Meteorological and runoff time-series characteristics in a small,high-Arctic glaciated basin,Svalbard

This paper examines characteristics of meteorological and runoff time-series collected from the Brøggerbreen glacier basin, Svalbard, during 1991 and 1992. Proglacial discharge and electrical conductivity were monitored at two gauging stations: one immediately downstream of the terminus of Austre Brøggerbreen and another c. 2·5 km downstream, in order to assess the contribution of the intervening proglacial sandur. Meteorological time-series (incident radiation, wind speed and direction, air temperature and precipitation) were monitored on the proglacial sandur. Changes in wind direction, incident radiation receipt and air temperature were used as a basis for separating the time-series into different periods. These periods allowed the relative significance of advective and incident (short-wave) radiative forcing of air temperatures to be determined at diurnal and synoptic time-scales. The analysis shows that incident radiation dominated over advection in the forcing of diurnal variations in air temperature during all the periods. At the synoptic scale, both processes were periodically dominant in forcing air temperature variability. An examination of synoptic charts supports the use of ground level measurements to describe the effect of energy advection upon the synoptic air temperature variability and indicates the role of large-scale circulation patterns in the delivery of energy for ablation under different conditions. Interrelationships between the hydrological and meteorological time-series are then used to characterize the response of the glacierized part of the catchment to meteorological forcing throughout the two ablation seasons. The analyses show that the recession of the snowpack across the proglacial and glacial portions of the basin has an important effect on the catchment contributing area contributing to runoff and the lag between energy inputs and meltwater discharge outputs. © 1998 John Wiley & Sons, Ltd.     

A geophysical survey of the De Gerlache Seamounts: preliminary results

 The De Gerlache Seamounts actually consist of two medium-sized guyots, with summits at depths of 350–600 m. Acoustic profiler data show no significant sediment on these guyots. Alkaline basalts dredged from the summit of the eastern guyot yield K/Ar ages between 20.1±1.0 and 23.2±1.2 Ma. Basement ridges and sediment-filled troughs between the guyots are associated with the prominent gravity anomaly extending north from the Antarctic margin. This structure possibly played a role in the guyot formation, however, the question of how the De Gerlache Seamounts are related to this gravity anomaly remains uncertain. Received: 13 February 1997 / Revision received: 30 September 1997     

Glaciers in Svalbard: mass balance, runoff and freshwater flux

Gain or loss of the freshwater stored in Svalbard glaciers has both global implications for sea level and, on a more local scale, impacts upon the hydrology of rivers and the freshwater flux to fjords. This paper gives an overview of the potential runoff from the Svalbard glaciers. The freshwater flux from basins of different scales is quantified. In small basins (A < 10 km²), the extra runoff due to the negative mass balance of the glaciers is related to the proportion of glacier cover and can at present yield more than 20% higher runoff than if the glaciers were in equilibrium with the present climate. This does not apply generally to the ice masses of Svalbard, which are mostly much closer to being in balance. The total surface runoff from Svalbard glaciers due to melting of snow and ice is roughly 25 ± 5 km³ a⁻¹, which corresponds to a specific runoff of 680 ± 140 mm a⁻¹, only slightly more than the annual snow accumulation. Calving of icebergs from Svalbard glaciers currently contributes significantly to the freshwater flux and is estimated to be 4 ± 1 km³ a⁻¹ or about 110 mm a⁻¹.     

Optimum operation of restoration techniques for eutrophic water bodies

Operating rules have been applied in water resources management for a long time in order to control and supply a requiredquantity (volume) of water. The operating rules have to guarantee the optimum management of the reservoir(s). Thequality of the stored water has been satisfactory for the desired utilization up to the sixties. Due to the deterioration of reservoir water quality through human impacts, however, increased attention had to be paid since. Eutrophication of stagnant waters is still an unsolved problem. Through means of various restoration techniques, i.e., dilution/flushing or hypolimnetic withdrawal, the quality of the stored water can be improved. Continuous operation or appropriate time or depth variant operating rules are required to achieve this goal. The paper presents such rules for long-term operation. They have been established for the first time and can he represented in two or three-dimensional graphs depending on the number of included components (e.g., actual water storage and quality). The quality operating rules take into account the dynamics of the processes in aquatic ecosystems. Simplifications with regard to application and acceptance (e.g., clarity) are developed and tested. The general validity and efficiency of the operating rules have been proved in a case study (a multi-purpose reservoir) and a fictitious lake.     

