Temporal variability of summer‐time ozone and aerosols in the free troposphere over the eastern North Atlantic

In the free troposphere over Tenerife in the summer, O 3 concentrations are anti‐correlated with major pollutant aerosols (nss‐SO = 4 and NO − 3 ) and with 210 Pb, a tracer for boundary layer sources. In contrast, O 3 is highly correlated with 7 Be, a product of cosmic ray interactions in the upper troposphere and stratosphere. This suggests that natural O 3 sources (i.e. the stratosphere) might be playing an important role. Nonetheless our results do not preclude the possibility that substantial amounts of pollution‐related O 3 could be transported in the free troposphere. However, to be consistent with our results, the transport mechanisms would have to incorporate efficient processes for the removal of pollutant aerosol species and 210 Pb.