Anomalous gradient winds in the subtropical jet stream and interpretations of forecast failures

Summary Dramatic examples of forecast failures in global models of moderate resolution (i.e., T106) have been shown to occur during periods of the negative phase of the Pacific/North American (PNA) pattern in the Northern Hemisphere winter. Specifically, in these periods forecast skills at 500hPa as measured by the standard anomaly correlation index dropped to rather low values by days 4 and 5 of the forecasts. This paper examines systematically some of the factors that may have contributed to the failure of these model forecasts.In particular, strong winds approaching intensities on the order of 100ms^–1 south of Japan at the 200hPa level were degraded by the initialization and data assimilation procedures of the models. These observed winds were found to be supergradient in nature and representative of the anomalous solution of the gradient wind equation. Procedures such as the multivariate optimum interpolation (with its geostrophic constraints) and the normal-mode initialization including several vertical modes apparently were factors that led to the degradation of these strong winds in the initial model states. In this paper, an analysis of these factors is presented, and it is shown that uninitialized analyses (with no constraints) based on a simple successive correction procedure can retain the strong winds evident in the observations. Forecasts thus performed appear to retain wave trains, a characteristic feature of negative PNA initial states, leading to a significant improvement in forecast skill.     

Benthic diatom community response to environmental variables and metal concentrations in a contaminated bay adjacent to Casey Station, Antarctica

This study examined the effects of anthropogenic contaminants and environmental variables on the composition of benthic diatom communities within a contaminated bay adjacent to an abandoned waste disposal site in Antarctica. The combination of geographical, environmental and chemical data included in the study explained all of the variation observed within the diatom communities. The chemical data, particularly metal concentrations, explained 45.9% of variation in the diatom communities, once the effects of grain-size and spatial structure had been excluded. Of the metals, tin explained the greatest proportion of variation in the diatom communities (28%). Tin was very highly correlated (R2>0.95) with several other variables (copper, iron, lead, and sum of metals), all of which explained similarly high proportions of total variation. Grain-size data explained 23% of variation once the effects of spatial structure and the chemical data had been excluded. The pure spatial component explained only 1.8% of the total variance. The study demonstrates that much of the compositional variability observed in the bay can be explained by concentrations of metal contaminants.     

The lateral distribution of extensive air showers produced by cosmic rays above 10 eV as measured by water- erenkov detectors

Measurements of the lateral distribution function (ldf) of Extensive Air Showers (EAS) as recorded by the array of water- erenkov detectors at Haverah Park are described, and accurate experimental parameterizations expressing the mean ldf for 2 × 10¹⁷ < E < 4 × 10¹⁸ eV, 50 < r < 700 m, and θ < 45° are given. An extrapolation of these relations to the regime E ≥ 10¹⁹ eV and r > 700 m is described: extrapolation in this energy domain appears valid, and an approximate correction term is given for the larger core distances. The results of recent Monte Carlo simulations of shower development and detector behavior are compared to the parameterized ldf. The agreement is good increasing confidence that these simulations may be trusted as design tools for the Auger project, a proposed ‘next generation’ detector system.     

Two new tungsten bearing horizons in the older precambrium of Rhodesia

In Rhodesia strata-bound tungsten deposits together with submarine metavolcanics can be found in two formations of the older Precambrium. In the lower portion of the Bulawayan formation (about 2900 million years) there is an horizon with W, Au, Sb, As and banded iron stones. The tungsten mineralisation consists of scheelite. In the Piriwiri formation (about 1950 million years) within the upper part of the Lomagundi system a tungsten horizon contains scheelite as well as wolframite. The scheelite mineralisations of both formations show ore fabrics like those described and illustrated by R. Höll, A. Maucher and H. Westenberger (1972) from two strata-bound scheelite deposits of the Eastern Alps. These deposits of the Alps (R. Höll 1971) belong to the Early Paleozoic. This is an age of many strata-bound deposits of the Sb-W-Hg-formation, which are also related to a submarine volcanism and associated with lineaments (a Circumpacific and an Eurasiatic-Mediterranean branch) along the margins of the ancient continents (A. Maucher 1965). Genetically the strata-bound tungsten mineralisations of the Bulawayan formation, the Piriwiri formation and the Early Paleozoic are very similar.

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Zusammenfassung In Rhodesien treten schichtgebundene Wolframvorkommen zusammen mit submarinen Metavulkaniten in zwei Zeitabschnitten des älteren Präkambriums auf. Die Vererzung im unteren Teil der Bulawayan Formation (etwa 2900 Millionen Jahre) führt W, Au, Sb, As und banded iron stones. Die Wolframmineralisation besteht aus Scheelit. In der Piriwiri Formation (rund 1950 Millionen Jahre) innerhalb des oberen Teils des Lomagundi Systems enthält ein Wolframhorizont sowohl Scheelit als auch Wolframit. Die Scheelitvererzung beider Formationen zeigt Gefüge, die mit jenen weitgehend übereinstimmen, die von R. Höll, A. Maucher und H. Westenberger (1972) von zwei schichtgebundenen Scheelitvorkommen der Ostalpen beschrieben und abgebildet wurden. Diese Vorkommen in den Alpen (R. Höll 1971) liegen im Altpaläozoikum, einem Zeitraum mit vielen schichtgebundenen Vorkommen der Sb-W-Hg-Formation, die ebenfalls auf einen submarinen Vulkanismus zu beziehen sind und mit Lineamenten (mit einem zirkumpazifischen und einem eurasiatisch-mediterranen Ast) an den Rändern der alten Kontinente in Verbindung stehen (A. Maucher 1965). Genetisch sind die schichtgebundenen Scheelitvererzungen der Bulawayan Formation, der Piriwiri Formation und des Altpaläozoikums einander sehr ähnlich.