Air Pollution

Ozone in surface air in many locations reflects a balance of production from local-to-regional anthropogenic and natural sources and of transport.  We aim to quantify the relative contributions to ozone pollution, with a heavy focus on the United States.  Knowing the ‘break-down’ of sources contributing to surface ozone pollution is needed to set attainable standards and to implement effective pollution control policies.  Examples of ongoing research projects are included below.

Air quality and remote sensing

Air quality in India and China: Using satellite and surface observations, we aim to better understand the air quality problem in rapidly developing economies such as India and China. Projects include investigating the spatial and temporal variability in aerosol optical depth and particulate matter concentrations in India. [Dan Westervelt, Jean Guo, Xiaomeng Jin, Arlene Fiore]

OMI HCHO:NO2Observing surface ozone sensitivity from space: Determining the most effective strategy for mitigating local surface ozone pollution requires knowledge of the relative ambient concentration of NOx to VOCs in the atmosphere. We use satellite observations of the tropospheric column ratio of HCHO (a marker of VOCs) to NO2 (a marker of NOx) as an indicator to identify areas which would benefit from reducing NOx emissions, and areas where reducing VOC emission leads to lower ozone. [Xiaomeng Jin, Arlene Fiore, Lee Murray, Luke Valin]

Air pollution exposure maps for NYS: Collaborating with Dr. Patrick Kinney‘s group at Columbia University Mailman School of Public Health, NYSDEC and NYSDOH, we are developing multi-pollutant and long-term exposure maps for NYS using satellite, model and hospital admission data  to examine health benefits accrued over the past two decades due to the implementation of emission controls.  [Arlene Fiore, Xiaomeng Jin, Dan Westervelt]


Background ozone in surface air over the United States


A major research thrust involves quantifying “background” ozone (defined here as ozone concentrations in the absence of domestic anthropogenic emissions; see schematic above from the sidebar in Fiore et al., EM, 2014) in surface air and daily to decadal variability in the individual components contributing to background (i.e., ozone produced from global methane, from international anthropogenic emissions,  from natural biogenic and soil emissions or lightning NOx, and transported from the stratosphere).   Recent work includes comparing background ozone estimates from the GFDL AM3 and GEOS-Chem chemistry-transport models [Fiore et al., Atmos. Environ., 2014] and examining changes in U.S. surface ozone seasonal cycles associated with regional NOx emission reductions, rising global methane, and climate change [Clifton et al., 2014].  Please see our publications page for more details. [Olivia Clifton, Arlene Fiore].

Source attribution and meteorology during pollution episodes

We are contributing to a NASA Air Quality Applied Sciences Tiger Team activity to determine the relative contributions from emissions within a state versus from inter-state (regional) transport, and background contributions to the highest pollution levels over the eastern United States.   We are focusing on episodes during June 2007, June 2011, and June-July 2012 and using multi-year GEOS-Chem simulations to determine which aspects of these events are generalizable to events in other years.  The 2012 heat wave event serves as a benchmark against which we can gauge changes in air pollution and associated meteorology in a future, warmer climate simulated by chemistry-climate models [Olivia Clifton, Arlene Fiore, Nora Mascioli, George Milly, Lee Murray, Melissa Seto, Luke Valin]

Past changes and future projections in extreme ozone pollution events


Changes in regional NOx emissions as well as regional climate are expected to alter the frequency of high-ozone episodes.  Recent work [Rieder et al., 2013] uses methods from extreme value theory statistics to characterize changes over the eastern United States in recent decades.  We are currently extending those methods to determine how extreme ozone pollution is projected to change under several scenarios with the GFDL CM3 chemistry-climate model. [Harald Rieder (alumnus)]

Funding sources: EPA and NASA