Application of an adaptive filtering technique to surface photometry of galaxies. I. The method tested on NGC 3379

This study reports on the results of the application of an adaptive filtering technique to the two-dimensional photometric mapping of galaxies. For this test we used the elliptical galaxy NGC 3379, which is a luminosity standard. Our plate material (B-band), obtained with the Tautenburg Schmidt telescope, was digitized with the Babelsberg microdensitometer and with the ESO PDS. The 2-D scans were reduced according to the Babelsberg Image Processing Systems, whose key feature is an adaptive filter called ‘H-Transform’. By comparing our results (E-W light profile and isophotal parameters) to the most recent studies of NGC 3379 (DE VAUCOULEURS and CAPACCIOLI 1979, and NIETO and VIDAL 1984), we found no systematic errors in the photometric calibration and in the reduction procedure, with typical mean residuals from the other studies not larger than ±0.05 B-mag up to a threshold of 1% of the night sky level on each plate. We also re-confirmed the geometrical properties of the galaxy. The new filtering technique proved quite efficient in reducing the noise, with negligible effects on the photometric and geometric characteristics of the star-like sources.     

Bowen ratio/energy balance technique for estimating crop net CO2 assimilation,and comparison with a canopy chamber

Summary This paper describes a Bowen ratio/energy balance (BREB) system which, in conjunction with an infra-red gas analyzer (IRGA), is referred to as BREB+ and is used to estimate evapotranspiration (ET) and net CO₂ flux (NCF) over crop canopies. The system is composed of a net radiometer, soil heat flux plates, two psychrometers based on platinum resistance thermometers (PRT), bridge circuits to measure resistances, an IRGA, air pumps and switching valves, and a data logger. The psychrometers are triple shielded and aspirated, and with aspiration also between the two inner shields. High resistance (1 000 ohm) PRT's are used for dry and wet bulbs to minimize errors due to wiring and connector resistances. A high (55 K ohm) fixed resistance serves as one arm of the resistance bridge to ensure linearity in output signals. To minimize gaps in data, to allow measurements at short (e.g., 5 min) intervals, and to simplify operation, the psychrometers were fixed at their upper and lower position over the crop and not alternated. Instead, the PRT's, connected to the bridge circuit and the data logger, were carefully calibrated together. Field tests using a common air source showed appartent effects of the local environment around each psychrometer on the temperatures measured. ET rates estimated with the BREB system were compared to those measured with large lysimeters. Daily totals agreed within 5%. There was a tendency, however, for the lysimeter measurements to lag behind the BREB measurements. Daily patterns ofNCF estimated with the BREB+ system are consistent with expectations from theories and data in the literature. Side-by-side comparisons with a stirred Mylar canopy chamber showed similarNCF patterns. On the other hand, discrepancies between the results of the two methods were quite marked in the morning or afternoon on certain dates. Part of the discrepancies may be attributed to inaccuracies in the psychrometric temperature measurements. Other possible causes include the highly artificial air turbulence in the canopy chamber and possible associated stomatal response. More work is necessary to identify conclusively the causes. In spite of these uncertainties, the BREB+ technique appears well suited for the automated and simultaneous tracking of photosynthetic performance and water economy of crops in their virtually undisturbed natural environment.To whom reprint requests should be sent.With 7 Figures     

Salt transport on islands in the Okavango Delta: Numerical investigations

This study uses a numerical model to investigate the groundwater flow and salt transport mechanisms below islands in the Okavango Delta. Continuous evapotranspiration on the islands results in accumulation of solutes and the formation of a saline boundary layer, which may eventually become unstable. A novel Lagrangian method is employed in this study and compared to other numerical methods. The numerical results support the geophysical observations of density fingering on Thata Island. However, the process is slow and it takes some hundreds of years until density fingering is triggered. The results are sensitive to changes of the hydraulic gradient and the evapotranspiration rate. Small changes may lead to different plume developments. Results further demonstrate that density effects may be entirely overridden by lateral flow on islands embedded in a sufficiently high regional hydraulic gradient.     

