A comparison of recent reanalysis datasets using objective feature tracking: Storm tracks and tropical easterly waves

Data from four recent reanalysis projects [ECMWF, NCEP-NCAR, NCEP - Department of Energy ( DOE), NASA] have been diagnosed at the scale of synoptic weather systems using an objective feature tracking method. The tracking statistics indicate that, overall, the reanalyses correspond very well in the Northern Hemisphere (NH) lower troposphere, although differences for the spatial distribution of mean intensities show that the ECMWF reanalysis is systematically stronger in the main storm track regions but weaker around major orographic features. A direct comparison of the track ensembles indicates a number of systems with a broad range of intensities that compare well among the reanalyses. In addition, a number of small-scale weak systems are found that have no correspondence among the reanalyses or that only correspond upon relaxing the matching criteria, indicating possible differences in location and/or temporal coherence. These are distributed throughout the storm tracks, particularly in the regions known for small-scale activity, such as secondary development regions and the Mediterranean. For the Southern Hemisphere (SH), agreement is found to be generally less consistent in the lower troposphere with significant differences in both track density and mean intensity. The systems that correspond between the various reanalyses are considerably reduced and those that do not match span a broad range of storm intensities. Relaxing the matching criteria indicates that there is a larger degree of uncertainty in both the location of systems and their intensities compared with the NH. At upper-tropospheric levels, significant differences in the level of activity occur between the ECMWF reanalysis and the other reanalyses in both the NH and SH winters. This occurs due to a lack of coherence in the apparent propagation of the systems in ERA15 and appears most acute above 500 hPa. This is probably due to the use of optimal interpolation data assimilation in ERA15. Also shown are results based on using the same techniques to diagnose the tropical easterly wave activity. Results indicate that the wave activity is sensitive not only to the resolution and assimilation methods used but also to the model formulation.

Isotopes and individuals: diet and mobility among the medieval Bishops of Whithorn

Stable isotopes get personal in this analysis of burials at a medieval cathedral. Compared with the local meat-eating rank and file, those people identified as bishops consumed significantly more fish and were incomers from the east. These results, while not so surprising historically, lend much increased confidence that isotope analysis can successfully read the status and mobility of individuals in a cemetery.

Holocene tidal palaeochannels, Severn Estuary Levels, UK: a search for granulometric and foraminiferal criteria

Holocene tidal palaoechannels, Severn Estuary Levels, UK: a search for granulometric and foraminiferal criteria. Proceedings of the Geologists' Association, 117, 329-344. Grain-size characteristics (by laser granulometry) and foraminiferal assemblages have been established for silts accumulated in five, dissimilar tidal palaeochannels of mid or late Holocene age in the Severn Estuary Levels, representative of muddy tidal systems. For purposes of general comparison, similar data were obtained from a representative active tidal inlet in the area, but all of these channels have been subject to human interference and are not relied upon as a model for environmental interpretation. Although the palaeochannel deposits differ substantially in their bedding characteristics and stratigraphical relationships from the level-bedded salt-marsh platform and mudflat deposits with which they are associated, and although the channel environment is distinctive morphologically and hydraulically, no critical textural differences could be found between the channel deposits and the associated facies. Similarly, no foraminiferal assemblages distinctive of a tidal channel were encountered. Instead, the assemblages compare with those from mudflats and salt-marsh platforms. It is concluded that the sides of the subfossil channels carried some vegetation, as was observed to be the case in the modern inlet. An alternative approach is necessary if concealed palaeochannel deposits are to be recognized in muddy systems from limited numbers of subsurface samples. Although the palaeochannels afforded no characteristic textural signature, they yield transverse grain-size patterns pointing to coastal movements during their evolution. Concave-up trends suggest outward coastal building, whereas convex-up ones point to marsh-edge retreat.

Stable isotope evidence for 1500 years of human diet at the city of York, UK

We present here the results of a large-scale diachronic palaeodietary (carbon and nitrogen isotopic measurements of bone collagen) study of humans and animals from a single site, the city of York (U.K.) dating from the Roman period to the early 19th century The human sample comprises 313 burials from the cemeteries of Trentholme Drive and Blossom Street (Roman), Belle Vue House (Anglo-Saxon), Fishergate (High and Later Medieval), and All Saints, Pavement (Later and Post-Medieval). In addition, 145 samples of mammal, fish and bird bone from the sites of Tanner Row and Fishergate were analyzed. The isotope data suggest dietary variation between all archaeological periods, although the most significant change was the introduction of significant quantities of marine foods in the Medieval periods. These are first evident in the diet of a small group of individuals from the High Medieval cemetery at Fishergate, although they were consumed almost universally in the following periods. The human isotope values are also remarkable due to unusually elevated delta N-15 ratios that are not sufficiently explained by the comparably small enrichment in C-13 that accompanies them. We discuss the possible reasons behind this and the archaeological significance of the data set.

Diet and diversity at later medieval Fishergate: The isotopic evidence

We present the results of stable carbon and nitrogen isotope analysis of bone collagen for 155 individuals buried at the Later Medieval (13th to early 16th century AD) Gilbertine priory of St. Andrew, Fishergate in the city of York (UK). The data show significant variation in the consumption of marine foods between males and females as well as between individuals buried in different areas of the priory. Specifically, individuals from the crossing of the church and the cloister garth had consumed significantly less marine protein than those from other locations. Isotope data for four individuals diagnosed with diffuse idiopathic skeletal hyperostosis (DISH) are consistent with a diet rich in animal protein. We also observe that isotopic signals of individuals with perimortem sharp force trauma are unusual in the context of the Fishergate dataset. We discuss possible explanations for these patterns and suggest that there may have been a specialist hospital or a local tradition of burying victims of violent conflict at the priory. The results demonstrate how the integration of archaeological, osteological, and isotopic data can provide novel information about Medieval burial and society.

A well-posed integral equation formulation for three-dimensional rough surface scattering

We consider the problem of scattering of time-harmonic acoustic waves by an unbounded sound-soft rough surface. Recently, a Brakhage Werner type integral equation formulation of this problem has been proposed, based on an ansatz as a combined single- and double-layer potential, but replacing the usual fundamental solution of the Helmholtz equation with an appropriate half-space Green's function. Moreover, it has been shown in the three-dimensional case that this integral equation is uniquely solvable in the space L-2 (Gamma) when the scattering surface G does not differ too much from a plane. In this paper, we show that this integral equation is uniquely solvable with no restriction on the surface elevation or slope. Moreover, we construct explicit bounds on the inverse of the associated boundary integral operator, as a function of the wave number, the parameter coupling the single- and double-layer potentials, and the maximum surface slope. These bounds show that the norm of the inverse operator is bounded uniformly in the wave number, kappa, for kappa > 0, if the coupling parameter h is chosen proportional to the wave number. In the case when G is a plane, we show that the choice eta = kappa/2 is nearly optimal in terms of minimizing the condition number.