Skip to Content

Impacts of midlatitude precursor emissions and local photochemistry on ozone abundances in the Arctic and North America

We assess the relative impact of transport of pollution from midlatitudes and of natural emissions sources on the abundance of ozone in the Arctic and over North America using the GEOS-Chem global chemical transport model, together with satellite and in situ observations of tropospheric ozone and its gaseous precursors. The model reproduces well the seasonal cycle in the abundances of PAN and ozone as measured at the surface at Alert and during the summer in the Arctic free troposphere. Tagged regional tracers are used to construct a budget of ozone transported from midlatitude source regions, which contribute 25-35% of the ozone in the middle and upper Arctic troposphere in the summer, and adjoint sensitivity studies link the summer ozone distribution to specific sources. We introduce 4D-VAR inversions using ozonesonde data as a means to further refine the distribution of emissions at midlatitudes.