Improved Understanding of North American Background Ozone

EPA Grant Number: F13B10155
Title: Improved Understanding of North American Background Ozone
Investigators: Travis, Katherine Rose
Institution: Harvard University
EPA Project Officer: Lee, Sonja
Project Period: August 1, 2014 through August 1, 2016
Project Amount: $84,000
RFA: STAR Graduate Fellowships (2013) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Fellowship - Atmospheric Chemistry


Ozone pollution is a serious public health concern in the United States. Background ozone is not directly measurable and thus must be calculated from global chemical transport models (CTMs). There also are significant differences between CTMs in estimates of background ozone, which is very problematic for air quality policy. This research will evaluate the following hypotheses: (1) that background ozone in the United States can be elevated by a combination of influences including stratospheric intrusions, lightning, wildfires and foreign pollution; and (2) that improvements in CTM resolution, wildfire plume chemistry, biogenic emissions chemistry and anthropogenic emissions inventories can significantly improve the ability to quantify the ozone background, its variability and its contribution to National Ambient Air Quality Standards (NAAQS) exceedances.


After focusing on ozone production in the United States during the spring and summer of 2013, this project will use a new continental-scale version of GEOS-Chem with high horizontal resolution nested dynamically within the global model to develop a uniquely consistent representation of global and regional processes contributing to background ozone. High resolution is important for characterizing nonlinear chemistry, pollution plumes and local source variability. Nesting within a global model is critical for representing sources and transport outside North America. Key goals to achieve a successful model representation of U.S. ozone during this period include improved wildfire representation and betterconstrained chemistry of species emitted by vegetation, both areas of disagreement among CTMs. The results will be evaluated with a variety of surface ozone measurements and satellite observations, as well as the recent NASA SEAC4RS aircraft campaign in the southeast United States.

Expected Results:

This work will lead to significant improvement in (1) understanding the factors controlling background ozone in surface air over the United States, (2) quantifying this background for air quality policy application and (3) identifying exceptional events that might be considered exempt from the ozone NAAQS. This work will add to the understanding of background ozone over North America and assist the regulatory community in setting and achieving ambient air quality goals. The research on background ozone will uniquely connect air quality and climate issues. Through the work of the broader GEOS-Chem and atmospheric chemistry community, the capability of Earth System models will be enhance to better consider atmospheric chemistry as an agent for climate and biogeochemical forcings and feedbacks.

Potential to Further Environmental/Human Health Protection

This research will result in an improved understanding of North American background ozone. It will support regulatory development at both the EPA and state air quality agencies to better protect human health and welfare.

Supplemental Keywords:

ozone, GEOS-Chem, NAAQS

Progress and Final Reports:

  • 2015
  • Final