Surface Ozone Observations Research Articles

Atmospheric ozone at South Pole, Antarctica, in 1986

Vertical‐profile ozone distributions and variations, as well as the annual course of total ozone, are described for South Pole, Antarctica, from observations made throughout 1986 with electrochemical concentration cell (ECC) ozonesondes and a Dobson spectrophotometer. Ozone decrease in the stratosphere in September and October months was the highlight of the measurements. From mid‐August to October 7, total ozone decreased by about 40%, with the bulk of the decrease occurring between 12 and 21 km. Within this region the maximum rate of ozone decrease, with an exponential decay half‐life of 11 days, was observed between September 20 and October 15, when column ozone and ozone volume mixing ratio at 16±1 km decreased by 78% and column ozone between 12 and 21 km decreased by 50%. This time interval was characterized by virtual cessation of ozone flux into the stratosphere above South Pole that might have resulted either from movement of the polar vortex or from ozone advection from lower latitudes. In contrast, ECC ozonesonde data obtained in 1971 show ozone to have arrived at South Pole above 30 mbar in mid‐September and above 100 mbar in late September, 6 and 3 weeks, respectively, earlier than it did in 1986. Supporting evidence for a temporal change in the timing of ozone transport to Antarctica by atmospheric circulation comes from 1974–1986 surface ozone observations at South Pole, which show a negative surface ozone growth rate during summer months, a positive growth rate during winter months, and an increase in the amplitude of the annual cycle by a factor of 2. A correspondence is shown between El Niño‐related highs in sea surface temperature anomalies in the equatorial Pacific Ocean and lows in October–December total ozone averages that were observed at South Pole in the 1960s and 1970s. Such ozone lows occurred during years of increased circumpolar vortex stability, late stratospheric warming, and late ozone arrival in Antarctica. It is suggested that the 1982–1983 El Niño, which was of unprecedented intensity, similarly affected the transport of ozone to Antarctica, thereby contributing to the observed springtime ozone decrease. The transport of air parcels from 50°–60°S latitude into the tropopause and low stratosphere region of Antarctica, as suggested by 10‐day, isobaric back trajectory analyses, may also contribute to the Antarctica springtime ozone decrease and warrants further investigation.

Surface ozone distributions and variations from 1973–1984: Measurements at the NOAA Geophysical Monitoring for Climatic Change Baseline Observatories

Surface ozone data are presented from up to 12 years of continuous measurements at Point Barrow, Alaska; Mauna Loa, Hawaii; American Samoa, South Pacific; and South Pole, Antarctica. Annual cycle characteristics of the data are described relative to atmospheric mixing and transport processes that give rise to the observed annual ozone distributions. Both positive and negative long‐term trends are exhibited by the data. From examination of trends in the seasonal and monthly data, it is concluded that the cause of the trends is most likely a fluctuation over the years in the stratospheric‐tropospheric exchange and tropospheric circulation processes that distribute ozone within the troposphere, coupled with tropospheric circulation disturbances such as those associated with the El Niño/Southern Oscillation events of 1976 and 1982–1983. Because the positive ozone trend at Barrow occurs during summer months, photochemical ozone production in increasingly polluted Arctic air cannot be ruled out. Ozonesonde data are used to show that the surface ozone observations at Mauna Loa observatory in the downslope wind regimes, and at South Pole, are representative of ozone measurements in the free troposphere, and that the ozone trends observed at Point Barrow and Samoa are likely representative of the lower free troposphere even though the measurements are made in air modified within the boundary layer.

Surface Ozone and Peroxyacetyl Nitrate (PAN) Observations at Rural Locations in Alberta, Canada

In order to better understand and control photochemical air pollution generated under the cold, dry climatic conditions of Alberta, an extensive program of environmental research studies was initiated in 1975. One objective was to measure concentrations of surface ozone, peroxyacetyl nitrate (PAN), and other pollutants associated with urban and industrial developments and to predict future trends in photochemical air pollution. To enable predictions to be made it was necessary to delineate the contribution of background levels of ozone and PAN to the urban centers and to measure background concentrations in the presently remote northern areas of the province. Measurements were made at three remote locations: the Kananaskis Valley, Birch Mountain, and Bitumount, and at two nonurban locations, Kavanagh, and Bon Accord. Mean ozone concentration in remote locations in Alberta (50/sup 0/ N to 58/sup 0/ N) during spring and early summer months fell in the range of 11-46 ppB. Daily maxima in Pan concentrations, measured at a remote location in the Rocky Mountains, were generally less than 1 ppB. Elevated PAN concentrations of 2.2 and 2.3 ppB were measured on two days when smoke from forest fires, burning 350 km to the north, entered the area. This suggests a majormore » natural source for PAN together with medium range transport. 2 figures, 2 tables. (DP)« less

Surface Ozone Observations in Rural and Remote Areas

Surface Ozone Observations in Rural and Remote Areas

Surface ozone observations at Aspendale, Victoria, 1964–1970

Five years of observations of the ozone concentration in the surface air at Aspendale, Victoria, are presented. On some occasions the concentrations of ozone (or oxidant) reach 0.1 ppm v v . Such high ozone concentrations are associated with high air temperatures and reduced intensity of ultra-violet radiation observed at the earth's surface. On such occasions it appears that there is local production of ozone near the earth's surface.