Quantifying volume transports during SKAGEX with the Norwegian Ecological Model system

A coupled 3-dimensional physical, chemical and biological model system, NORWECOM (the NORWegian ECOlogical Model system), is validated and used to identify and quantify the short-term variability of the different water masses being transported into and out of Skagerrak. The model system is a nesting between a coarse grid model set up for an extended North Sea, and a fine grid defined in the Skagerrak/Kattegat area.Originating from the extensive SKAGEX (SKAGerrak EXperiment) database, several interesting events have been identified and become the focus of the modeling. Through interactive use of the SKAGEX data set and NORWECOM, it is possible to gain a new insight into a very complex hydrodynamic system, an insight that is hard to achieve based on measurements only.     

Retrieval of effective cloud field parameters from radiometric data

Theoretical and Applied Climatology - This study presents evaluation of the ability of Rossby Centre Regional Climate Model (RCA4) driven by nine global circulation models (GCMs), to skilfully...     

The simulation of the initial mass function and star formation efficiency

The fragmentation of a molecular cloud is modelled as a random process by the Monte Carlo method. The probability of the fragmentation is a function of the cloud initial mass and decreases rapidly for mass lower than critical mass, which is a defined parameter. The modelled IMF is compared with the mean mass function in open clusters assumed here as the observed IMF. The best fit was found for initial mass 3×10³ M _s and for the critical mass range 0.4 to 0.6M _s . It also implies the star formation efficiency to be about 0.3.Paper presented at a Workshop on The Role of Dust in Dense Regions of Interstellar Matter, held at Georgenthal, G.D.R., in March 1986.     

A note on the conditions for SSD–ADAF transitions

One of the necessary matching conditions between an optically thin, hot, advectively dominated part of an accretion disc (ADAF) and the standard Shakura–Sunyaev disc (SSD) part is that the matching transition region must rotate with an orbital speed that is faster than the Keplerian one. We discuss properties of the SSD–ADAF transition in terms of a simple two-dimensional hydrodynamical model.     

Crack modelling of concrete, rock and soil with inner softening bands

To model the cracking behaviour of brittle materials, different existing methods for treating the fracture zone can be used. The inner softening band (ISB) approach belongs to those methods which introduce a displacement discontinuity in which a constitutive relationship between opening displacements and tractions is assumed. This group of methods avoids difficulties in the localization zone caused by ambiguous definitions of strain measures and fracture zone widths. Whichever method is used, it is important that the proper amount of energy is dissipated. This is achieved automatically in ISB without the introduction of any extra material parameters other than the elastic constants and those describing the softening curve. Variations in mesh sizes and arrangements have shown no great influence on the total response, and the crack pattern is a part of the solution in contrast to most other methods in which it must be presumed. The concept is simple and inner softening bands have been successfully implemented within triangular three-node elements and preliminary within six-node triangular elements. The results obtained so far from various kinds of tests have shown very good performance and further development is planned.     

Chlorine-36 and the initial value problem

 Chlorine-36 is a radionuclide with a half-life of 3.01×10⁵a. Most ³⁶Cl in the hydrosphere originates from cosmic radiation interacting with atmospheric gases. Large amounts were also produced by testing thermonuclear devices during 1952–58. Because the monovalent anion, chloride, is the most common form of chlorine found in the hydrosphere and because it is extremely mobile in aqueous systems, analyses of both total Cl^– as well as ³⁶Cl have been important in numerous hydrologic studies. In almost all applications of ³⁶Cl, a knowledge of the initial, or pre-anthropogenic, levels of ³⁶Cl is useful, as well as essential in some cases. Standard approaches to the determination of initial values have been to: (a) calculate the theoretical cosmogenic production and fallout, which varies according to latitude; (b) measure ³⁶Cl in present-day precipitation and assume that anthropogenic components can be neglected; (c) assume that shallow groundwater retains a record of the initial concentration; (d) extract ³⁶Cl from vertical depth profiles in desert soils; (e) recover ³⁶Cl from cores of glacial ice; and (f) calculate subsurface production of ³⁶Cl for water that has been isolated from the atmosphere for more than one million years. The initial value from soil profiles and ice cores is taken as the value that occurs directly below the depth of the easily defined bomb peak. All six methods have serious weaknesses. Complicating factors include ³⁶Cl concentrations not related to cosmogenic sources, changes in cosmogenic production with time, mixed sources of chloride in groundwater, melting and refreezing of water in glaciers, and seasonal groundwater recharge that does not contain average year-long concentrations of ³⁶Cl. Received, December 1996 · Revised, August 1997 · Accepted, August 1997