Ozone Observations

The last decade has seen a consolidation of earlier results, both experimental and theoretical, with much attention being paid to details. Stratospheric chemistry has developed into an extremely complex subject, as about 100 individual chemical reactions are now known to be involved. Of these, only the most important ones can be discussed in this chapter. 

Measurements of stratospheric ozone fall into two classes total ozone observed from the ground or by means of satellites, and vertical distributions derived from balloon or rocket sondes. The data are too numerous for individual discussion only the most obvious features can be treated. The subject has been reviewed by Craig (1950), Paetzold and Regener (1957), Vassy (1965), and by Diitsch (1971, 1980). These reports trace the progress achieved in our understanding of the behavior of stratospheric ozone. 

Ground-based measurements of total ozone use the Dobson spectrometer. This instrument measures the column density of ozone in the atmosphere by optical absorption, with the sun or the moon as background source. The data are expressed as an equivalent column height at standard pressure and 

In the tropics the situation is somewhat different. Here, the mean motion is directed upward as it follows the ascending branch of the Hadley cell, thus counteracting the downward flux of ozone by eddy diffusion. The ozone concentration rises more gradually, and the gradient at the tropopause is essentially negligible. Since in addition the tropopause level is fairly stable, there is practically no influx of ozone into the troposphere. Instead, ozone undergoes lateral, poleward transport and can then enter the troposphere at midlatitudes, in part via the subtropical tropopause breaks 

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The continued depletion of Antarctic ozone and the appearance of spring ozone depletion over the Northern hemisphere between the latitudes of 40 and 55 N. detectable by the improved analysis of older data and the development of better ozone observational methods, resulted in a tightening of the CFC phaseout provisions during the 1990 and 1992 reviews,10 held in London and Copenhagen, respectively, and the extension of the restrictions to other, potentially ozone-depleting substances. Table 2 summarizes the current position. 

There is strong observational evidence that tropospheric ozone can be destroyed by reactions in addition to those discussed so far. Surface ozone observations during polar sunrise in the Arctic have frequently shown the occurrence of unmeasurably low ozone concentrations, coinciding with high filterable Br" (31). Further measurements (32) identified BrO as one of the active Br compounds, which, as is well known from stratospheric measurements, may rapidly attack ozone by series of catalytic reactions, such as... 

In this study we will present aspects of STE in relation with the budget and concentrations of ozone in the troposphere, specifically in the Northern Hemisphere. Firstly, we present ozone observations in the tropopause region from the measurement campaign MOZAIC, and discuss their correlation with potential vorticity. The results have been used to improve the parameterization of stratospheric ozone in a coupled tropospheric chemistry - general circulation model. We will show examples of the performance of the model regarding the simulation of ozone in the tropopause region, and present the simulated seasonality of cross-tropopause ozone transport in relation to other tropospheric ozone sources and sinks. Finally, we will examine and compare the influence of cross-tropopause transports to surface ozone concentrations for simulations with contemporary, pre-industrial, and future emission scenarios. 

Examination of ozone observations from MOZAIC and potential vorticity... 

We have addressed several aspects of STE of ozone and the impact on tropospheric ozone levels. Using ozone observations in the upper troposphere and lower stratosphere from MOZAIC, we have examined the rdation between ozone and PV in the lower stratosphere. A distinct seasonality in the ratio between ozone and PV is evident, with a maximum in spring and minimum in fall associated with the seasonality of downward transport in the meridional circulation and of the ozone concentrations in the lower stratosphere. The ozone-PV ratio is applied in our tropospheric chemistry-climate model to improve the boundary conditions for ozone above the tropopause, to improve the representativity of simulated ozone distributions near synoptic disturbances and realistically simulate cross-tropopause ozone transports. It is expected that the results will further improve when the model is applied in a finer horizontal and vertical resolution. 

A more detailed overview of the main components of the GEOS-DAS system the forecast model, the input data (total ozone observations from Total Ozone Mapping Spectrometer /TOMS/ and vertical ozone profiles from the Solar Backscatter Ultra Violet instrument /SBUV/, the analysis scheme and its implementation could be easy found in the paper of Riishojgard [19]. 

Total ozone observations have been collected since 1992 by means of Brewer spectrophotometry at Rome (41.9°N, 12.5°E, 60 m a.s.l.) and lspra (45.8°N, 8.63°E, 240 m a.s.l.). A filtering technique is applied to the Dobson ozone long time series of Vigna di Valle (42.08°N, 12.22°E, 262 m a.s.l.), Arosa (46.78°N, 9.68°E, 1840 m a.s.l.) and Lerwick (60.13°N, 1.18°W, 80 m a.s.l.) and to the Italian Brewer ozone data, in order to investigate on different time scales [1]. The aim of this analysis is to single out any effective ozone trend, together with the role of ozone fluctuations due to weather patterns, at the selected Northern Hemisphere middle latitudes sites. 

