Funkeigenpeilung,ihre Vorteile und ihre Grenzen

Zusammenfassung Die vom Nautiker grundsätzlich bevorzugte Eigenpeilung erhält bei Einsatz des Sichtfunkpeilers an Bord erweiterte Anwendungsmöglichkeiten (größere Reichweiten, Peilmöglichkeit bei Störsendern und starken atmosphärischen Störungen, kompaßunabhängige Zielfahrt und Standortsbestimmung). Für die Erzielung größter Reichweiten und für Dämmerungs- und Nachtpeilungen ist man beim heutigen Stand der Technik noch auf Fremdpeilungen mit Adcockpeilern angewiesen. Im Grenzwellenbereich können optimale Peilergebnisse auch nur durch Fremdpeilungen mit Adcockpeilern erzielt werden. Für die Aufgaben, bei denen auf Eigenpeilungen im Grenzwellengebiet nicht verzichtet werden kann, ist die Verwendung von Sichtfunkpeilern von besonderem Vorteil.

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Radio sell-bearings, their advantages and limitations

Summary The applicability of self-bearings (which are, on principle, preferred by navigators) is greatly extended by using the Visual Direction Finder on board ships (longer ranges; possibility to take bearings even in the presence of interfering transmitters and atmospherics; possibility of homing and position finding independent of the compass). For obtaining maximum ranges and for taking bearings during the dark and twilight hours, it is still necessary at the present state of technics, to take bearings from the ground by means of Adcock systems. Also in the wave band between 100 and 200 m (coastal band), optimum results can be obtained only with the aid of ground bearings by means of Adcock direction finders. For such problems which require self-bearings in the coastal band, it is of particular advantage to employ Visual Direction Finders.

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Radiogoniométrie de bord — Avantages et limites

Résumé Les navigateurs préfèrent en général la radiogoniométrie de bord à la goniométrie au sol. Un goniomètre cathodique offre des possibilités tout à fait nouvelles à la goniométrie de bord, c. à. d. portées plus étendues — radio-goniométrie même en présence d'émetteurs perturbateurs ou de parasites atmosphériques — navigation vers un but indépendamment du compas — détermination du point de navire. A l'état actuel de la technique on est encore obligé d'employer la radiogoniométrie au sol au moyen d'appareils Adcock pour obtenir les plus grandes portées possibles et pour la goniométrie nocturne. En outre, ce n'est qu'en se servant de la radiogoniométrie Adcock au sol qu'on a dans la gamme d'ondes minima des portées maxima. Dans les cas où on ne peut pas renoncer dans la gamme des ondes minima à la radiogoniométrie de bord l'emploi du goniomètre cathodique est particulièrement avantageux.

     

Climate change,the monsoon,and rice yield in India

Recent research indicates that monsoon rainfall became less frequent but more intense in India during the latter half of the Twentieth Century, thus increasing the risk of drought and flood damage to the country’s wet-season (kharif) rice crop. Our statistical analysis of state-level Indian data confirms that drought and extreme rainfall negatively affected rice yield (harvest per hectare) in predominantly rainfed areas during 1966–2002, with drought having a much greater impact than extreme rainfall. Using Monte Carlo simulation, we find that yield would have been 1.7% higher on average if monsoon characteristics, especially drought frequency, had not changed since 1960. Yield would have received an additional boost of nearly 4% if two other meteorological changes (warmer nights and lower rainfall at the end of the growing season) had not occurred. In combination, these changes would have increased cumulative harvest during 1966–2002 by an amount equivalent to about a fifth of the increase caused by improvements in farming technology. Climate change has evidently already negatively affected India’s hundreds of millions of rice producers and consumers.     

Sensitivity of boreal forests to possible climatic warming

General circulation models indicate substantial CO₂ warming in high latitudes. In these regions, which include the boreal coniferous forests, the activity of ecosystems is largely controlled by temperature. The effective temperature sum (degree-days) is used in this study for describing the regional variability in the productivity of boreal ecosystems. Although the concept is simple, it takes into account two basic factors: the length of the growing season and the day-to-day level of activity of the ecosystem. This study examines which areas in the boreal coniferous forests would be most sensitive to a possible climatic warming. The data used in the study are for Finland.A regression is estimated between regional forest growth rate and effective temperature sum. A climatic warming is assumed and the corresponding growth response is calculated, using the regression, for northern and southern areas, and for maritime and continental areas. The response is expressed in terms of (i) absolute increase in growth (grams per m² per year) and (ii) relative increase in growth. The results indicate that a given climatic warming would yield the greatest absolute increase in growth in warm (i.e. southern) and maritime parts of the biome. In terms of the relative growth response the sensitivity would increase northward and toward maritime areas.     