Operationalizing climate targets under learning: An application of cost-risk analysis

Reviewing the existing studies of public perception and drawing analogies from other risk technologies, this paper explores the public positions on research and implementation of geoengineering as a means to combat climate change. Existing studies on geoengineering perceptions show low levels of awareness and a lack of knowledge. Hence, existing attitudes on geoengineering can be judged instable and stimulus-dependent. When judged in isolation, at least one third favors the use of geoengineering technologies preferring CDR over SRM technologies; when judged in comparison to other climate mitigation options, approval rates lose considerably support. Moreover, people seem to cautiously support research but oppose deployment while attitude formation depends on personal values and belief systems. The results of the empirical studies were fed into a Delphi workshop with experts for reflecting on the future development of public opinion and for designing a communication and public involvement process that corresponds to the empirical insights gained from the perception studies.     

Tropical precipitation, SSTs and the surface energy budget: a zonally symmetric perspective

The relative importance of sea surface temperatures (SSTs) and the surface energy budget to tropical precipitation is examined by comparing models with zonally symmetric climates, both fixed SST and coupled to a slab mixed layer ocean. Two models are considered with differing surface flux formulations and in each case solutions that are symmetric about the equator are perturbed to create interhemispheric asymmetry. When SSTs are prescribed in the two models with different flux formulations, the magnitude of tropical precipitation response to identical SST anomalies is significantly different, but the differences can be understood in terms of the altered surface fluxes. In contrast, when the net surface energy fluxes are constrained to be identical in mixed layer simulations of the two different models, the response of tropical precipitation to perturbations in the surface energy balance is very similar. Both perspectives predict qualitatively the same precipitation response, but the energy budget better predicts the magnitude of the precipitation response. Thus, we argue that the atmospheric energy budget, controlled in these experiments primarily by the surface energy budget, is more fundamental to the control of tropical precipitation than the SSTs, in these simulations with axisymmetric climates. We touch briefly on a complication in the interpretation of the model results due to the fact that fixed SST and slab-ocean versions of the model can produce different Hadley cell strengths for the same SSTs.     

A global perspective on African climate

We describe the global climate system context in which to interpret African environmental change to support planning and implementation of policymaking action at national, regional and continental scales, and to inform the debate between proponents of mitigation v. adaptation strategies in the face of climate change. We review recent advances and current challenges in African climate research and exploit our physical understanding of variability and trends to shape our outlook on future climate change. We classify the various mechanisms that have been proposed as relevant for understanding variations in African rainfall, emphasizing a “tropospheric stabilization” mechanism that is of importance on interannual time scales as well as for the future response to warming oceans. Two patterns stand out in our analysis of twentieth century rainfall variability: a drying of the monsoon regions, related to warming of the tropical oceans, and variability related to the El Niño–Southern Oscillation. The latest generation of climate models partly captures this recent continent-wide drying trend, attributing it to the combination of anthropogenic emissions of aerosols and greenhouse gases, the relative contribution of which is difficult to quantify with the existing model archive. The same climate models fail to reach a robust agreement regarding the twenty-first century outlook for African rainfall, in a future with increasing greenhouse gases and decreasing aerosol loadings. Such uncertainty underscores current limitations in our understanding of the global climate system that it is necessary to overcome if science is to support Africa in meeting its development goals.     

The domestic divide: Access to the Internet in New Zealand

We use unit records of the 2006 census to show that access to the Internet in the home varies geographically in New Zealand primarily as a result of demographic and socio‐economic differences among individuals. Of particular significance is the much lower rates of domestic access experienced by Māori and Pacific Island individuals even after controlling for differences in their age, gender, education, income, occupation and settlement type. While differences in Internet access by ethnicity has been noted before, it is the magnitude and persistence of this difference in New Zealand after controlling for correlated factors that renders this study unique. Our results have important implications in an education environment increasingly reliant on Web access, but they also raise questions about the extent of access to the Internet outside the home.     

临界转换的早期预警信号

从生态系统到金融市场和气候在内的很多复杂动力系统,都会有临界点,在这样的点上系统可能会发生突变,从而演变到一个对立的动力模式上。在这样的临界点到达之前对其进行预测极为困难,但是现在,不同科学领域的研究工作表明,普遍性的早期预警信号有迹可循。对一系列不同类型的系统来说,这些信号会指示是否正在趋近一个临界阈值。     

