Mid-latitude ozone depletion

Solomon, S. (1997) Mid-Latitude Ozone Depletion, in G.P. Brasseur (ed.), The Stratosphere and Its Role in the Climate System, NATO ASJ Series Series I Global Environmental Charge, Vol. 54, Springer-Verlag... 

Observations of enhanced Antarctic and mid-latitude ozone depletion following the eruption of Pinatubo confirm the impact of liquid aerosol surfaces on chlorine and nitrogen partitioning chemistry. Observations and laboratory studies have demonstrated the efficacy of heterogeneous... 

Observations show that about 25% of the observed mid-latitude ozone column depletion occurs above about 25 km, in the altitude range where gas-phase photochemistry is rapid and it is difficult for dynamics to compete (see e.g., SPARC, 1998). A further contribution due to PSC processing and to vortex breakdown is highly likely. Thus, a substantial chemical contribution of at least half of the trend in the column seems difficult to dispute even if locally-driven chemical ozone depletion in the mid-latitude lower stratosphere were to be substantially smaller than suggested by modelling studies and by the post-Pinatubo measurements described above. Thus, the evidence suggests that chlorine chemistry has played an important and very likely dominant role in the observed trends in mid-latitude ozone over the past two decades (for a recent review, see WMO/UNEP, 2003). 

Finally, the idea of the coupling between nucleophilic attack and proton transfer in the reaetions just discussed provides an interpretive framework for another important atmospheric reaction, namely the hydrolysis of dinitrogen pentoxide N2O5, thought to play an important role in mid-latitude global ozone depletion. 28,29 Indeed a related mechanism was suggested in ref 5 for the low acidify condition hydrolysis. 

Solomon, S R. W. Portmann, R. R. Garcia, W. Randel, F. Wu, R. Nagatani, J. Gleason, L. Thomason, L. R. Poole, and M. P. McCormick, Ozone Depletion at Mid-Latitudes Coupling of Volcanic Aerosols and Temperature Variability to Anthropogenic... 

The final objective of the study is to show a possible decrease in the ozone amount in the filaments as a function of time when ozone destruction takes place inside the vortex. Clearly, the number of events at the OIIP station is too small to detect such a behaviour. But the perspective is to use more ground based stations and more height levels in the potential vorticity advection model MIMOSA as well as to include the REPROBUS chemistry scheme in the advection model in order to understand the role of filaments in ozone depletion at mid-latitude. 

It is important to understand the sources and loss mechanisms of stratospheric sulfate aerosols. These aerosols are linked to the decrease in ozone at mid-latitudes because they hydrolyse N2O5, reducing the amount of NOx that would otherwise limit the efficiency of chlorine-catalysed ozone depletion. In addition these aerosols scatter light, cooling the planet [127]. Their concentration increases dramatically following major volcanic eruptions however they are always present at background levels. The source of these background aerosols is a matter of debate. In 1976 Paul Crutzen presented the idea that sulfate aerosols result from the photolysis of carbonyl sulphide [128] ... 

Anthropogenic emissions cause the depletion of the ozone. This is generally known through reports on the hole in the ozone layer. Although these reports referred only to the Antarctica area, ozone depletion is now also discernible to a lower degree on the mid-latitudes (e.g. Europe). 

The discovery of the Antarctic ozone hole naturally raised the question of whether mid-latitudes might also display greater ozone depletion than... 

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