Quasi-geostrophic stratified flow over isolated finite amplitude topography

The quasi-geostrophic response of a stratified stream incident upon isolated finite amplitude topography on a f-plane is examined in the limit of a Boussinesq, incompressible, inviscid fluid. Compact solutions are derived subject to the following stipulations: uniform upstream velocity and stratification, a circular obstacle and an entirely isentropic/isopycnic lower surface.It is shown that for a semi-infinite flow domain the criterion for Taylor cap formation (i.e., a region of closed streamlines) is . However, for the isentropic lower boundary condition the solutions exist (i.e., have physical validity) only if R₀F⁻¹ < 0.5. (Here R₀ and F refer to the Rossby and Froude numbers defined respectively in terms of the mountain half-width and height.) Also considered are the modifications both to the flow response and to the foregoing existence criterion that are induced by the introduction of an upstream profile comprising two layers of uniform but different stratification. In addition, the relationship of the derived solutions to the results obtained in previous studies is explored, and in particular an outline is given of the impact of adopting the ‘traditional’ simplified lower boundary condition.     

The environmental influence of a volcanic plume,a new technique of study,Mount Etna,sicily

Detailed study of the chemistry of volcanic plumes has previously been hindered by the difficulties of sampling, particularly if data on trace elements are required. In an attempt to overcome this problem, and to learn more about the regional effects of the plume of Mt. Etna, it was decided to investigate whether lichens, which are used as indicators of aerial pollution, would be suitable for this type of study. Samples collected from the slopes of Etna were assayed, mainly for heavy metals. The results show that this technique has great potential, that lichens can be used to determine semiquantitatively the minor and trace element composition of the plume, and can detect the influence of the plume on the chemistry of local rainfall.     

An orographically split mixed-layer and the alpine low-level jet

Summary A study is undertaken of the semi-geostrophic flow of shallow water incident tangentially upon a sharp leading edged, slender, orographic feature. The nature of the response is shown to depend upon the Froude number of the upstream flow and upon the orographic shape. In particular it is deduced that the orographically split flow has a laterally asymmetric response, and that for sub-critical upstream settings a jet can develop on one particular side of the orography. Features of an easterly low-level jet observed on the Alpine northside during the ALPEX project are compared with the theory.With 5 FiguresJosef Horn died in an Alpine accident in September 1987.     

Landslide Tsunamis: Recent Findings and Research Directions

— Underwater landslides can trigger local tsunamis with high runup, endangering human life and devastating coastal cities, offshore structures, communication cables, and port facilities. Unfortunately, hazards from underwater landslides are not well understood and the extents of their potential damage remain difficult to ascertain at present. There is immediate need for multidisciplinary research to improve our understanding and plan countermeasures for mitigating their hazards. Conceived in the wake of the Papua New Guinea earthquake landslide and tsunami of 1998, this volume summarizes the state-of-the-art knowledge on underwater landslides and their potential to generate tsunamis from the multidisciplinary perspectives of observational and engineering seismology, geotechnical engineering, marine geology, and hydrodynamics. These various fields of engineering and science offer new synergetic opportunities to examine landslide tsunamis. This paper makes recommendations on future research directions, and will hopefully advance scientists' and engineers' understanding of these natural hazards and assist planners in mitigating their risks.     

The stratigraphic and structural evolution of the Dzereg Basin, western Mongolia: clastic sedimentation, transpressional faulting and basin destruction in an intraplate, intracontinental setting

The Dzereg Basin is an actively evolving intracontinental basin in the Altai region of western Mongolia. The basin is sandwiched between two transpressional ranges, which occur at the termination zones of two regional‐scale dextral strike‐slip fault systems. The basin contains distinct Upper Mesozoic and Cenozoic stratigraphic sequences that are separated by an angular unconformity, which represents a regionally correlative peneplanation surface. Mesozoic strata are characterized by northwest and south–southeast‐derived thick clast‐supported conglomerates (Jurassic) overlain by fine‐grained lacustrine and alluvial deposits containing few fluvial channels (Cretaceous). Cenozoic deposits consist of dominantly alluvial fan and fluvial sediments shed from adjacent mountain ranges during the Oligocene–Holocene. The basin is still receiving sediment today, but is actively deforming and closing. Outwardly propagating thrust faults bound the ranges, whereas within the basin, active folding and thrusting occurs within two marginal deforming belts. Consequently, active fan deposition has shifted towards the basin centre with time, and previously deposited sediment has been uplifted, eroded and redeposited, leading to complex facies architecture. The geometry of folds and faults within the basin and the distribution of Mesozoic sediments suggest that the basin formed as a series of extensional half‐grabens in the Jurassic–Cretaceous which have been transpressionally reactivated by normal fault inversion in the Tertiary. Other clastic basins in the region may therefore also be inherited Mesozoic depocentres. The Dzereg Basin is a world class laboratory for studying competing processes of uplift, deformation, erosion, sedimentation and depocentre migration in an actively forming intracontinental transpressional basin.     

Making Space for Failure in Geographic Research

The idea that field research is an inherently “messy” process has become widely accepted by geographers in recent years. There has thus far been little acknowledgment, however, of the role that failure plays in doing human geography. In this article we push back against this, arguing that failure should be recognized as a central component of what it means to do qualitative geographical field research. This article seeks to use failure proactively and provocatively as a powerful resource to improve research practice and outcomes, reconsidering and giving voice to it as everyday, productive, and necessary to our continual development as researchers and academics. This article argues that there is much value to be found in failure if it is critically examined and shared, and—crucially—if there is a supportive space in which to exchange our experiences of failing in the field.     

A SAURON look at galaxy bulges

Kinematic and population studies show that bulges are generally rotationally flattened systems similar to lowluminosity ellipticals. However, observations with state‐of‐the‐art integral field spectrographs, such as SAURON, indicate that the situation is much more complex, and allow us to investigate phenomena such as triaxiality, kinematic decoupling and population substructure, and to study their connection to current formation and evolution scenarios for bulges of early‐type galaxies. We present the examples of two S0 bulges from galaxies in our sample of nearby galaxies: one that shows all the properties expected from classical bulges (NGC5866), and another case that presents kinematic features appropriate for barred disk galaxies (NGC7332). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)