainties in predictions of regional air quality models were assessed using Monte Carlo methods.  In 2005, Dr. Hanna completed a study of the uncertainties in the BEIS3 model, which is used to estimate biogenic emissions for input to photochemical grid models. He led a Monte Carlo uncertainty study of model predictions of benzene and 1,3-butadiene in the Houston area.

Modeling of Turbulence and Diffusion

Dr. Hanna has developed applied diffusion models for several industrial and governmental clients, including a diffusion model for complex terrain (RTDM) for the Westvaco Corporation, a model for overwater diffusion (OCD) for the Minerals Management Service, a cooling tower plume model (ATCOOL) for the Department of Energy (DOE), a model for diffusion from tall stacks (HPDM) for EPRI, a hazardous gas model for chemical reactions and thermodynamics associated with UF6 releases, and a baseline urban dispersion model.

In the past five years, Dr. Hanna’s simple urban baseline dispersion model was further enhanced for use in estimating impacts of possible terrorist attacks with chemical and biological agents. It was evaluated with field data from Los Angeles, Salt Lake City, Oklahoma City, and New York City.  He is leading the evaluation of DTRA’s HPAC-Urban model with field data from Oklahoma City and New York City.  He was the chief scientist of the Madison Square Garden-2005 (MSG05) tracer experiment in New York City. He is currently leading analysis of the comprehensive set of urban field experiments and has developed and evaluated a simple urban dispersion model.

Hazardous Gas Model Development and Analyses

The AIChE sponsored the writing of the Guidelines for use of Vapor Cloud Dispersion Models in 1987, and the preparation of greatly-enhanced second edition in 1996.   The AIChE also sponsored preparation of the 2002 book entitled Wind Flow and Vapor Cloud Dispersion at Industrial and Urban Sites.

A USAF/API study was completed in which 15 hazardous gas models were evaluated with data from 8 field studies.

An industry-government consortium supported the five-year PERF 93-16 Dispersion Modeling Project, including field and laboratory experiments, in which dense gas models were improved so that they account for high surface roughnesses, short-duration releases, and stable ambient conditions.  Dr. Hanna was responsible for the planning and coordination of the technical components of the project and carried out the analysis of the Kit Fox field data and the evaluation of the HGSYSTEM 3+ model.

From 2005 through the present, Dr. Hanna has led DARPA, DHS, DTRA, and Chlorine Chemistry Council studies of emissions and dispersion of chlorine released from railcars.  In the DTRA study, source emission model improvements have been made for Toxic Industrial Chemicals (TICs) and the improved models will be employed in the HPAC modeling system.

Hazardous Gas Modeling for DTRA, DOE-CBNP, and DHS

From 1997-2002, Dr. Hanna was the director and chief scientist of the Coordinated Hazardous Atmospheric Release Modeling (CHARM) project at George Mason University.  The research, supported by the Defense Threat Reduction Agency (DTRA), was concerned with development and evaluation of mesoscale meteorological models and atmospheric dispersion models for releases of chemical and biological agents. Dr. Hanna is continuing this research while at Harvard.  Also, from 2000 through the present, DHS is supporting studies focused on improvements in guidance given to emergency responders concerning transport and dispersion in urban areas.

Reviews of Diffusion Research

Dr. Hanna has been requested to prepare written reviews of various aspects of diffusion research by many national and international agencies, industries, and universities.  He is a member of peer-review panels for NRC, DOE, EPA, CDC, DHS, CARB, and DOD programs.  In March, 1997, he chaired the Peer Review Panel for the Atmospheric Modeling Division of the EPA National Exposure Research Laboratory.  In June, 2000, he was a member of the Peer Review Panel for the EPA research program on ozone and air toxics.   In November, 1997, he chaired the Peer Review Panel for the U.S. modeling program for the Khamisiyah, Iraq, chemical releases.  In 1998 he chaired the Peer Review Panel for the EPA’s new AERMOD model.  In 2000, he was member of the Peer Review Panel for the Army Research Office’s Atmospheric Boundary Layer Program.  In 2003, he was a reviewer of the DOE VTMX research program. In 2005, he was a reviewer of the DTRA Chemical/Biological Defense Science Program. In 2009, he gave a keynote address at the Workshop on Evaluations of IMAAC models (for DHS).

