Tropospheric ozone annual variation and possible troposphere-stratosphere coupling in the Arctic and Antarctic as derived from ozone soundings at Resolute and Amundsen-Scott stations
The tropospheric ozone annual variation in the northern and southern polar regions is analyzed from ozone sounding data obtained at Resolute (74.41°N, 94.59°W) during a 15-year period (1974–1988) and Amundsen-Scott (South Pole) during a 7-year period (1967–1971, 1986–1987). Tropospheric ozone is always less abundant in the southern than in the northern polar region. The difference is greatest in spring in the tropopause layer where the Arctic ozone mixing ratio can be 5 × as large as the mixing ratio in Antarctica. The phase of ozone annual variation above Resolute changes (increases) gradually from the stratosphere across the tropopause to the middle troposphere. Unlike this, the phase of the Antarctic ozone annual harmonic has a discontinuity in the layer of the changing tropopause level, so that the annual harmonic in the upper troposphere, lower stratosphere is 4-to-5 months out of phase (earlier) to that above and beneath. Above both the Arctic and Antarctic stations, the ozone mixing ratio and its vertical gradient evolve in a similar manner in the wide layer from the lower stratosphere to the middle troposphere. This likely points out that ozone in this layer is controlled from above. An indication of the stratospheric-tropospheric ozone exchange above Resolute is noted from mid-winter to spring. The analysis of columnar tropospheric ozone changes gives an lower estimate of the cross-tropopause ozone flux up to 5. 1010 mol cm-2 s-1. Above the South Pole, the cross-tropopause ozone flux is not usually large. However, in winter, when the tropopause is not strongly pronounced, it can rise to 4.5. 1010 mol cm-2 s-1, but does not penetrate into the middle troposphere. There is also some evidence that early in the spring, when the stratospheric ozone “hole” is developed, the stratospheric-tropospheric exchange conducts the influence of the “hole” into the upper troposphere, where the integrated ozone destruction is estimated to be 8. 1010 mol cm-2 s-1. Correlation analysis gives no ozone-tropopause correlation in the Antarctic in winter, while in other seasons as well as during all seasons in the Arctic, there are negative correlation peaks just above the tropopause. DOI: 10.1034/j.1600-0889.1993.t01-1-00001.x