Photochemical ozone production near the Earth's surface is considered to be a summertime, urban phenomenon. However, air-quality measurements in the rural Upper Green River basin, Wyoming, show rapid, diurnal photochemical production of ozone when air temperatures are as low as -17 °C. The image shows the Jonah natural gas field in Green River valley near the town of Pinedale on 12 May 2006. Photos by EcoFlight (www.ecoflight.info), courtesy of SkyTruth (www.skytruth.org).
Letter p120; News & Views p88; Backstory p152