Staff Publications

Staff Publications

  • external user (warningwarning)
  • Log in as
  • language uk
  • About

    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

    We have a manual that explains all the features 

    Current refinement(s):

    Records 1 - 20 / 69

    • help
    • print

      Print search results

    • export

      Export search results

    Check title to add to marked list
    West Nile Virus: High Transmission Rate in North-Western European Mosquitoes Indicates Its Epidemic Potential and Warrants Increased Surveillance
    Fros, J.J. ; Geertsema, C. ; Vogels, C.B.F. ; Roosjen, P.P.J. ; Failloux, A.B. ; Vlak, J.M. ; Koenraadt, C.J.M. ; Takken, W. ; Pijlman, G.P. - \ 2015
    PLoS Neglected Tropical Diseases 9 (2015)7. - ISSN 1935-2727
    united-states - differential virulence - experimental-infection - vector competence - lineage 1 - outbreak - circulation - strains - disease - encephalitis
    West Nile virus (WNV) is on the rise in Europe, with increasing numbers of human cases of neurological disease and death since 2010. However, it is currently unknown whether or not WNV will continue to spread to north-western Europe (NWE), in a fashion similar to the WNV epidemic sweep in the United States (1999–2004). The presence of competent mosquitoes is a strict requirement for WNV transmission, but no laboratory studies have been conducted with the new European lineage 2 WNV outbreak strain. Our study is the first to investigate transmissibility in NWE Culex pipiens for lineage 2 WNV in a systematic, direct comparison with North American Culex pipiens and with the lineage 1 WNV strain. We demonstrate that European mosquitoes are highly competent for both WNV lineages, which underscores the epidemic potential ofWNV in Europe. However, the transmission rate for lineage 2 WNV was significantly lower in North American mosquitoes, which indicates different risk levels between both continents for lineage 2 but not lineage 1 WNV. Based on our result, we propose that WNV surveillance in mosquitoes and birds must be intensified in Europe to allow early detection, timely intervention strategies and prevent outbreaks of WNV neurological disease.
    Exploring the efficiency of bias corrections of regional climate model output for the assessment of future crop yields in Europe
    Bakker, A.M.R. ; Bessembinder, J.J.E. ; Wit, A.J.W. de; Hurk, B.J.J.M. van den; Hoek, S.B. - \ 2014
    Regional Environmental Change 14 (2014)3. - ISSN 1436-3798 - p. 865 - 877.
    weather generator - global radiation - change scenarios - era-interim - variability - precipitation - projections - simulation - uncertainty - circulation
    Excessive summer drying and reduced growing season length are expected to reduce European crop yields in future. This may be partly compensated by adapted crop management, increased CO2 concentration and technological development. For food security, changes in regional to continental crop yield variability may be more important than changes in mean yields. The assessment of changes in regional and larger scale crop variability requires high resolution and spatially consistent future weather, matching a specific climate scenario. Such data could be derived from regional climate models (RCMs), which provide changes in weather patterns. In general, RCM output is heavily biased with respect to observations. Due to the strong nonlinear relation between meteorological input and crop yields, the application of this biased output may result in large biases in the simulated crop yield changes. The use of RCM output only makes sense after sufficient bias correction. This study explores how RCM output can be bias corrected for the assessment of changes in European and subregional scale crop yield variability due to climate change. For this, output of the RCM RACMO of the Royal Netherlands Meteorological Institute was bias corrected and applied within the crop simulation model WOrld FOod STudies to simulate potential and water limited yields of three divergent crops: winter wheat, maize and sugar beets. The bias correction appeared necessary to successfully reproduce the mean yields as simulated with observational data. It also substantially improved the year-to-year variability of seasonal precipitation and radiation within RACMO, but some bias in the interannual variability remained. This is caused by the fact that the applied correction focuses on mean and daily variability. The interannual variability of growing season length, and as a consequence the potential yields too, appeared even deteriorated. Projected decrease in mean crop yields is well in line with earlier studies. No significant change in crop yield variability was found. Yet, only one RCM is analysed in this study, and it is recommended to extend this study with more climate models and a slightly adjusted bias correction taking into account the variability of larger time scales as well
    Multiyear predictability of the North Atlantic subpolar gyre
    Wouters, B. ; Hazeleger, W. ; Drijfhout, S. ; Oldenborgh, G.J. van; Guemas, V. - \ 2013
    Geophysical Research Letters 40 (2013)12. - ISSN 0094-8276 - p. 3080 - 3084.
    surface-temperature - variability - circulation - prediction - ensemble - model
