Modeling trace gas budgets in the troposphere: 1. Ozone and odd nitrogen

A two‐dimensional photochemical model of the atmosphere has been used to calculate dynamical and chemical budgets in the troposphere. Model distributions of O 3 and NO y species are compared with observations. The seasonal variations of these species can be explained in terms of the variation of the different components of their budgets. Regional variations are apparent. In the northern hemisphere, where results represent a “mean” polluted troposphere, the O 3 budget is essentially a balance between net photochemical production and loss via dry deposition in the summer. The flux from the stratosphere plays an important role in the winter and early spring. In the southern hemisphere the flux of O 3 from the stratosphere again makes a significant contribution in the winter and spring. The chemical production is much reduced compared with the northern hemisphere. The NO y budget is a balance between NO x emissions and loss via wet and dry deposition of HNO 3 .