Teaching Experiences at Universities

Dr. Hanna has been an adjunct professor and/or research professor at several universities during his career (Vanderbilt University from 1969 through 1973, University of Tennessee from 1974 through 1981, Harvard School of Public Health from 1983 through the present, and George Mason University from 1997 through 2002).  Approximately once each year throughout this period, he has taught graduate-level courses in atmospheric turbulence and dispersion. The Vanderbilt and UT lectures were used as the basis for the textbook by Hanna, Briggs, and Hosker (1982), which has been widely adopted as a basic text at other universities.  In addition, three or four times a year from 1987-1997, Dr. Hanna taught a two-day short course entitled “Vapor Cloud Dispersion” as part of AIChE conferences.  Since 2002, he has taught 8 to 16 lectures a year in Air Quality Meteorology graduate-level courses at HSPH in Boston and in their International Institute in Cyprus.

From 1997 through 2003, Dr. Hanna organized and ran the annual GMU July Workshop on Atmospheric Transport and Dispersion Modeling.

Business Experience

In 1985, Dr Hanna was a co-founder of Sigma Research Corporation, which carried out basic and applied research on meteorology and air quality issues for a variety of clients.  The company grew successfully and was purchased by Earth Tech in 1992.  Since 1997, Dr. Hanna has continued his consulting under Hanna Consultants, and spends half-time on that effort.  The other half of his time was spent at George Mason University (from 1997-2002) and at Harvard School of Public Health (from 2003-present). Hanna Consultants projects are sponsored by government agencies, chemical industries, environmental consulting companies, industrial associations, and universities.

Expert Witness

Dr. Hanna has provided testimony in depositions in several litigation cases and has testified in two trials.  In most of these cases, he was required to apply and interpret atmospheric transport and dispersion models.  He has modeled releases of methyl mercaptan, ammonia and chlorine from rail cars, oleum from valve ruptures, ammonia from a tank rupture, sulfuric acid from a stack, hydrogen sulfide from a missile spill, water vapor and particulates from paper mills and cooling towers, small particles and ozone from power plants over the eastern U.S., and wind flows in Manhattan street canyons.

On June 2, 2003, Dr. Hanna was one of seven scientists invited to testify at a hearing before the U.S. Congress’ Subcommittee on National Security, Emerging Threats, and International Relations, on the subject of “Following Toxic Clouds: Science and Assumptions in Plume Modeling.”

Professional Organizations

Sigma Xi, AAAS, AWMA
AMS:    Chief Editor, J. Appl. Meteorol., 1988-1997
Chairman, Atmos. Turb. and Diff. Committee, 1977-1978
Member, AMS/EPA Cooperative Work Group, 1979-1981
Member, AMS Board on Urban Meteorology, 2002-2009
Co-Chairman of Urban Environment Conference in 2004 (Vancouver) and 2006 (Atlanta)
Chairman, 1974 Atmos. Turb. and Diff. Conference, Santa Barbara
Recipient of 1994 AMS Award for Outstanding Contribution to the Advance of Applied
AMS Certified Consulting Meteorologist (Number 361)
Fellow, 2005
Co-Chairman of 2006 Forum on Managing our Physical and Natural Resources:
Successes and Challenges, Annual Meeting, Atlanta
Chairman of F.A. Gifford Memorial Session at AMS Annual Meeting, 2008
Recipient of 2010 AMS Helmut E. Landsberg Award for “Significant novel and insightful
contributions in applied meteorology and urban studies, including field work, data
interpretation, model development, and model evaluation”