Maximum daily 8-hr average ozone mixing ratio (MDA8) in ppb (blue), smoothed (24 hour running mean) wind speed in m/s (orange), temperature in °C (green), and snow depth in inches (black) at Boulder, WY during winters 2008 – 2013. The National Ambient Air Quality of 75 ppb is shown by the blue horizontal line and the 0 °C temperature level is indicated by the horizontal green line. Note the high ozone events in 2008 and 2011 and low ozone winters of 2009, 2010, 2012 and 2013.