Comparative analysis between operational weather prediction models and QuikSCAT wind data near the Galician coast

Wind measurements from SeaWinds scatterometer on the NASA QuikSCAT satellite and wind forecasts from two different operational numerical models provided by MeteoGalicia were compared for a 4-year period (2002–2005) in Galician coast environment. Available wind data buoy measurements were also used to complement the analysis. A statistical analysis based on mean errors, root mean square errors and complex correlation was performed from spatial, temporal and directional points of view.In the spatial comparison no significant differences between models and satellite were observed and the error magnitudes of the models are compatible with typical QuikSCAT errors. The suitability of satellite wind estimations for data assimilation in these models must be further investigated. Negative bias of models with respect to the satellite was also confirmed with buoy data, in such a way that models overestimation is smaller than the satellite one. Big errors in wind direction appear in southeasterly and southwesterly winds for both satellite and models, contributing to high RMSE values when compared to buoy data. These errors were mainly attributed to the effect of insufficient spatial resolution near shore.     

Short-term post-earthquake bus transit planning in Managua

In December 1972 an earthquake hit Managua, Nicaragua, killing 5,000 inhabitants, while wounding 20,000 persons and destroying its core area of 13 square kilometers. The earthquake also seriously disrupted the bus transit system. Bus transit patronage fell as a result of the loss of population of 144,000 persons who moved temporarily out of the city, while costs rose appreciably as both round trip bus distances and the proportion of the trips on unpaved roads doubled with respect to pre-earthquake levels. By September 1973, ten of the thirteen bus companies were on the verge of bankruptcy and were demanding from the regulatory body stiff increases in fares.This paper presents analyses and recommendations for improving the short-term efficiency of bus routes in Managua by applying planning techniques suited to the data availability problems of developing countries.In view of the lack of cost data for the bus routes, a cost analysis was conducted; Jan de Weille's cost factors were adapted to Nicaragua to portray the near bankrupt condition of most routes. These cost factors were verified by means of selected interviews with the private transit entrepreneurs.Next, a simple patronage prediction model was developed which related patronage for a route to the population and employment served by the route. This simple patronage model was then applied to redesign the bus routes of Managua. A policy of bus route redesign coupled with the paving of city streets along the bus routes is shown to have sufficed in avoiding fare increases. Finally, the paper reviews the bus transit regulatory setting and develops some recommendations for its improvement.Adjunct Associate Professor of the Catholic University of America. This study was conducted while the author was stationed in Nicaragua as a consultant to Harvard Development Advisory Service.     

ICE 3的线性涡流制动--技术观点和运行经验

线性涡流制动(WB)首次正式用于德国铁路的ICE 3列车中,其优点是工作无磨损且与轮轨间的粘着系数无关.简要介绍线性涡流制动批量使用前的主要开发步骤及与线路的相互作用.     

Hydrology, sediment yield, erosion and sedimentation rates in the estuarine environment of the Ria de Vigo, Galicia, Spain

The aim of this study is to provide a budget study with calculated erosion rates. Three methods have been used to calculate sediment yield and denudation rates in the Ria de Vigo: (1) measurements of sediment loads, (2) measurements of sediment accumulation rates at the coast, (3) theoretical calculations of potential denudation. Sediment loads and water discharge were measured over a period of 14 months from May 1997 to July 1998. Two of the tributaries entering the Ria de Vigo were monitored for 12 more months, from May 2000 to May 2001, to observe changes in discharge and sediment loads. This period corresponded with atypical precipitation, with peak monthly values (600 mm) three times higher than those on record.Water rating curves are typically exponential. Suspended and dissolved loads vary for different rivers, showing values of 1.5 to 130 mg/l during 1997/1998. For 2000/2001, these values are twice as high. Suspended load versus discharge relationships for 1997/1998 were logarithmic, but data from 2000/2001 does not fit the same equation. Dissolved loads are several times higher than suspended loads in almost all cases. Dissolved load concentrations vary more widely with discharge than suspended loads. This is probably due to local pollution and contamination from marine spray in areas closer to the sea.Second, erosion rates and bed load sediment yields were calculated from accumulation rates at the Ramallosa Complex. Well-preserved estuarine and tidal sediments, associated with the Minor River, have accumulated in this area during the Holocene. ¹⁴C ages allow calculation of sedimentation rates (SR) for two intervals. The lower interval extends from 2001 to 484 years BP and yields an SR of 1.12 mm/a. The upper interval extends from 484 years BP to the present and has an SR of 3.3–4.4 mm/a. These differences may be explained by basin dynamics as the beach progressively encloses the area and also by human interference. From sedimentary facies analysis it is concluded that 90% to 95% of the accumulated deposits were transferred to the basin as bed load. Muddy deposits (mostly marshes) are better developed at the upper part of the sediment pile, and inner areas, indicating a progressive shallowing and filling up of the basin. Most of suspended load is exported to the ria, whereas the Ramallosa Complex acts as a sediment sink for bed load derived material.Calculated potential erosion rates using Ahnert's [Am. J. Sci. 268 (1970) 243] equation show lower values than those estimated from river load concentrations. Potential erosion rates for the Minor River are higher than for the Lagares River which contrast with mechanical denudation rate values from river loads during 1997/1998 which are higher for the Lagares River. During 2000/2001 MDR values were higher than those of the potential erosion rates for both rivers, in line with the extremely high precipitation. Higher values in the Lagares could be in part due to human interference.     