    [1] In decadal predictability studies, the subpolar Atlantic stands out as a region of high potential and real predictability. Since local temperature and salinity variations in the region are for a large part controlled by ocean dynamics, skillful predictability of the local ocean dynamics is a prerequisite to obtain multiyear predictability of other variables such as sea surface temperature. In this study, we discuss the predictability of the main ocean current system in the region, the subpolar gyre. From perfect model hindcasts exploiting initial condition information only from realistic ocean observation locations, we find that predictability is increased when Argo subsurface data are included. In our real-world experiments with initialized hindcasts, the observed decline in subpolar gyre strength of the mid-1990s is reproduced well and we find predictability of the subpolar gyre up to 2 years ahead, comparable to the skill of a damped persistence model.
    Likely Ranges of Climate Change in Bolivia
    Seiler, C. ; Hutjes, R.W.A. ; Kabat, P. - \ 2013
    Journal of Applied Meteorology and Climatology 52 (2013)6. - ISSN 1558-8424 - p. 1303 - 1317.
    south-america - change scenarios - altiplano - rainfall - models - andes - variability - circulation - amazon - trends
    Bolivia is facing numerous climate-related threats, ranging from water scarcity due to rapidly retreating glaciers in the Andes to a partial loss of the Amazon forest in the lowlands. To assess what changes in climate may be expected in the future, 35 global circulation models (GCMs) from the third and fifth phases of the Coupled Model Intercomparison Project (CMIP3/5) were analyzed for the Bolivian case. GCMs were validated against observed surface air temperature, precipitation, and incoming shortwave (SW) radiation for the period 1961–90. Weighted ensembles were developed, and climate change projections for five emission scenarios were assessed for 2070–99. GCMs revealed an overall cold, wet, and positive-SW-radiation bias and showed no substantial improvement from the CMIP3 to the CMIP5 ensemble for the Bolivian case. Models projected an increase in temperature (2.5°–5.9°C) and SW radiation (1%–5%), with seasonal and regional differences. In the lowlands, changes in annual rainfall remained uncertain for CMIP3 whereas CMIP5 GCMs were more inclined to project decreases (-9%). This pattern also applied to most of the Amazon basin, suggesting a higher risk of partial biomass loss for the CMIP5 ensemble. Both ensembles agreed on less rainfall (-19%) during drier months (June–August and September–November), with significant changes in interannual rainfall variability, but disagreed on changes during wetter months (January–March). In the Andes, CMIP3 GCMs tended toward less rainfall (-9%) whereas CMIP5 tended toward more (+20%) rainfall during parts of the wet season. The findings presented here may provide inputs for studies of climate change impact that assess how resilient human and natural systems are under different climate change scenarios.
    Climate Variability and Trends in Bolivia
    Seiler, C. ; Hutjes, R.W.A. ; Kabat, P. - \ 2013
    Journal of Applied Meteorology and Climatology 52 (2013)1. - ISSN 1558-8424 - p. 130 - 146.
    amazon basin - interdecadal variability - tropical pacific - rainfall - circulation - oscillation - altiplano - andes - enso - ocean
    Climate-related disasters in Bolivia are frequent, severe, and manifold and affect large parts of the population, economy, and ecosystems. Potentially amplified through climate change, natural hazards are of growing concern. To better understand these events, homogenized daily observations of temperature (29 stations) and precipitation (68 stations) from 1960 to 2009 were analyzed in this study. The impact of the positive (+) and negative (-) phases of the three climate modes (i) Pacific decadal oscillation (PDO), (ii) El Niño–Southern Oscillation (ENSO) with El Niño (EN) and La Niña (LN) events, and (iii) Antarctic Oscillation (AAO) were assessed. Temperatures were found to be higher during PDO(+), EN, and AAO(+) in the Andes. Total amounts of rainfall, as well as the number of extreme events, were higher during PDO(+), EN, and LN in the lowlands. During austral summer [December–February (DJF)], EN led to drier conditions in the Andes with more variable precipitation. Temperatures increased at a rate of 0.1°C per decade, with stronger increases in the Andes and in the dry season. Rainfall totals increased from 1965 to 1984 [12% in DJF and 18% in June–August (JJA)] and decreased afterward (-4% in DJF and -10% in JJA), following roughly the pattern of PDO. Trends of climate extremes generally corresponded to trends of climate means. Findings suggest that Bolivia’s climate will be warmer and drier than average in the near-term future. Having entered PDO(-) in 2007, droughts and LN-related floods can be expected in the lowlands, while increasing temperatures suggest higher risks of drought in the Andes.
    The rise and fall for the NE Atlantic blue whiting (Micromesistus Poutassou)
    Payne, M.R. ; Egan, A.R. ; Fassler, S.M.M. ; Hatun, H. ; Holst, J.C. ; Jacobsen, J.A. - \ 2012
    Marine Biology Research 8 (2012)5-6. - ISSN 1745-1000 - p. 475 - 487.
    eastern north-atlantic - haddock melanogrammus-aeglefinus - subpolar gyre - larval fish - scomber-scombrus - egg size - recruitment - growth - stock - circulation
