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NCAR GV taking off from Guam airport, 19 Jan 2014, for Research Flight 4 of the NSF CONTRAST field campaign

Our research focuses on quantification of the effect of human activity on atmospheric composition.

We develop computer models that are used to analyze a wide variety of observations.  Our focus is on atmospheric chemistry, air quality, climate change, and the global carbon cycle.

Atmospheric Chemistry. Salawitch was co-lead of an atmospheric chemistry field campaign called CONTRAST, based in Guam, during Jan and Feb 2014.  CONTRAST, which stands fro CONvective TRansport of Active Species in the Tropics, 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.

Convective system as seen from the NCAR GV aircraft; photo by Rebecca Hornbeck.

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 will be used to characterize the photochemical budget of ozone including assessing the role of upwind biomass biomass in influencing the composition of the remote Pacific, 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 stratosphere.  More information is given at the CONTRAST website.

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 caused, in part, 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).   We also showed, based on analysis of data collected during the DISCOVER-AQ field campaign, that the emission of nitrogen oxides from automobiles for using the CMAQ and CAMx inventories is likely high, by nearly a factor of two (Anderson et al., Atmos. Envir, 2014).

NASA P3 aircraft during DISCOVER-AQ as seen from the UMCP RAMMPP aircraft; photo by Jeff Stehr.

The research findings of He et al. (2013) and Anderson et al. (2014) have important policy implications; the former suggest a significant component of the so-called climate penalty factor (the deterioration of air quality as temperature rises) can be ameliorated by legislation directed at reducing emission of NOx from peaking units that operate to meet the demand of electricity on during the dog days of summer; the latter suggests future efforts to improve air quality may not be beneficial if directed at cars, as the contribution of this sector to surface ozone is probably smaller than commonly thought.

Our current air quality efforts are focused on improving the representation of the chemistry of nitrogen oxides with both CMAQ and CAMx, assessing the role of emission of pollutants by ships in the Chesapeake Bay on local air quality, and assisting the Maryland Department of the Environment in preparing a State Implementation Plan that must be submitted to the U.S. Environmental Protection Agency.

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.  This model has also been used to suggest that major volcanic eruptions may have considerably smaller effect on global climate than commonly thought (Canty et al.):

Summary figure from Canty et al. (2013). Click here for more information.

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).

Global Carbon Cycle. Carbon dioxide (CO2) is the most important anthroogenic GHG and, quite literally, the single 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 vital for future management of the global carbon cycle. We are part of the NASA Orbiting Carbon Observatory (OCO-2) science team.

OCO-2 launched on 2 July 2014, ascended to it's lead spot on the NASA A-train in early August 2014, and will soon be producing observations of atmospheric CO2 that will revolutionize our understanding of the global carbon cycle.

Launch of OCO-2 on 2 July 2014, photographed by Stephen Kelly Sullivan from Malibu, California.

Finally, we are involved with a new CO2 aircraft campaign called FLAGG-MD (Fluxes of Atmospheric Greenhouse Gases in Maryland) sponsored by the U.S. National Institute of Standards and Technology.  FLAGG-MD will begin Fall 2014 and will be modeled after the highly successful INFLUX experiment.

Department of Atmospheric and Oceanic Science                                           College of Computer, Mathematical, and Natural Sciences

Department of Chemistry and Biochemistry                                                                                  The University of Maryland Newsdesk

Earth System Science Interdisciplinary Center                                                                                             The University of Maryland

This page last updated on Sunday, 24 August 2014