January 21st, 2013
Meiyun Lin, Arlene M. Fiore, Owen R. Cooper, Larry W. Horowitz, Andrew O. Langford, Hiram Levy II, Bryan J. Johnson, Vaishali Naik, Samuel J. Oltmans, Christoph J. Senff. Journal: Journal of Geophysical Research. DOI:10.1029/2012JD018151
Stratosphere-to-troposphere transport of ozone is a common occurrence at mid- and high latitudes, but its influence on tropospheric ozone levels remains a long-standing question, despite decades of research. GFDL scientists and colleagues analyzed balloon soundings, lidar, surface and satellite measurements using GFDL’s new global high-resolution chemistry-climate model, to look at the extent to which naturally occurring stratospheric ozone intrusions reach the surface and affect air quality.
The team found that stratospheric ozone intrusions can episodically increase ground-level ozone by 20-40 ppb in parts of the western United States and directly lead to episodes of high-ozone in excess of EPA’s health-based limit (75 ppb). Evidence is found for 13 such events from April to June 2010, in notable contrast to prior work concluding that stratospheric influence in surface air is rare.
These estimates are up to 2-3 times greater than previously reported. The findings imply that naturally occurring stratospheric intrusions may pose a challenge for springtime ozone over the U.S. Mountain West to stay below federal limits with domestic emission controls.