    The Northeast Atlantic blue whiting (Micromesistius poutassou) stock has undergone striking changes in abundance in the last 15 years. The stock increased dramatically in the late 1990s due to a succession of eight unusually strong year classes and dropped again equally dramatically after 2005 when the recruitment collapsed to former levels. The North Atlantic subpolar gyre has previously been shown to have a strong influence on the behaviour of this stock: synchronous changes in the gyre and recruitment suggest a causal linkage and the possibility of forecasting recruitment. A range of mechanisms are reviewed that may explain these observed changes, with two major candidate hypotheses being identified. One hypothesis suggests that the large mackerel (Scomber scombrus) stock in this region may feed on the pre-recruits of blue whiting, with the spatial overlap between blue whiting and mackerel being regulated by the subpolar gyre. Alternatively, variations in the physical environment may have given rise to changes in the amount, type and availability of food for larvae and juveniles, impacting their growth and survival and therefore recruitment. It was not possible to draw firm conclusions about the validity of either of these hypotheses: nevertheless, forecasting recruitment to this stock may be possible in the future if the underlying mechanisms can be resolved.
    EC-Earth V2.2: description and validation of a new seamless earth system prediction model
    Hazeleger, W. ; Wang, X. ; Severijns, C. ; Linden, E.C. van der - \ 2012
    Climate Dynamics 39 (2012)11. - ISSN 0930-7575 - p. 2611 - 2629.
    sea-surface temperature - climate-change - energy budget - coupled models - ecmwf model - ocean - variability - ice - simulations - circulation
    EC-Earth, a new Earth system model based on the operational seasonal forecast system of the European Centre for Medium-Range Weather Forecasts (ECMWF), is presented. The performance of version 2.2 (V2.2) of the model is compared to observations, reanalysis data and other coupled atmosphere–ocean-sea ice models. The largescale physical characteristics of the atmosphere, ocean and sea ice are well simulated. When compared to other coupled models with similar complexity, the model performs well in simulating tropospheric fields and dynamic variables, and performs less in simulating surface temperature and fluxes. The surface temperatures are too cold, with the exception of the Southern Ocean region and parts of the Northern Hemisphere extratropics. The main patterns of interannual climate variability are well represented. Experiments with enhanced CO2 concentrations show well-known responses of Arctic amplification, land-sea contrasts, tropospheric warming and stratospheric cooling. The global climate sensitivity of the current version of EC-Earth is slightly less than 1 K/(W m-2). An intensification of the hydrological cycle is found and strong regional changes in precipitation, affecting monsoon characteristics. The results show that a coupled model based on an operational seasonal prediction system can be used for climate studies, supporting emerging seamless prediction strategies.
    Preliminary results of a finite-element, multi-scale model of the Mahakam Delta (Indonesia)
    Brye, B. de; Schellen, S. ; Sassi, M.G. ; Vermeulen, B. ; Karna, T. ; Deleersnijder, E. ; Hoitink, A.J.F. - \ 2011
    Ocean Dynamics 61 (2011)8. - ISSN 1616-7341 - p. 1107 - 1120.
    mesh generation - makassar strait - circulation - estuary - ocean - river - rofi - sea
    The Mahakam is a 980-km-long tropical river flowing in the East Kalimantan province (Borneo Island, Indonesia). A significant fraction of this river is influenced by tides, the modelling of which is the main subject of this study. Various physical and numerical issues must be addressed. In the upstream part of the domain, the river flows through a region of three lakes surrounded by peat swamps. In the lowland regions, the river is meandering and its hydrodynamics is mostly influenced by tides. The latter propagate upstream of the delta, in the main river and its tributaries. Finally, the mouth of the Mahakam is a delta exhibiting a high number of channels connected to the Makassar Strait. This article focusses on the flow in the delta channels, which is characterised by a wide range of time and space scales. To capture most of them, the depth-integrated and the section-integrated versions of the unstructured mesh, finite-element model Second-Generation Louvain-la-Neuve Ice-Ocean Model are used. Unstructured grids allow for a refinement of the mesh in the narrowest channels and also an extension of the domain upstream and downstream of the delta in order to prescribe the open-boundary conditions. The Makassar Strait, the Mahakam Delta and the three lakes are modelled with 2D elements. The rivers, from the upstream limit of the delta to the lakes and the upstream limit of the domain, are modelled in 1D. The calibration of the tidal elevation simulated in the Mahakam Delta is presented. Preliminary results on the division of the Eulerian residual discharge through the channels of the delta are also presented. Finally, as a first-order description of the long-term transport, the age of the water originating from the upstream limit of the delta is computed. It is seen that for May and June 2008, the time taken by the water parcel to cross the estuary varies from 4 to 7 days depending on the channel under consideration.
