Remote sensing of the middle atmosphere from Earth orbit has provided a wealth of two- and three-dimensional images over the last 15 years. Although these images have been powerful tools for testing chemical-dynamical models, they lacked high-horizontal spatial resolution. In contrast, high-altitude aircraft experiments provided high spatial resolution along the aircraft flight path at the expense of limited area coverage.
The aircraft observations made during the Antarctic and Arctic ozone campaigns proved invaluable in unraveling the respective roles of dynamics and chemistry in the formation of the ozone hole during the austral spring. The importance of high-resolution easurements is further suggested by the predictions of increasingly detailed three-dimensional models which show that trace gases are distributed with spatial structures on many scales and that these structures can form clear signatures of specific dynamical activity.