Untersuchungen über Quelle und Ausbreitung der atmosphärischen Unruhe

Zusammenfassung Es wird die Herkunftsrichtung und Ausbreitungs-geschwindigkeit kurzperiodischer Luftdruckwellen mit Periodendauern von wenigen Sekunden und Amplituden von 10^–4 bis 10^–3 mm Hg untersucht. Zu diesem Zwecke wurden an drei zirka 800 m voneinander entfernten Punkten empfindliche Variographen aufgestellt und deren Meßwerte drahtlos an eine zentrale Registrierstation übertragen und registriert. Die gefundene Herkunftsrichtung der Luftdruckwellen weist vorwiegend nach NW, während die Ausbreitungsgeschwindigkeit zeitweise höher als Schallgeschwindigkeit ist. Ein Vergleich mit der jeweils herrschenden Wetterlage führt auf Beziehungen zwischen der gefundenen Herkunftsrichtung und dem Auftreten von Tiefdruckgebieten über dem Atlantik. Mögliche Ursachen sowie die Ausbreitung solcher Druckwellen in der Atmosphäre werden diskutiert.

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Summary There is investigated the direction of approach and the velocity of propagation of pressure waves of periods of a few seconds and amplitudes of 10^–4 to 10^–3 mm Hg. For this purpose three sensible variographs have been mounted at places distant ca. 800 m from each other; their indications were transmitted by wireless to a central station and recorded here. The direction of approach of the pressure waves was predominantly from NW, whereas the velocity of propagation temporarily is higher than the velocity of sound. Comparing the weather situation for the time there is a relation between the direction of approach and the appearence of low pressure areas on the Atlantic Ocean. Possible causes and the propagation of the pressure waves in the atmosphere are discussed.

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Résumé L'étude porte sur la direction d'ou proviennent les ondes de pression dont la période est de quelques secondes et l'amplitude comprise entre 10^–4 et 10^–3 mm, ainsi que sur leur vitesse de propagation. On a placé dans ce but en des points distants d'environ 800 m trois variographes sensibles dont les mesures étaient transmises par radio à une station centrale ou elles étaient enregistrées. L'azimut d'origine est essentiellement le Nord-Ouest; la vitesse de propagation était parfois supérieure à celle du son. Il existe une relation entre l'azimut d'origine et l'apparition de domaines dépressionnaires sur l'Atlantique. On examine enfin les causes possibles de ces ondes ainsi que leur propagation dans l'atmosphère.

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Mit 17 Textabbildungen.     

Vector fragility surfaces for reinforced concrete frames in Europe

Traditional approaches to damage estimation in earthquake loss modelling make use of relationships between scalar intensity measures and scalar engineering demand parameters. In this study we present a series of vector-valued fragility surfaces computed for low- and mid-rise reinforced concrete frames typical of those found in Europe. The use of vectors of intensity measures can result in conditional standard deviations of logarithmic engineering demand parameters that are up to 50 % smaller than those from traditional scalar methods. These reductions have significant implications for the shapes of loss curves, particularly for long return periods. The most efficient vector corresponds to a combination of spectral acceleration and a spectral shape parameter, \(\langle \ln S_a, \ln N_p\rangle \) , when used to predict maximum interstorey drifts. The study also demonstrates that engineering demand parameters have significant heteroskedasticity with respect to various intensity measures and that this feature must be modelled correctly when constructing fragility curves. This feature of the models presented herein has not previously been accounted for during the development of fragility curves or surfaces.     

