Observations of the stratospheric conductivity and its variation at three latitudes

Measurements of the atmospheric conductivity from nine high‐altitude balloon flights are presented. The measurements were obtained between the altitudes of 10 and 30 km at three locations widely separated in latitude, providing the opportunity to investigate conductivity variations on local and global scales. The data contribute to the set of global conductivity measurements, which are generally lacking. The conductivity profiles exhibit a considerable variability from day to day which does not correlate with solar or cosmic ray activity. The variations are apparently dominated by local effects. The conductivity measurements provide evidence of stratospheric aerosol layers with number densities of the order of 1000 cm−3. The observed variation of the conductivity with latitude is much larger than that predicted by a latitudinal variation of cosmic ray ionization alone. A global background distribution of aerosols is estimated and parameterized. By including the effects of aerosols and latitudinal temperature variations, the agreement between the predicted variation of conductivity with latitude and the observed variation is significantly improved. The implication is that present global models of the conductivity, which employ latitudinal variations based on cosmic ray ionization alone, may be improved by including the effects of latitudinal variations of temperature and aerosols. The effects of photoelectric emissions on relaxation time conductivity measurements are discussed.