Adaptive Zoning for Transport Mode Choice Modeling

Adaptive zoning is a recently introduced method for improving computer modeling of spatial interactions and movements in the transport network. Unlike traditional zoning, where geographic locations are defined by one single universal plan of discrete land parcels or ‘zones’ for the study area, adaptive zoning establishes a compendium of different zone plans, each of which is applicable to one journey origin or destination only. These adaptive zone plans are structured to represent strong spatial interactions in proportionately more detail than weaker ones. In recent articles, it has been shown that adaptive zoning improves, by a large margin, the scalability of models of spatial interaction and road traffic assignment. This article confronts the method of adaptive zoning with an application of the scale and complexity for which it was intended, namely an application of mode choice modeling that at the same time requires a large study area and a fine‐grained zone system. Our hypothesis is that adaptive zoning can significantly improve the accuracy of mode choice modeling because of its enhanced sensitivity to the geographic patterns and scales of spatial interaction. We test the hypothesis by investigating the performance of three alternative models: (1) a spatially highly detailed model that is permissible to the maximum extent by available data, but requires a high computational load that is generally out of reach for rapid turnaround of policy studies; (2) a mode choice model for the same area, but reducing the computational load by 90% by using a traditional zone system consisting of fewer zones; and (3) a mode choice model that also reduces the computational load by 90%, but based on adaptive zoning instead. The tests are carried out on the basis of a case study that uses the dataset from the London Area Transport Survey. Using the first model as a benchmark, it is found that for a given computational load, the model based on adaptive zoning contains about twice the amount of information of the traditional model, and model parameters on adaptive zoning principles are more accurate by a factor of six to eight. The findings suggest that adaptive zoning has a significant potential in enhancing the accuracy of mode choice modeling at the city or city‐region scale.     

Tensor visualizations in computational geomechanics

We present a novel technique for visualizing tensors in three dimensional (3D) space. Of particular interest is the visualization of stress tensors resulting from 3D numerical simulations in computational geomechanics. To this end we present three different approaches to visualizing tensors in 3D space, namely hedgehogs, hyperstreamlines and hyperstreamsurfaces. We also present a number of examples related to stress distributions in 3D solids subjected to single and load couples. In addition, we present stress visualizations resulting from single‐pile and pile‐group computations. The main objective of this work is to investigate various techniques for visualizing general Cartesian tensors of rank 2 and it's application to geomechanics problems. Copyright © 2002 John Wiley & Sons, Ltd.     

Regression models for daily stream temperature simulation: case studies for the river Elbe,Germany

Daily stream temperatures are needed in a number of analyses. Such analyses might focus on aquatic organisms or industrial activities. To protect aquatic systems, industrial activities, for example, water withdrawals or discharges, are sometimes restricted. To evaluate where new industrial settings should be placed or if climate change will affect already existing industrial settings, the simulation of stream temperature is needed. Stream temperature models with weekly or monthly time scale might not be sufficient for this kind of analysis. Different regression models to simulate daily stream temperature for the river Elbe (Germany) are developed and their performance is estimated. For the calibration period the Nash–Sutcliffe coefficient (NSC) for the simplest model is 0·97, and the root mean squared error (RMSE) is 1·48 °C. For the most sophisticated model the NSC also is 0·97. However, the RMSE is 1·32 °C. For the validation period the NSC for the simplest model is 0·96, and the RMSE is 1·45 °C. The NSC for the most sophisticated model is 0·97, and the RMSE is 1·25 °C. Copyright © 2010 John Wiley & Sons, Ltd.     

Monitoring of Mesoscale Precipitation Systems in the Alps and the Northern Alpine Foreland by Radar and Rain Gauges

Summary.  Mesoscale convective precipitation systems in the Alpine region are studied by analyzing radar and rain gauge data. The data from weather radars in Austria, France, Germany, and Switzerland are combined into a composite. Availability of radar data restricts the study mainly to the northern part of the Alpine region. Mesoscale convective systems (MCS) occur often in this region and are comparable to large systems observed in the USA. Seven precipitation events lasting one to six days from the years 1992–1996 are examined in detail. They all moved west to east and showed no diurnal preference in formation or dissipation. They reach sizes of 2 − 6 · 10⁴ km². MCS with leading-line trailing-stratiform structure tended to be larger and more intense. A 25-year set of rain gauge data indicates that a giant MCS (covering more than 4 · 10⁴ km² with more than 30 mm/day) occurs every 6 years in the northern Alpine region. MCS occur more frequently in the southern Alpine region. Received February 25, 1999/Revised June 29, 1999