Abstract. Simultaneous in situ measurements of the long-lived trace species N20, CH4, CFC-12, CFC-113, CFC-11, CC14, CH3CC13, H-1211, and SF6 were made in the lower stratosphere and upper troposphere on board the NASA ER-2 high-altitude aircraft during the 1994 campaign Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft. The observed extratropical tracer abundances exhibit compact mutual correlations that show little interhemispheric difference or seasonal variability except at higher altitudes in southern hemisphere spring. The environmental impact of the measured source gases depends, among other factors, on the rate at which they release ozone-depleting chemicals in the stratosphere, that is, on their stratospheric lifetimes. We calculate the mean age of the air from the SF 6 measurements and show how stratospheric lifetimes of the other species may be derived semiempirically from their observed gradients with respect to mean age at the extratropical tropopause. We also derive independent stratospheric lifetimes using the CFC-11 lifetime and the slopes of the tracer' s correlations with CFC-11. In both cases, we correct for the influence of tropospheric growth on stratospheric tracer gradients using the observed mean age of the air, time series of observed tropospheric abundances, and model-derived estimates of the width of the stratospheric age spectrum. Lifetime results from the two methods are consistent with each other. Our best estimates for stratospheric lifetimes are 122 + 24 years for N2 ¸, 93 + 18 years for CH4, 87 + 17 years for CFC-12, 100 + 32 years for CFC-113, 32 + 6 years for CC14, 34 + 7 years for CH3CC13, and 24 + 6 years for H-1211. Most of these estimates are significantly smaller than currently recommended lifetimes, which are based largely on photochemical model calculations. Because the derived stratospheric lifetimes are identical to atmospheric lifetimes for most of the species considered, the shorter lifetimes would imply a faster recovery of the ozone layer following the phaseout of industrial halocarbons than currently predicted.

to the Gleissberg minimum early in this century. However, the observed increase of about 20% is four times that expected based on the sunspot numbers.The observed high 44Ti and the inferred high GCR flux during the Gleissberg minimum suggest a much-weakened modulation of GCR during prolonged solar quiet periods. The heliosphere, during the 11vear solar cvcles. is divided into two hemispheres of dpposite polarity by a wavy heliospheric neutral sheet (HNS) whose inclination to the sun's rotational eauator increases from a few degrees at solar minimum to >70° at solar maximum and whose undulations also increase with solar activity (15). The HMF is relatively smooth during the solar minima. The enhanced GCR fluxes required for the higher production of 44Ti can be achieved if (i) the HNS becomes smooth and remains close to the helioequator; (ii) the HMF becomes weak, more regular, and orderlv; or (iii) the size of the , , . ,

Simultaneous in situ measurements of the concentrations of OH, HO(2), ClO, BrO, NO, and NO(2) demonstrate the predominance of odd-hydrogen and halogen free-radical catalysis in determining the rate of removal of ozone in the lower stratosphere during May 1993. A single catalytic cycle, in which the rate-limiting step is the reaction of HO(2) with ozone, accounted for nearly one-half of the total O(3) removal in this region of the atmosphere. Halogen-radical chemistry was responsible for approximately one-third of the photochemical removal of O(3); reactions involving BrO account for one-half of this loss. Catalytic destruction by NO(2), which for two decades was considered to be the predominant loss process, accounted for less than 20 percent of the O(3) removal. The measurements demonstrate quantitatively the coupling that exists between the radical families. The concentrations of HO(2) and ClO are inversely correlated with those of NO and NO(2). The direct determination of the relative importance of the catalytic loss processes, combined with a demonstration of the reactions linking the hydrogen, halogen, and nitrogen radical concentrations, shows that in the air sampled the rate of O(3) removal was inversely correlated with total NOx, loading.