Basin‐scale fluvial correlation and response to the Tethyan marine transgression: An example from the Triassic of central Spain

The relationships between large‐scale depositional processes and the stratigraphic record of alluvial systems, e.g. the origin and distribution of channel stacking patterns, changing architecture and correlation of strata, are still relatively poorly understood, in contrast to marine systems. We present a study of the Castillian Branch of the Permo‐Triassic Central Iberian Basin, north‐eastern Spain, using chemostratigraphy and a detailed sedimentological analysis to correlate the synrift Triassic fluvial sandstones for ~80 km along the south‐eastern basin margin. This study investigates the effects of Middle Triassic (Ladinian) Tethyan marine transgression on fluvial facies and architecture. Chemostratigraphy identifies a major, single axially flowing fluvial system lasting from the Early to Middle Triassic (~10 Ma). The fluvial architecture comprises basal conglomerates, followed by amalgamated sandstones and topped by floodplain‐isolated single‐ or multi‐storey amalgamated sandstone complexes with a total thickness up to ~1 km. The Tethyan marine transgression advanced into the basin with a rate of 0.04–0.02 m/year, and is recorded by a transition from the fluvial succession to a series of maximum flooding surfaces characterised by marginal marine clastic sediments and sabkha evaporites. The continued, transgression led to widespread thick carbonate deposition infilling the basin and recording the final stage of synrift to early‐post‐rift deposition. We identify the nonmarine to marine transition characterised by significant changes in the Buntsandstein succession with a transition from a predominantly tectonic‐ to a climatically driven fluvial system. The results have important implications for the temporal and spatial prediction of fluvial architecture and their transition during a marine transgression.     

Lateral terrestrial water flow contribution to summer precipitation at continental scale – A comparison between Europe and West Africa with WRF-Hydro-tag ensembles

It is well accepted that summer precipitation can be altered by soil moisture condition. Coupled land surface – atmospheric models have been routinely used to quantify soil moisture – precipitation feedback processes. However, most of the land surface models (LSMs) assume a vertical soil water transport and neglect lateral terrestrial water flow at the surface and in the subsurface, which potentially reduces the realism of the simulated soil moisture – precipitation feedback. In this study, the contribution of lateral terrestrial water flow to summer precipitation is assessed in two different climatic regions, Europe and West Africa, for the period June–September 2008. A version of the coupled atmospheric-hydrological model WRF-Hydro with an option to tag and trace land surface evaporation in the modelled atmosphere, named WRF-Hydro-tag, is employed. An ensemble of 30 simulations with terrestrial routing and 30 simulations without terrestrial routing is generated with random realizations of turbulent energy with the stochastic kinetic energy backscatter scheme, for both Europe and West Africa. The ensemble size allows to extract random noise from continental-scale averaged modelled precipitation. It is found that lateral terrestrial water flow increases the relative contribution of land surface evaporation to precipitation by 3.6% in Europe and 5.6% in West Africa, which enhances a positive soil moisture – precipitation feedback and generates more uncertainty in modelled precipitation, as diagnosed by a slight increase in normalized ensemble spread. This study demonstrates the small but non-negligible contribution of lateral terrestrial water flow to precipitation at continental scale.     

Great-power politics,order transition,and climate governance: insights from international relations theory

The complex politics of climate change cannot be properly understood without reference to deeper geopolitical trends in the wider international system. Chief among these is the growing resurgence of ‘great-power politics’ between China and the US, along with failures of socialization and enmeshment into global governance structures in relation to these two powers. Traditional theoretical frameworks have failed to adequately account for these developments. Nonetheless, this current great-power contestation is at the core of an order transition that has prevented the large-scale institutional redesign required to remove deadlocks in existing global governance structures, including climate governance. Examples from the 2009 Copenhagen Climate Change Conference provide ample evidence for these claims. The slow progress of the climate change negotiations are due not just to the politics of the issue itself, but to the absence of a new political bargain on material power structures, normative beliefs, and the management of the order amongst the great powers. Without such a grand political bargain, which could be promoted through a forum of major economies whose wide-ranging remit would go beyond single issues, the climate change regime is only ever likely to progress in a piecemeal fashion.

