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Lodovica Illari

Abstract

Dynamical features of the warm blocking anticyclone which persisted over Europe during the summer of 1976 are studied using National Meteorological Centre analyses. The dynamics am presented from the perspective of quasi-geostrophic potential vorticity q. The block is shown to be a region of anomalously low, almost uniform q¯. Computed balances in the 300 mb monthly mean quasi-geostrophic potential vorticity equation show that the mean flow advection v¯˙∇q¯ and the eddy forciv′˙∇q′ of q¯ are of comparable magnitude and have the tendency to balance one another. It is suggested that transfer by synoptic scale systems acts to maintain the q¯ anomaly against its advection downstream.

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Lodovica Illari and John C. Marshall

Abstract

Using twice daily synoptic charts, objectively analyzed at the National Meteorological Centre, horizontal eddy fluxes of temperature and quasi-geostrophic potential vorticity are computed for the month Of July 1976, when a blocking anticyclone was centered over western Europe. The local time-averaged eddy variance equations are used to provide a dynamical basis for interpreting the spatial pattern of eddy fluxes, and their relation to mean gradients. It is shown that a rotational non-divergent flux can be identified, the cross-gradient component of which balances the mean flow advection of eddy variance. The remaining flux is the dynamically significant one which helps maintain the block and can be understood in terms of a response to sources and sinks of eddy variance.

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Lodovica Illari, John Marshall, and W. D. McKenna

Abstract

The “Weather in a Tank” project offers instructors a repertoire of rotating tank experiments and a curriculum in fluid dynamics to better assist students in learning how to move between phenomena in the real world and basic principles of rotating fluid dynamics that play a central role in determining the climate of the planet. Despite the increasing use of laboratory experiments in teaching meteorology, many teachers and students do not have access to suitable apparatuses and so cannot benefit from them. This article describes a “virtually enhanced” laboratory that could be very effective in getting across a flavor of the experiments and bring them to a wider audience. In the pedagogical spirit of Weather in a Tank, the focus is on how simple underlying principles, illustrated through laboratory experiments, shape the observed structure of the large-scale atmospheric circulation.

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