Abstract. Calculations of equivalent length from an artificial advected tracer provide new insight into the isentropic transport processes occurring within the Antarctic stratospheric vortex. These calculations show two distinct regions of approximately equal area: a strongly mixed vortex core and a broad ring of we. akly mixed air extending out to the vortex boundary. This broad ring of vortex air remains isolated from the core between late winter and midspring. Satellite measurements of stratospheric H20 confirm that the isolation lasts until at least mid-October. A three-dimensional chemical transport model simulation of the Antarctic ozone hole quantifies the ozone loss within this ring and demonstrates its isolation. In contrast to the vortex core, ozone loss in the weakly mixed broad ring is not complete. The reasons are twofold. First, warmer temperatures in the broad ring prevent continuous polar stratospheric cloud (PSC) formation and the associated chemical processing (i.e., the conversion of unreactive chlorine into reactive forms). Second, the isolation prevents ozone-rich air from the broad ring mixing with chemically processed air from the vortex core. If the stratosphere continues to cool, this will lead to increased PSC formation and more complete chemical processing in the broad ring. Despite the expected decline in halocarbons, sensitivity studies suggest that this mechanism will lead to enhanced ozone loss in the weakly mixed region, delaying the future recovery of the ozone hole.

Abstract.Observations indicates it is not isentropically mixed. A strong local maximum in mixing ratio at the centre of the Antarctic vortex in the mid-stratosphere indicates it is not well mixed in the mid-stratosphere also. There is little evidence of significant structure inside the Arctic vortex.

In Scotland all 13 universities and a number (8) of other related institutions of higher education are connected on a high bandwidth computer network. Organizationally, this is composed of four interconnected Metropolitan Area Networks (MANs). The high bandwidth (155 Mbit/s) and the network's operation under ATM (Asynchronous Transfer Mode) enables routine use of high quality video-conferencing between institutions. Each institution has at least one (all the universities have two) video-conferencing suites, fully equipped with audio and video equipment and direct network access for PCs

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Video-conferencing was used to share a short series of lectures between several universities. A high bandwidth network (155Mbit/s) permitted near broadcast TV quality video to be combined with fully mixed, high-quality audio. The lectures were supported by visual aids made available using Microsoft NetMeeting to provide multipoint, shared applications. NetMeeting is shown to be a stable and effective platform for distributing multimedia material at a much higher resolution than is possible using the video signals common in most video-conference lectures, although care must be taken when constructing animated material.