The vertical disintegration of ship management: choice criteria for third party selection and evaluation

An assessment of the rationale for the vertical disintegration of ship management suggests that there might be compelling economic benefits for the separation of ownership from management. In this context, as a means for developing effective marketing strategies, it is important for ship managers to know the criteria used by current and prospective clients for ship manager selection and evaluation. The aim of this paper is to empirically identify the dimensions for ship manager selection and performance evaluation and their relative importance and to discuss the implications for marketing emanating from such an assessment. The methodology adopted includes the collection of secondary and primary data, both from ship managers and their clients, using interviews and a mail survey. The results indicate the prevailing importance of certain dimensions in selection (e.g. technical ability, reputation, competency) and evaluation (responsiveness, trustworthiness, technical ability), whereas it also found that price alone is not perceived to be as important in ship manager selection. It is concluded that placing emphasis on such dimensions in the formulation of a marketing strategy will contribute towards the attraction and retention of clients, whereas cost-cutting measures to allow price reduction, as well as advertising, will be ineffective over the long term.     

Lateral Vehicle Behaviour: Comparison of Subjective/Objective Assessment Using the Choquet Integral

This paper presents an original method for the aggregation of transverse behaviour indicators obtained first from a subjective assessment then from an objective one of different vehicles tested under normal working conditions. The Choquet integral is used with respect to fuzzy measures. The main advantage of this method is to take account of the existing interactions between the indicators: redundancy, complementarity, inde-pendence. When this tool is used for subjective and objective evaluations, the computation methods of the objective indicators can be validated. Moreover, the influence of the human factor in the judgment of vehicle behaviour is easier to understand.     

Characteristics and potential impacts of under-ice river plumes in the seasonally ice-covered Bothnian Bay (Baltic Sea)

The northernmost basin of the Baltic Sea, the Bothnian Bay, is ice-covered for about half the year. During this time, distinct under-ice river plumes develop, even seaward of the smallest rivers, that are substantially thicker and larger in extent than during the summer months. Wind mixing is negligible, and during late spring in April or May, the highest annual discharge occur while the sea is ice covered, thus providing conditions for the formation of extensive under-ice plumes. These plumes are characterised by high levels of trace elements (e.g., Al, Fe and Zn), organic matter (TOC and dissolved organic carbon [DOC]), nutrients and also optically active substances (colored dissolved organic matter, CDOM). The under-ice plumes provide an important pathway for undiluted transport of land-derived substances to the pelagic waters of the basin, affecting the salinity, chemistry and optical properties of coastal waters. Freshwater ice growth on the underside of an existing sea ice sheet also restricts the buildup of sea ice and under-ice algal communities, potentially in large areas along the coasts. Plume water influences the optical characteristics of coastal waters for a period of time after ice break-up, potentially affecting primary production in these areas. Furthermore, the formation of under-ice plumes potentially has a positive feedback on the ice season length due to freshening of the coastal waters (earlier freeze-up) and restricted oceanic heat flux (slower melting).     

Resolving the impact of short-term variations in physical processes impacting on the spawning environment of eastern Baltic cod: application of a 3-D hydrodynamic model

Variations in oxygen conditions below the permanent halocline influence the ecosystem of the Baltic Sea through a number of mechanisms. In this study, we examine the effects of physical forcing on variations in the volume of deep oxygenated water suitable for reproductive success of central Baltic cod. Recent research has identified the importance of inflows of saline and oxygenated North Sea water into the Baltic Sea for the recruitment of Baltic cod. However, other processes have been suggested to modify this reproduction volume including variations in timing and volume of terrestrial runoff, variability of the solubility of oxygen due to variations in sea surface temperature as well as the influence of variations in wind stress. In order to examine the latter three mechanisms, we have performed simulations utilizing the Kiel Baltic Sea model for a period of a weak to moderate inflow of North Sea water into the Baltic, modifying wind stress, freshwater runoff and thermal inputs. The model is started from three-dimensional fields of temperature, salinity and oxygen obtained from a previous model run and forced by realistic atmospheric conditions. Results of this realistic reference run were compared to runs with modified meteorological forcing conditions and river runoff.From these simulations, it is apparent that processes other than major Baltic inflows have the potential to alter the reproduction volume of Baltic cod. Low near-surface air temperatures in the North Sea, the Skagerrak/Kattegat area and in the western Baltic influence the water mass properties (high oxygen solubility). Eastward oriented transports of these well-oxygenated highly saline water masses may have a significant positive impact on the Baltic cod reproduction volume in the Bornholm Basin.Finally, we analysed how large scale and local atmospheric forcing conditions are related to the identified major processes affecting the reproduction volume.