Assessment and Management Strategies for Ungulate Population in Jiangxi Matoushan National Nature Reserve: Predicting the Prey-base from Empirical Field Data

In order to investigate the feasibility of reintroducing the South China tiger (Panthera tigris amoyensis) in the Jiangxi Matoushan National Nature Reserve, field surveys were conducted to assess prey distribution in the reserve. Twelve permanent transects were set in three distinct functional zones from February to April 2012 and May to July 2013. A total of 112 ungulate signs were recorded on these transects. In addition, 20 camera traps were used to survey ungulates and predators in 2012, while the following year we extended the survey site by using 30 cameras. Overall, 6641 capture events on 2930 camera days were obtained, presenting a variety of ungulate species: muntjak (Muntiacus muntjak), tufted deer (Elaphodus cephalophus), serow (Capricornis sumatraensis) and wild boar (Sus scrofa). Population structure and composition of ungulates was compared in different functional zones using a single factor of variance analysis in SPSS software. Significant differences in the distribution of ungulates were recognized between the core zone and experimental zone, but not in other zones due to differences in habitat types and management practices of the nature reserve. Using ArcGIS analysis and Salford Predictive Modeler software, we ran several predictive models to understand which areas are most suitable for ungulates. We conclude that muntjac and wild boar are mainly distributed in the experimental zone, serow are more common in the core zone, while tufted deer are located evenly in the three functional zones. Finally, suggestions for effective and feasible management strategies and techniques for Matoushan National Nature Reserve were recommended based on the results and analysis in this study.     

Widespread strombolian eruptions of mid-ocean ridge basalt

Glassy lava fragments were collected in pushcores or using a small suction-sampler from over 450 sites along the Juan de Fuca Ridge, Blanco Transform Fault, Gorda Ridge, northern East Pacific Rise, southern East Pacific Rise, Fiji back-arc basin, and near-ridge seamounts in the Vance, President Jackson, Taney, and a seamount off southern California. The samples consist of angular glass fragments, limu o Pele, Pele's hair, and other fluidal fragments formed during pyroclastic eruptions. Since many of the sites are deeper than the critical point of seawater, fragmentation cannot be hydrovolcanic and caused by expansion of seawater to steam. The glass fragments have a wide range of MORB compositions, ranging from fractionated to primitive and from depleted to enriched. Enriched magmas, which have higher volatile contents, may form more abundant pyroclasts than depleted magmas. Eruptions with high effusion rates produce sheet flows and abundant pyroclasts whereas those with low effusion rates produce pillow ridges and few pyroclasts. This relation suggests that high effusion and conduit rise rates are coupled to high magmatic gas contents. The eruptions are mainly effusive with a minor strombolian bubble burst component. We propose that the gas phase is an added component of variable amounts of magmatic foam from the top of the magma reservoir. As the mixture of resident magma and foam rises in the conduit, the larger bubbles in the foam rise more quickly and sweep up the smaller bubbles nucleating and growing from the resident magma. On eruption, the process of bubble coalescence is more complete for the slower rising, gas-poor lavas that erupt as pillow lavas whereas the limu o Pele associated with sheet flow eruptions commonly contain several percent vesicles that avoided coalescence during ascent. The spatter erupted at the vent is quench granulated in seawater above the vent, reducing the pyroclast grainsize. The granulated spatter and limu o Pele fragments are then entrained in a rising plume of seawater heated by the eruption, which disperses them to distances as great as 5 km from the vent.     

Sources of in-situ 36Cl in basaltic rocks. Implications for calibration of production rates

In-situ cosmogenic ³⁶Cl production rates from spallation of Ca and K determined in several previously published calibration studies differ by up to 50%. In this study we compare whole rock ³⁶Cl exposure ages with ³⁶Cl exposure ages evaluated in Ca-rich plagioclase in the same 10 ± 3 ka lava sample taken from Mt. Etna (Sicily, 38° N). The exposure age of the sample was determined by K–Ar and corroborated by cosmogenic ³He measurements on cogenetic pyroxene phenocrysts. Sequential dissolution experiments showed that high Cl concentrations in plagioclase grains could be reduced from 450 ppm to less than 3 ppm after 16% dissolution. ³⁶Cl exposure ages calculated from the successive dissolution steps of this leached plagioclase sample are in good agreement with K–Ar and ³He age. Stepwise dissolution of whole rock grains, on the other hand, is not as effective in reducing high Cl concentrations as it is for the plagioclase. 330 ppm Cl still remains after 85% dissolution. The ³⁶Cl exposure ages derived are systematically about 30% higher than the ages calculated from the plagioclase. We could exclude contamination by atmospheric ³⁶Cl as an explanation for this overestimate. Magmatic ³⁶Cl was estimated by measuring a totally shielded sample, but was found to account for only an insignificant amount of ³⁶Cl in the case of the 10 ka whole rock sample. We suspect that the overestimate of the whole rock exposure age is due to the difficulty in accurately assessing all the factors which control production of ³⁶Cl by low-energy neutron capture on ³⁵Cl, particularly variable water content and variable snow cover. We conclude that some of the published ³⁶Cl spallation production rates might be overestimated due to high Cl concentrations in the calibration samples. The use of rigorously pretreated mineral separates reduces Cl concentrations, allowing better estimates of the spallation production rates.In the Appendix of this paper we document in detail the equations used. These equations are also incorporated into a ³⁶Cl calculation spreadsheet made available in the supplementary data.     