Beitrag zu einer Definition für Starkregen im Ostalpengebiet

Zusammenfassung Schon vor etlichen Jahren hat man die Unzulänglichkeiten der früheren Starkregendefinitionen klar formuliert (vor allem in England) und nunmehr durch die Betonung der Häufigkeitn eine verbesserte Definition gefordert. Mit Hilfe von deutschen Auswerteverfahren für Ombrographenregistrierungen wird in vorliegender Arbeit der Versuch unternommen, auf dieser neuen Basis eine für Österreich gültige, aber allgemein vergleichbare Definition der Starkregen zu finden, und es ergibt sich, daß als Starkregen in Österreich ein Regenfall zu bezeichnen ist, der die Intensität eines Idealregens erreicht oder überschreitet, der alle Jahre höchstens einmal in dieser Stärke an jeder Station des betreffenden Gebietes (aber natürlich nicht unbedingt überall gleichzeitig) vorkommen würde (n=1). AlsPlatzregen ist ein Regenfall anzusehen, der die Intensität eines höchstens alle zwei Jahre (n=1/2), und alsstarker Platzregen ein solcher, der die Intensität eines höchstens alle acht Jahre (n=1/8) vorkommenden Regens erreicht bzw. überschreitet. Auf eine formelmäßige Erfassung dieser Grenzkurve wird hier verzichtet, weil solcherart kaum ein einfacher und praktisch verwendbarer Ausdruck gegeben werden könnte; vielmehr werden die zu den festgelegtenn gehörigen Intensitätswerte für vier regengeographisch verschiedene Hauptgebiete Österreichs in einer Tabelle gegeben.

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Summary Already several years ago the definitions for heavy rainfall were strongly criticized as being insufficient (above all in England) and a better definition with emphasis on the frequency was claimed. Using German evaluation methods for rain-gauge records, this paper makes an attempt of finding a new definition for heavy rainfall being valid particularly for Austria, but comparable generally. It is concluded that, in Austria, a rainfall is to be defined as heavy rain which reaches or surpasses the intensity of an ideal rain occurring with that intensity at most once in a year at every station of the area in question, but not necessarily everywhere at the same time (n=1). A rainfall is considered as downpour if it reaches, respectively surpasses the intensity of a rain occurring at most once every two years (n=1/2), and as heavy downpour a case with an intensity occurring once every eight years at most (n=1/8). A formula of this limit curve is not given as there exists no simple and practically applicable expression for it. Intensity values, however, referring to then given above are presented in a table for four geographical rain areas of Austria.

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Résumé Il y a plusieurs années déjà on a souligné (en Angleterre surtout) les insuffisances des anciennes définitions des pluies de grande intensité et on en a suggéré une meilleure en mettant l'accent sur les fréquencesn. Utilisant le procédé allemand de dépouillement des enregistrements d'ombrographes, on tente ici de trouver sur cette nouvelle base une définition des pluies violentes, valable pour l'Autriche, mais permettant une comparaison générale. Il s'ensuit qu'en Autriche on considère comme pluie intense celle qui atteint ou dépasse l'intensité d'une «pluie idéale» qui se produirait au maximum une fois chaque année (n=1) avec cette intensité en chaque station de la région en question (mais pas nécessairement partout en même temps). Unepluie intense ou battante (Platzregen) est celle qui atteint ou dépasse la pluie maximum de deux ans (n=1/2), et unepluie torrentielle (starker Platzregen) celle qui atteint ou dépasse le maximum de huit ans (n=1/8). On renonce ici à préciser numériquement les limites de ces différents cas, car on ne pourrait donner une expression analytique simple et pratique; on se borne donc à présenter sous forme de tableau pour quatre régimes pluvieux d'Autriche les valeurs de l'intensité de pluie correspondant aux différentes valuers den.

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Mit 6 Textabbildungen.     

Public climate-change skepticism,energy preferences and political participation

Many studies have shown a general decline of public concern about climate change or vice versa a rise in public climate-change skepticism, in particular in the U.S. and other Anglo-Saxon countries. There is a vivid debate on whether this is a global phenomenon, on which factors explain the decline, and on the broader societal implications of these trends in the context of the transformation toward a low-carbon society. We add to this literature by presenting the results of a recent general population survey in Germany in which we looked for systematic linkages between public climate-change skepticism on one hand, and energy preferences and political participation on the other. Germany is an interesting testbed as it is currently involved in a large-scale restructuring of its system of energy supply toward renewable energy sources (the “Energiewende”). Our results indicate that climate-change skepticism has not diffused widely in Germany, but that it correlates with less support of renewable energy sources. However, skepticism correlates negatively with political participation, and there is no strong political outlet for public climate-change skepticism in Germany. Alternative potential barriers for the successful implementation of the “Energiewende” are also discussed.