Sir - The two recent, and excellent, articles, "A340 findings indicate ozone is 'not being destroyed'" and "Emission control" (Flight International, 17-23 January, P20, and 31 January-6 February, P69), contain some misinterpretations on the MOZAIC (Measurement of Ozone by Airbus In-service Aircraft) programme.
Both mention ozone depletion, but, at subsonic cruise levels, it is ozone production, which may be a concern. (Above levels of 16km - supersonic-cruise level - or so, a different set of chemical reactions dominates.)
This ozone production (by nitrogen oxide in the engine exhaust) takes several weeks, during which the air becomes distributed around the globe. The A340 measurements cannot, therefore, provide immediate evidence for or against such production or its quantity.
The goal of the MOZAIC programme is to help understand the atmosphere and how it is changing, with emphasis on the effects of subsonic aircraft. It is doing this by providing a vast amount of data to develop and test computer models of the atmosphere, the only way in which we can assess the effect of current, or future, emissions (from aircraft, or other sources).
Incidentally, in the second article, the factor-of-five increase in ozone has occurred since 1870, not 1970.
Part funding by the European Commission and collaboration between Airbus, the airlines and several research institutes mentioned in the articles is providing data for European scientists to exploit.
Dr ALAIN MARENCO
Co-Ordinator of MOZAIC Programme
Dr CHRIS HUME
British Aerospace
Editors of MOZAIC News
Toulouse, France
Source: Flight International
