Features of Polar Regions Relevant to Tropospheric Ozone Chemistry

It is becoming increasingly apparent that the polar regions play an important role in the atmospheric cycle of ozone. What is perhaps less well recognized is that this is true not only in the stratosphere (above 8 to 10 km) but also in the troposphere (0 to 8 km). The aim of this paper is to “set the scene” for the following discussions by describing characteristics of geography, climate and chemical environment in the Arctic and Antarctic that help us to understand polar tropospheric ozone. The use of “polar” here refers to those areas poleward of 40° latitude. This represents approximately 36% of the total surface area of the globe. 40° is chosen to include areas of the northern hemisphere that are frequented by arctic air masses during winter as indicated by the mean position of the arctic front in January (Figure 1).