The planning and execution of ER‐2 and DC‐8 aircraft flights over Antarctica, August and September 1987

During August and September 1987, instrumented ER‐2 and DC‐8 aircraft flew 12 and 13 flights over Antarctica, respectively, to investigate the dramatic loss of ozone that has occurred there in the lower stratosphere during recent austral springs. The flights, which are documented in some detail, provided a wealth of data on homogeneous gas phase composition, upon polar stratospheric clouds, and upon tracers for dynamic motion. An important aspect of the ER‐2 data is that periods of high surface winds at Punta Arenas, Chile, which generally prevented a flight, frequently coincided with equatorward extension of the vortex toward the flight track region (53°–72° S, 60°–80° W). The ER‐2 flights are thus biased toward days when the vortex was being pushed away from the tip of South America and the Antarctic Peninsula. Any attempt to use the ER‐2 data as a time series must take into account the variable position of the vortex edge along the flight track. At DC‐8 flight levels, numerical weather prediction models had a tendency to underestimate the wind speeds by up to 50% in situations of strong meridional flow. Since such events had detectable effects on the lower stratospheric vortex, this too could be an important limitation.