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 Convective Transport of Active Species in the Tropics (CONTRAST) field campaign that was conducted in Guam during Jan and Feb 2014.
Major Recognitions and Honors
Significant Professional Service and Activities
Presently supervising the research of 8 graduate students at UMD who are working on a wide range of research topics related to atmospheric chemistry and climate. In the past have had close collaboration with a dozen graduate students at Caltech, University of Colorado, and Harvard as well as supervision of research studies of 4 postdoctoral fellows.
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.
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 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.