The potato in Ireland's evolving agrarian landscape and agri-food system

The scale, structure and impacts of food systems in Ireland have changed dramatically over the last several hundred years, predominantly since the mechanisation and intensification of farming began in the late nineteenth century. The transformation of the potato production system, which for the preceding century had dominated the Irish diet, was particularly dramatic. The time from the introduction of the potato c. 1600 to its catastrophic decline in the mid-1800s, represented a period of Irish agriculture distinctly at odds with what came before and after, involving as it did complete dependence on a single crop system. Despite devastating crop losses suffered in the nineteenth century and particularly associated with the Great Famine, the potato remained agriculturally significant in Ireland. From the late 1800s onwards the system underwent a transition towards the highly mechanised, specialised, intensive and market-oriented agri-industrial food systems of today. This new high input-high output system was accompanied by an expansion in environmental impacts extending from local to global scales. This article addresses that transition in the role and impacts of the potato in Ireland, from its introduction to the present day.     

WOMEN GEOGRAPHERS IN BUSINESS AND GOVERNMENT: A SURVEY

A survey of women AAG members in applied geography shows a geographical concentration in the Washington metropolitan area and an employment concentration in the private sector. The typical educational preparation is a master's degree. Job titles reflect the importance of planning, environmental issues, and cartography; cartography is cited as the most helpful career skill. Respondents want the AAG to promote geography and to help graduates in finding careers.     

The response of flow duration curves to afforestation

The hydrologic effect of replacing pasture or other short crops with trees is reasonably well understood on a mean annual basis. The impact on flow regime, as described by the annual flow duration curve (FDC) is less certain. A method to assess the impact of plantation establishment on FDCs was developed. The starting point for the analyses was the assumption that rainfall and vegetation age are the principal drivers of evapotranspiration. A key objective was to remove the variability in the rainfall signal, leaving changes in streamflow solely attributable to the evapotranspiration of the plantation. A method was developed to (1) fit a model to the observed annual time series of FDC percentiles; i.e. 10th percentile for each year of record with annual rainfall and plantation age as parameters, (2) replace the annual rainfall variation with the long term mean to obtain climate adjusted FDCs, and (3) quantify changes in FDC percentiles as plantations age. Data from 10 catchments from Australia, South Africa and New Zealand were used. The model was able to represent flow variation for the majority of percentiles at eight of the 10 catchments, particularly for the 10–50th percentiles. The adjusted FDCs revealed variable patterns in flow reductions with two types of responses (groups) being identified. Group 1 catchments show a substantial increase in the number of zero flow days, with low flows being more affected than high flows. Group 2 catchments show a more uniform reduction in flows across all percentiles. The differences may be partly explained by storage characteristics. The modelled flow reductions were in accord with published results of paired catchment experiments. An additional analysis was performed to characterise the impact of afforestation on the number of zero flow days (N_zero) for the catchments in group 1. This model performed particularly well, and when adjusted for climate, indicated a significant increase in N_zero. The zero flow day method could be used to determine change in the occurrence of any given flow in response to afforestation. The methods used in this study proved satisfactory in removing the rainfall variability, and have added useful insight into the hydrologic impacts of plantation establishment. This approach provides a methodology for understanding catchment response to afforestation, where paired catchment data is not available.