Topics in Rotating and Stratified Fluids
Résumé
The Earth’s oceans and atmosphere are affected by background rotation and densitystratification implying, respectively, buoyancy and Coriolis forces. These forces are keyingredients of most Geophysical and many Astrophysical flows. Under the influence ofthese body forces, the vertical kinetic energy of turbulent motions is converted into potentialenergy via mixing and the emission of wave motions, so that the motion eventually becomeshorizontal. By the inverse energy cascade, two-dimensional flows are known to organiseinto large coherent vortex structures, which for example, can be observed in satellite imagesof the Earth’s atmosphere and oceans; the observed patterns can be interpreted as high andlow pressure regions in the case of the atmosphere and as meso-scale eddies located nearthe surface in the oceans.Significantly different flow features come into play at different time scales of the mo-tion. At large times, the flow fields organise into quasi-two-dimensional patterns that containcoherent vortices, while on short timescales, small-scale turbulence is induced by local forc-ing or wave-breaking. On yet different time scales, wave mean-flow interactions take place.These different flow features coexist and interact thus making each of them individuallyrelevant, while rendering the full dynamics of geophysical flows extremely interesting andcomplicated.During the past decades, an increasing number of scientists have devoted their intereststo model large and meso-scale ocean and atmospheric flows. Only recently, ocean andatmosphere models have improved to such an extent that they are capable of running with lessartificial diffusion and instead require better parameterisations of different fundamental flowfeatures. Equally, recent experimental techniques allow for higher resolution measurements.This issue contains a selection of papers, that present the state-of-the-art of fundamentalaspects of geophysical flows such as diapycnal mixing in isotropic and anisotropic turbulentflows, wave-mean flow interaction and wave breaking, the dynamics of coherent vortexinteraction and the statistical properties of bounded two-dimensional flows.These papers were presented at the mini-symposium on “rotating and stratified fluids”of the XXIII general assembly of the International Union of Geodesy and Geophysics(IUGG) held in the summer of 2003 in Sapporo in Japan. The IUGG is a world-widenon-governmental, scientific organisation, established in 1919, and is dedicated to the international promotion and coordination of scientific studies of Earth (physical, chemical,and mathematical) and its environment in space of which general assemblies are organisedat four-year intervals.This mini-symposium was organised by the co-conveners George Carnavale (Universityof California, San Diego, USA), Evgueni Ermanyuk (Russia), Harindra Fernando (ArizonaState University, USA), Rudolf Kloosterziel (School of Ocean & Earth Science and Tech-nollogy, Hawaii, USA), Oscar Velasco Fuentes (Cicese, Mexico), James Riley (Universityof Washington, USA), and Marius Ungarish (Technion, Isreal) and convener, Jan-Bert Flor(Laboratoire des Ecoulements Geophysiques et Industriels, France). All of the articles inthis volume have received intensive external reviews similar to, and in keeping with, thegeneral policies established by the Editor of “Dynamics of Atmospheres and Oceans".