A 3D model is therefore limited in the length of time it can simulate. Typically, a 3D model is used to simulate periods of up to a year. The primary advantage of a 3D model compared to a 2D model is its more physically correct description of atmospheric transport processes. In a 2D model, mixing processes are parameterized as diffusion while in a 3D model, the atmospheric planetary wave breaking producing the mixing can be explicitly simulated. The percentage difference between the model prediction and the observation is shown in the bottom plot.
Total ozone is the integrated amount of ozone from the bottom to the top of the atmosphere.
It is typically measured in Dobson Units. A Dobson Unit can be thought of as the depth in hundreds of millimeters of the layer of ozone which would occur if all the ozone in the atmosphere were brought to standard pressure and temperature. The top plot of the satellite data reveals a number of details concerning seasonal changes in ozone. First, ozone is a minimum in the tropics and is largest at mid to high latitudes. Second, the hemispheric maxima in ozone occur in the spring.