Office Phone: 301-405-5396
Office Address: 2403 Computer & Space Sciences Building
 Group Website



  • B.S., Applied and Engineering Physics, 1981, Cornell University
  • Ph.D., Applied Physics, 1987, Harvard University
  • Postdoctoral Fellow and Research Associate, 1988 to 1994, Harvard University

 Professional Experience

  • Department of Chemistry and Biochemistry, Department of Atmospheric and Oceanic Sciences, and Earth System Science Interdisciplinary Center, University of Maryland, 2007 to present.
  • Visiting Faculty Associate, California Institute of Technology, 2005 to 2007.
  • Research Scientist, NASA Jet Propulsion Laboratory, 1994 to 2007.

Research Interests

Quantification of the effects of human activity on the composition of Earth’s atmosphere by the development of computer models used to analyze a wide variety of observations. Focus on stratospheric ozone depletion and recovery, air quality, climate change, and the global carbon cycle. Participant in numerous atmospheric chemistry field campaigns and Earth Observing Satellite missions, including the upcoming Convective Transport of Active Species in the Tropics (CONTRAST) field campaign occurring in Guam during Jan and Feb 2014.

Professional Societies

  • American Association for the Advancement of Science
  • American Chemical Society
  • American Geophysical Union

 Major Recognitions and Honors

  • Highly Cited Researcher in Geosciences, Institute of Scientific Information Thompson Scientific, recognizing the 250 most cited researchers in the field of geosciences during the past 20 years.
  • Yoram J. Kaufman Award for Unselfish Cooperation in Research, presented by the Atmospheric Sciences Section of the American Geophysical Union, February 2009.
  • NASA Exceptional Achievement Medal, June 2007 for “exceptional contributions to the WMO/UNEP Ozone Assessment Report” and May 1999 for “crucial contributions to the evaluation of stratospheric models used in environmental assessment”.
  • Author, co-author, contributor and reviewer of various WMO/UNEP Scientific Assessment of Ozone Depletion reports and IPCC Climate Change reports that were recognized with the 2007 Nobel Peace Prize.

Significant Professional Service and Activities

  • Air Quality Control Advisory Council, Maryland Department of the Environment
  • University Park Community Solar LLC, Board Member
  • Small Town Energy Program for University Park, Advisory Committee
  • Sustainable Maryland Certified, Planning and Built Environment Task Force
  • Frequent guest speaker at community schools, environmental summits, and townhall meetings

Students Mentored

Close collaboration with a dozen graduate students (co-authorship of papers in the peer reviewed literature that were part of the student’s Ph.D. dissertation) at Caltech, University of Colorado, Harvard, and University of Maryland as well as supervision of research studies of 4 postdoctoral fellows. Have served on final PhD examination committee and / or dissertation prospectus review committee of more than a dozen students at UMd. Presently supervising the research of 4 graduate students at UMD.


Our research focuses on the quantification of the effects of human activity on atmospheric composition by developing computer models used to analyze a wide variety of observations, with a focus on atmospheric chemistry, air quality, climate change, and the global carbon cycle.

GV Take Off

Atmospheric Chemistry. We led an atmospheric chemistry field campaign called the Convective Transport of Active Species in the Tropics (CONTRAST) based in Guam during Jan and Feb 2014 that was designed to quantify how convection redistributes atmospheric compounds. The most extensive deep clouds in Earth’s climate system develop in the Tropical Western Pacific (TWP) during northern hemisphere winter. These clouds pack sufficient energy that, on occasion, they punch through the boundary that separates the lowest atmospheric layer (the troposphere) from the overlying stratosphere. Observations from three aircraft are being used to characterize the photochemical budget of tropospheric and stratospheric ozone, quantify the importance of biogenic bromine and iodine compounds for the chemistry of the tropical atmosphere, and assess the importance of various transport pathways from the ocean surface to the tropopause

Air Quality. Elevated levels of tropospheric ozone cause respiratory problems linked to increased morbidity and mortality in humans as well as significant damage to crops and plants. High levels of surface ozone are caused by nitrogen oxides and hydrocarbons released in the exhaust of power plants, factories, and vehicles. Our research effort is focused on the analysis of satellite and aircraft observations of atmospheric composition, using regional air quality models such as CMAQ and CAMx, to provide the scientific basis for policy decisions focused on achieving stringent, future air quality standards. We recently showed that elevated ozone on hot summer days in the mid-Atlantic is partially caused by pollution from power station peaking units utilized to meet unusually high demand for electricity during the warmest days of summer (He et al., GRL, 2013) and that emissions of nitrogen oxides from automobiles in the Baltimore-Washington metropolitan region are likely overestimated, by nearly a factor of two, in emission inventories used to drive air pollution assessments by the U.S. Environmental Protection Agency (Anderson et al., Atmos. Envir., 2014). Our research efforts are closed related to air quality control efforts.

Climate Change. Surface temperature responds to a variety of natural and anthropogenic forcings, including warming due to rising levels of greenhouse gases (GHGs). We have developed a model that tracks the influence on global temperature of GHGs, volcanic and industrial aerosol particles, the 11 year variation in total solar irradiance, the temporary heat exchange between the ocean and atmosphere due to phenomena known as the El Niño Southern Oscillation and the Atlantic Meridional Overturning Circulation, as well as long-term export of atmospheric heat to the world’s oceans (Canty et al., ACP, 2013). We are using this model to quantify the human influence on past increases in global temperature, to constrain future rises in global temperature, and to evaluate the efficacy of a proposed idea to mitigate climate change via the injection of sulfate to Earth’s stratosphere (also known as geo-engineering of climate). This model has also been used to suggest that major volcanic eruptions may have considerably smaller effect on global climate than commonly thought.

Carbon Cycle.
Carbon dioxide (CO2) is the greatest waste product of modern society. About half of the CO2 released by human activity is taken up by the world’s oceans and terrestrial biosphere. The precise location and magnitude of these carbon sinks is unknown, yet of enormous importance for defining interactions within the global carbon cycle that might be altered by climate change. Quantification of these carbon sinks is also vital for future management of the global carbon cycle. We helped design a NASA satellite mission, the Orbiting Carbon Observatory (OCO-2), that launched successfully on 2 July 2014. It is expected that data from OCO-2 will revolutionize the understanding of the global carbon cycle by watching Earth’s biosphere breathe from the vantage point of space. Our students are also analyzing measurements of CO2 and CH4 acquired locally via the Fluxes of Atmospheric Greenhouse Gases in Maryland (FLAGG-MD) project.

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