Policy relevance

Despite the achievements of the 2012 Doha Climate Change Conference, the climate negotiations are not on course to limit warming to 2 °C, and thereby avoid ‘dangerous’ climate change. Several factors have been invoked to account for such slow progress: notably, the nature of the climate change problem itself, the institutional structure of the climate regime, and lack of political will among key players. An alternative explanation is proposed such that the failure to seriously address climate change – as well as other global problems – reflects a resurgent meta-struggle between the ‘great powers’ of China and the US over the nature of the global order. Without such a broader understanding of the deeper dynamics underlying the stalemates of the climate change negotiations, there is little chance of turning those negotiations around.     

Observation of snowfall with a low-power FM-CW K-band radar (Micro Rain Radar)

Quantifying snowfall intensity especially under arctic conditions is a challenge because wind and snow drift deteriorate estimates obtained from both ground-based gauges and disdrometers. Ground-based remote sensing with active instruments might be a solution because they can measure well above drifting snow and do not suffer from flow distortions by the instrument. Clear disadvantages are, however, the dependency of e.g. radar returns on snow habit which might lead to similar large uncertainties. Moreover, high sensitivity radars are still far too costly to operate in a network and under harsh conditions. In this paper we compare returns from a low-cost, low-power vertically pointing FM-CW radar (Micro Rain Radar, MRR) operating at 24.1?GHz with returns from a 35.5?GHz cloud radar (MIRA36) for dry snowfall during a 6-month observation period at an Alpine station (Environmental Research Station Schneefernerhaus, UFS) at 2,650?m height above sea level. The goal was to quantify the potential and limitations of the MRR in relation to what is achievable by a cloud radar. The operational MRR procedures to derive standard radar variables like effective reflectivity factor (Z _e) or the mean Doppler velocity (W) had to be modified for snowfall since the MRR was originally designed for rain observations. Since the radar returns from snowfall are weaker than from comparable rainfall, the behavior of the MRR close to its detection threshold has been analyzed and a method is proposed to quantify the noise level of the MRR based on clear sky observations. By converting the resulting MRR-Z _e into 35.5?GHz equivalent Z _e values, a remaining difference below 1?dBz with slightly higher values close to the noise threshold could be obtained. Due to the much higher sensitivity of MIRA36, the transition of the MRR from the true signal to noise can be observed, which agrees well with the independent clear sky noise estimate. The mean Doppler velocity differences between both radars are below 0.3?ms^?1. The distribution of Z _e values from MIRA36 are finally used to estimate the uncertainty of retrieved snowfall and snow accumulation with the MRR. At UFS low snowfall rates missed by the MRR are negligible when comparing snow accumulation, which were mainly caused by intensities between 0.1 and 0.8 mm?h^?1. The MRR overestimates the total snow accumulation by about 7%. This error is much smaller than the error caused by uncertain Z _e?Csnowfall rate relations, which would affect the MIRA36 estimated to a similar degree.     

Inter‐ and intra‐colonial genotypic diversity in hermatypic hydrozoans of the family Milleporidae

Genetic diversity is the basis for adaptation and therefore of primary scientific interest, especially in species that are threatened by anthropogenic challenges, e.g. climate change and/or pollution. Coral reefs are among the most threatened but also the most diverse ecosystems and have therefore been studied quite extensively. So far, most investigations have focused on scleractinian corals while the equally important reef builders, the hydrozoans, have been less considered. Here we provide the first study of genotypic variability as well as intra‐colonial genetic variability, the co‐occurrence of more than one genotype within a single colony, in Milleporidae based on microsatellites. We analysed two geographically distinct populations from the Millepora dichotoma complex, one from the Red Sea and one from the Great Barrier Reef. Additionally, a population of Millepora platyphylla was analysed from French Polynesia. We compared microsatellite multilocus genotypes and cytochrome c oxidase subunit I haplotypes for each of the three field sites to detect levels of genotypic diversity at the intra‐ and inter‐specific levels. Furthermore, we examined all species for the occurrence of intra‐colonial genetic variability, a recently described mechanism in scleractinian corals that might enhance the adaptive potential of sessile organisms. We found both species and all field sites to be genotypically variable. Twelve mitochondrial haplotypes and 27 multilocus microsatellite genotypes were identified. In addition, intra‐colonial genetic variability was detected in the M. dichotoma complex from the Great Barrier Reef as well as in M. platyphylla from French Polynesia. All of the intra‐colonial genetically variable colonies consisted of one main genotype and a second divergent genotype caused by somatic mutations (mosaicism). Our study proves that Milleporidae are genetically variable and that the phenomenon of intra‐colonial genetic variability also occurs in this important reef‐building family.