Figure I. Ispra total ozone observations from January 1 1992 to April 30 1998...

Fig. 1 Continental source attribution of the ozone observed on each day of 2008 at the EMEP rural monitoring station GB0049R at Weyboume on the North Norfolk coast of eastern England using ozone labelling techniques in a global and a regional photochemical model. Key regional refers to the ozone advected directly over the local- and regional-scales to the location North America to that formed over that continent and over the North Atlantic and east Pacific Asia to that formed over that continent and over the western Pacific Europe-interc to that advected intercontinentally around latitude circles and back into Europe Tropical to that from the southern hemisphere and tropics...

When the mass-independent isotopic fractionation chemical process was first discovered by Thiemens and Heidenreich (1983), there existed no physical-chemical mechanism that accounted for the ozone observations. In this paper, a mechanism based upon optical self-shielding was proposed. Although this mechanism may not account for the experimental results, there are potential cosmochemical environments where self-shielding may be operative, as discussed in this paper. These potential applications will be discussed in detail in a later section of this chapter. 

The relatively intense heating which takes place near 25 km. in the summer is an unanticipated feature of these results. But with hindsight it is easily understood. First consider the distribution of ozone observed during the summer (Figure 2). There was very little ozone at low levels, and a very sharp maximum concentration of ozone just below 30 km. Thus, the thermal emissions from the earth, at a time when the surface of the earth is warmest, could pass almost unabsorbed through the lowest 20... 

Rocket experiments by personnel of the Naval Research Laboratory 22-24) have extended ozone observations to altitudes up to 70 km. In this work V-2 or Aerobee... 

Ozone observations near 90 km available from the Solar Mesosphere Explorer are characterized by strong latitudinal gradients and large local variations. Barth et al. (1983) suggested that this may result from downward transport of oxygen from the thermosphere because of the long Ox lifetime at these altitudes, as shown in Figure 5.3. 

Chubachi, S., A special ozone observation at Syowa station Antarctica from February 1982 to January 1983, in Atmospheric Ozone. S. Zerefos and A. Ghazi (eds.), Reidel, Dordrecht, pp. 285, 1985. 

Section 5.6.3 discussed the chemistries of the halogens chlorine and bromine, and outlined their interactions with one another and with ozone. More than two decades after the pioneering prediction of possible ozone destruction through humankind s use of halogenated chemicals, upper stratospheric ozone observations began to reveal systematic depletion indicative of a changing chemical state (see SPARC, 1998, and references therein). 

Figure 6.10. Observations of the vertical profile of ozone observed at the South Pole in the Octobers of the late 1960s and early 1970s, contrasted with those of 1986 and 1997. Total ozone (DU) is indicated for each profile, from Hofmann et al. (1997). The right hand panel shows a typical polar stratospheric cloud observed at the South Pole from the observations of Collins et al. (1993). From Solomon (1999).

Figure 6.23. The top panel shows the total tropospheric chlorine content estimated from the baseline scenario in WMO/UNEP (1998) this is based on a gas-by-gas analysis like those shown in Figure 6.22. The bottom panel shows the changes in the 5-year running mean ozone observed over Switzerland (Staehelin et al., 1998a,b) compared to a model calculation for 45°N applying the same time averaging, with and without considering the effects of volcanic enhancements in aerosol chemistry (from the model of Solomon et al., 1996 1998). The major eruptions since 1980 were those of El Chichon in 1982 and Mt. Pinatubo in 1991. Updated from Solomon (1999).

Chubachi, S., Preliminary result of ozone observations at Syowa Station from February, 1982, to January, 1983. Mem Natl Inst Polar Res Jap, Spec Issue 34, 13, 1984. 

Heterogeneous chemistry occurring on polar stratospheric cloud particles of ice and nitric acid trihydrate has been established as a dominant factor in the aggravated seasonal depletion of ozone observed to occur over Antarctica. Preliminary attempts have been made to parameterize this chemistry and incorporate it in models to study ozone depletion over the poles (91) as well as the potential role of sulfate particles throughout the stratosphere (92). 

Instead of a time constant for the approach to steady state one may also consider the time required to replenish the average amount of ozone observed at a given altitude by the photodissociation of oxygen. This... 

Fabian and Pruchniewicz (1976, 1977) 425 275 From the phase shift of maxima between total and surface ozone observed at 27 stations... 

Galbally, I. E. (1971). Surface ozone observations at Aspendale, Victoria 1964-70. Atmos. Environ. 5, 15-25. 

Wexler, H., W. Moreland, and W. Weyant (1960). A preliminary report on ozone observations in Little America, Antarctica. Mon. Weather Rev. 88, 43-45. 

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