Evidence of significant large-scale impacts of boreal fires on ozone levels in the midlatitude Northern Hemisphere free troposphere

Summertime observations of O3 and CO made at the PICO-NARE station during 2001, 2003, and 2004 are used to assess the impact of boreal forest fires on the distribution of O3 mixing ratios in the midlatitude Northern Hemisphere (NH) lower free troposphere (FT). Backward trajectories were used to sele