Time-averaged LDA measurements and time-resolved numerical flow predictions were performed to investigate the laminar flow induced by the harmonic in-line oscillation of a circular cylinder in water at rest. The key parameters, Reynolds number Re and Keulegan–Carpenter number KC, were varied to study three parameter combinations in detail. Good agreement was observed for Re=100 and KC=5 between measurements and predictions comparing phase-averaged velocity vectors. For Re=200 and KC=10 weakly stable and non-periodic flow patterns occurred, which made repeatable time-averaged measurements impossible. Nevertheless, the experimentally visualized vortex dynamics was reproduced by the two-dimensional computations. For the third combination, Re=210 and KC=6, which refers to a totally different flow regime, the computations again resulted in the correct fluid behaviour. Applying the widely used model of Morison et al. (1950) to the computed in-line force history, the drag and the added-mass coefficients were calculated and compared for different grid levels and time steps. Using these to reproduce the force functions revealed deviations from those originally computed as already noted in previous studies. They were found to be much higher than the deviations for the coarsest computational grid or the largest time step. The comparison of several in-line force coefficients with results obtained experimentally by Kühtz (1996) for β=35 confirmed that force predictions could also be reliably obtained by the computations.

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The world wide distribution of total ozone and its changes with season are discussed as well as the variability on different time scales. A climatology of the vertical ozone distribution is presented and an attempt is made to derive some inference on ozone transport by the general circulation and its interaction with photochemical processes. It is found that longer observational series in an improved network are needed for puttting such a derivation on a firmer basis. The observed year-to-year changes of world wide total ozone and of the vertical distribution indicate the importance of the quasi-biennial variation of the circulation in the tropical stratosphere for the poleward ozone flux. The suggested variation of ozone concentration in the upper stratosphere with the sunspot cycle must be further substantiated.On traite de la distribution dans le monde entier de l'ozone total, de ses variations avec les saisons et de ses variations selon diffCrentes Cchelles de temps.On prCsente une climatologie de la distribution verticale d'ozone et l'on tente d'en tirer les cons6quences sur le transport d'ozone, la circulation gCnCrale et I'interaction avec des processus photochimiques. On en conclut qu'un nombre plus ClevC d'observations dans un rCseau amtliori serait nkcessaire afin d'Ctablir sur une base plus solide de telles relations.Les changements de la quantitC totale d'ozone observCs d'annCe en annCe dans le monde entier et de la distribution verticale montrent l'importance de la variation quasibiennale de la circulation dans la stratosphere tropicale pour le transport d'ozone vers les p6les. Introduction Total AmountThe emphasis in ozone research has, during the Observational Techniques past few years, shifted towards the theoretical The standard instrument for total ozone side in connection with the rapid new develop-observations is the Dobson spectrophotometer ments in photochemistry and also because of the with almost 100.units distributed over the world. prospects introduced by this of a possible Although the actual observation with this anthropogenic influence on the ozone layer. instrument is simple and rapid, good calibration Observational efforts have shifted towards and maintenance are rather difficult wherebv the measurements of other trace constituents which play a role in the new integrated photochemical system and which had hitherto not been directly observed at all at stratospheric levels. Although we already have a fairly broad knowledge of the ozone distribution in the atmosphere (which shall be reviewed in this paper) further and improved observations of the central substance of the new integrated photochemical system, namely the ozone, are still urgently needed. The intimate interaction between photochemical and transport processes demands comparison between a rather detailed observational material and the model studies.

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The performance characteristics of the electrochemical and chemiluminescent ozonesondes were investigated through analysis of comparative ascents. A direct intercomparison of short duration was made at Boulder, Colorado, in October 1964. Further comparison was obtained by analysis of ascents made on the same day on many individual days using the electrochemical instrument at Boulder, Colorado, and the chemiluminescent instrument at Fort Collins, Colorado. Good agreement was found between the two methods of ozone measurement. Observed differences in the comparative profiles obtained in the October test series were generally within a few nanobars partial pressure. Similar results were obtained from the Boulder‐Fort Collins data comparison. However, this analysis confirmed the fact that a correction is required for a systematic loss of sensitivity with time in the chemiluminescent‐type sonde ascents in the winter and spring of 1963–1964.