Balloon‐borne measurements of middle atmosphere aerosols and trace gases in Antarctica

Abstract

Although trace stratospheric gases such as ozone have been measured in Antarctica from the surface since 1957 and from balloons since 1966 and stratospheric aerosols have been measured routinely by balloon‐borne particle counters since 1972, only recently has any real interest in these measurements developed. This new awareness is directly related to the realization, in 1985, that springtime Antarctic total ozone had declined about 50% since about 1977. Such an unprecedented, unpredicted change understandably created a great deal of interest in past Antarctic ozone‐related measurements. Early theories of this phenomenon included both chemical and dynamical ozone depletion mechanisms. Chemical theories generally utilized stratospheric particles (created in the low‐temperature environment of the Antarctic stratosphere) to enhance chemical conversion of reservoir chlorine compounds to active ozone‐destroying chlorine heterogeneously. Dynamic models utilized particle heating to lift the polar vortex air mass in spring and cause reductions in ozone. Thus these theories generated an interest not only in ozone measurements but also in stratospheric particulates (aerosols) and in measurements of trace gases which could be used as tracers of atmospheric motions, for example, nitrous oxide. In 1986 the first major field studies, in the National Ozone Expedition, were directed at this problem. In the following review of in situ balloon‐borne measurements of aerosols and trace gases the limited amounts of data prior to 1986 are summarized. The new measurements of 1986 have revealed much concerning the nature of the ozone depletion mechanism. While the steady decline in ozone in the 12‐ to 20‐km region in September can probably only be explained by fast chemistry, the phenomenon appears to be shaped spatially and temporally by dynamical phenomena. The next several years will see expanded research in this area, not only in Antarctica but also in other regions in an attempt to detect reductions in ozone which may occur at these locations.