Croatia in the continental traffic network of Europe

Croatia is located on the southeastern edge of Central Europe (Ruppert 1995), between the navigable Danube River and the Adriatic Sea, so that participates not only in continental traffic, but in the maritime and river traffic of Europe as well.Although the transit position of Croatia is very favorable, transportation itself has unfortunately not been developed in accordance with these advantages. This is a result of the social-economic, especially political, development of the region in the course of its history. Unfortunately, politics also influences the selection of transit routes in this part of Europe today. With the break-up of socialist states, particularly the former Yugoslavia, new states have appeared which are seeking their place in the European traffic network. Because of the momentarily uncertain political circumstances, the construction of some transit routes in Croatia have not been foreseen in international developmental plans for continental transit, despite the fact that they would be logically expected given the advantages of their position.     

Intermittent Trajectories in the 3/1 Jovian Resonance

The statistical behaviour of intermittent trajectories at the 3/1resonance is investigated. The elliptic planar restricted three-body problemis used as a model. Distribution functions for time intervals D betweeneccentricity bursts are obtained and theoretically interpreted. For smallervalues of D the distribution is found to be of Poisson type, while in itstail it is described by a power law D. This change in thedistribution occurs for values of D in the range10⁵10⁶Jupiter periods. The power-lawindexfor the integral distributions lies in the range (-2,-1) and istrajectory dependent. The algebraic decay in the tails of the distributionsis explained by the phenomenon of sticking of orbits to the chaos borderduring long intervals between bursts.     

Bemerkungen zur Hypothese zweier Sturmzeitringströme

Summary For several years the theory of the main phase of geomagnetic storms takes into account the existence of two storm time ring currents which are thought to exist in different altitudes. This hypothesis is supported less by satellite data than by the analysis of recovery effects observed in the geomagnetic records, according to that the recovery phase should exist of two seperate single phases. In our opinion however the observational material seems not convincing enough, especially because material of one station only was used for the hitherto made investigations and no elimination of theSq-part was executed. A critical analysis of the observational material is by all means necessary, especially for the reason that already in literature extensive inferences of theDR2 ring current for the formation and the energy behaviour of theDP part were drawn. For the investigation of recovery effects it is necessary to use additionally to records of equatorial stations those of observatories in higher latitudes. TheSq-part has to be eliminated in the analysis. It is referred that new disturbances after the beginning of the recovery phase can feign two separated ring current effects. Some examples of the recovery phase will be discussed. They show that the observational material gives no necessity for the supposition of two separate strom time ring currents. Furthermore some theoretical considerations are opposite to this hypothesis. The charge exchange with thermical atoms of hydrogen is discussed to be a possible loss process. It is taken into account also the possibility to suppose a wide proton energy spectrum for explaining the recovery phase.

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Mitteilung aus dem Geomagnetischen Institut Potsdam, Nr. 226.     

Turbulence and zooplankton production: insights from PROVESS

Zooplankton are directly influenced by turbulence in both a passive and an active manner. Passively, zooplankton are at the mercy of turbulence in how it affects their vertical mixing, encounter rate, detection abilities and feeding current efficiency. Many zooplankton species, however, are actively able to mitigate the effects of turbulence by modifying their behaviour, e.g. vertical migration, prey switching and habituation to hydromechanical stimuli. Both theoretical treatments of these processes and field observations from the northern North Sea are examined. Field observations show that some copepod species actively migrate to avoid high turbulence levels in surface waters. Furthermore, observations show a negative relationship between turbulence and zooplankton ingestion rates. This supports the paradigm of a dome-shaped response for zooplankton production with environmental turbulence. A theoretical treatment shows that the reaction distance, R, for an ambush-feeding copepod feeding on swimming organisms follows R ∝ ^−1/6 where is the turbulent dissipation rate, a result that shows close agreement with previously reported experimental results.     

Turbulent mixing in the Northern North Sea: a numerical model study

The aim of this study is to intervalidate observations and numerical simulation results for the turbulent dissipation rate under strong wind conditions in the Northern North Sea during one week in October 1998. The observations were obtained by spatially and temporally averaging measurements of small-scale shear with a free-falling shear probe. The 1D numerical model used for this study is based on a state-of-the-art two-equation k− turbulence model with an algebraic second-moment closure scheme. It is discussed by means of annual and seasonal model simulations how the influence of heat and salt advection and internal waves can be accounted for. After these precautions, the agreement between observations and simulations of the turbulent dissipation rate are fairly good. Remaining differences cannot only be explained by problems such as undersampling and noise level, but also by idealising model assumptions.     

Kritische Bemerkungen zur Berechnung der «Awahren Höhen»

Zusammenfassung Im ersten Teil werden Bedingungen angegeben, unter denen eine eindeutige Lösung der Integralgleichung der scheinbaren Höhe erhalten werden kann. Der zweite Teil befasst sich mit den sich hieraus ergebenden Folgerungen. Im letzten Abschnitt werden eventuelle Fehlerquellen einiger Verfahren, die zur Zeit angewendet werden, untersucht und Verbesserungsvorschläge gemacht.

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Summary In the first part the conditions are given under which the integral equation of the virtual height can be resolved in an unambiguous way. In the second part some conclusions of these conditions are discussed. Finally in the last part we discuss procedures which are actually used; some sources of possible errors are indicated and proposals to improve them are made.

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Die Arbeit wurde durch eine Forschungsbeihilfe des Bundesministeriums für Wirtschaft, Nr. A 190, ermöglicht.     

Projection of runoff characteristics as a response to regional climate change in a Central/Eastern European catchment

ABSTRACT

The impact of climate change on runoff characteristics is investigated for the Upper Tisza basin, in eastern Central Europe. For a reliable estimation of uncertainty, an appropriate stochastic weather generator is embedded into a Monte Carlo cycle capable of generating any large number of independent, equally probable, 100-year-long daily sequences of synthetic data with which a hydrological model is driven in order to obtain the hydrological responses to the meteorological data sequences. According to our results, a decrease of daily average runoff is likely to occur in the future in the Upper Tisza basin, especially in July and August. The occurrence of water levels below the critical low level is estimated to increase between July and October. Level-3 flood warnings are projected to be less frequent in the future; however, they will tend to be more severe than in the historical period.     

Zur Dynamik von Seichtgewässern

Ohne Zusammenfassung