Determination of stratospheric ozone at ground level using 7Be/ozone ratios

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Abstract
The 7Be and O3 concentrations were measured and the 7Be/O3 ratios calculated for air particulates collected on several flights of two specially equipped commercial B747 jetliners between altitudes of 10 and 12 km and latitudes of 21° to 55° N. Upper tropospheric 7Be concentrations averaged about 520 pCi/10³m³, whereas the stratospheric average was about 4,700 pCi/10³m³. The 7Be/O3 ratio at 35° ‐ 42° N was determined to be 10.78 pCi/10³m³/ppbv for April‐June 1978. Concentrations of 7Be and O3 were also measured daily during June and July 1977 at Whiteface Mountain, New York. Daily variations in 7Be data indicated the arrival of a stratospheric air mass on June 15‐16. Comparison of 7Be concentrations show approximately a tenfold dilution of the stratospheric air during tropospheric descent. The 7Be/O3 ratio on June 15‐16 was 9.8 pCi/10³m³/ppbv within experimental error of the stratospheric value. This suggests that at least at times, stratospheric air, although diluted, reaches ground level without significant relative fractionation of 7Be and O3. Assuming this to be true on days when 7Be concentration is > 200 pCi/10³m³ (or ≥ 5% of the stratospheric value), we have determined the stratospheric ozone concentration at Whiteface Mountain to vary between 19 and 47 ppbv for summer months. Thus at a remote location such as Whiteface Mountain both stratospheric and the tropospheric sources play an important role.

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