    Tidal and subtidal flow patterns o a tropical continental shelf semi-insulated by coral reefs
    Tarya, A. ; Hoitink, A.J.F. ; Vegt, M. van der - \ 2010
    Journal of Geophysical Research: Oceans 115 (2010). - ISSN 2169-9275 - 16 p.
    great barrier-reef - residual currents - barotropic tides - transport - model - ocean - sea - circulation - sediment - strait
    The present study sets out to describe the tidal and subtidal water motion at the Berau coastal shelf, which represents a tropical continental shelf area of variable width hosting a complex of barrier reefs along its oceanic edge. Moored and shipboard measurements on currents and turbulence were made as part of the multidisciplinary East Kalimantan Research Program. These results and collected data on sea levels, meteorology and bathymetry, were used to setup and calibrate a three-dimensional barotropic hydrodynamic model in the ECOMSED environment, which is derived from the Princeton Ocean Model. Concurrent profile measurements of flow velocity and Reynolds stress with an acoustic Doppler current profiler were used to infer values of the drag coefficient on locations on the shelf and within the barrier reef environment. The drag coefficients determined from shelf measurements differed less than 20% from optimal model settings. Diurnal and semidiurnal tides have the same character, propagating across the isobaths with amplitudes that increase toward the coast. The tidal amplification is captured in a one-dimensional model, revealing an analogy with the Amazon Shelf. Regarding the subtidal depth-mean flow, tidal Eulerian residual currents dominate over monsoon-driven currents. Lagrangian mean flows reveal freshwater pathways from the coast to the coral reef environment. At a regional scale, the reef complex is established to be semitransparent to tides. The barrier reef influences the tidal phases rather than the amplitudes, especially in the shelf region that is fringed by the reefs. This may explain why tidal phases predicted from hydrodynamic models of tropical continental shelves often feature substantial discrepancies from observations.
    State-of-the-Art 2009 : Circulatienorm bij tulp
    Wildschut, J. ; Kok, M. - \ 2010
    omloop - lucht - luchtkwaliteit - luchtstroming - luchtdroging - bloembollen - tulpen - opslag - circulation - air - air quality - air flow - air drying - ornamental bulbs - tulips - storage
    Poster over circulatienorm bij tulp. Geconcludeerd wordt dat om temperatuurs- en RV-verschillen tussen kisten te minimaliseren is een veel lagere circulatienorm voldoende.
    De emissie-arme kas kan niet wachten
    Beerling, E.A.M. - \ 2010
    Groenten en Fruit Magazine 2010 (2010)9. - ISSN 1879-7318 - p. 46 - 47.
    emissie - beperking - oppervlaktewater - reductie - afvalwaterbehandeling - omloop - cultuur zonder grond - glastuinbouw - emission - restraint - surface water - reduction - waste water treatment - circulation - soilless culture - greenhouse horticulture
    We kunnen er niet meer omheen: de glastuinbouw is medeverantwoordelijk voor te hoge emissies naar het oppervlaktewater. Elke teler zal zijn bedrijf kritisch onder de loep moeten nemen. De keuze is: de emissie drastische verlagen of eerdaags middelen kwijt raken.
    Hydrologic impacts of climate change on the Nile River basin: Implications of the 2007 IPCC climate scenarios
    Beyene, T. ; Lettenmaier, D.P. ; Kabat, P. - \ 2010
    Climatic Change 100 (2010)3-4. - ISSN 0165-0009 - p. 433 - 461.
    water-resources - united-states - model - precipitation - temperature - simulation - variability - circulation - responses - ethiopia
    We assess the potential impacts of climate change on the hydrology and water resources of the Nile River basin using a macroscale hydrology model. Model inputs are bias corrected and spatially downscaled 21st Century simulations from 11 General Circulation Models (GCMs) and two global emissions scenarios (A2 and B1) archived from the 2007 IPCC Fourth Assessment Report (AR4). While all GCMs agree with respect to the direction of 21st Century temperature changes, there is considerable variability in the magnitude, direction, and seasonality of projected precipitation changes. Our simulations show that, averaged over all 11 GCMs, the Nile River is expected to experience increase in streamflow early in the study period (2010–2039), due to generally increased precipitation. Streamflow is expected to decline during mid- (2040–2069) and late (2070–2099) century as a result of both precipitation declines and increased evaporative demand. The predicted multimodel average streamflow at High Aswan Dam (HAD) as a percentage of historical (1950–1999) annual average are 111 (114), 92 (93) and 84 (87) for A2 (B1) global emissions scenarios. Implications of these streamflow changes on the water resources of the Nile River basin were analyzed by quantifying the annual hydropower production and irrigation water release at HAD. The long-term HAD release for irrigation increases early in the century to 106 (109)% of historical, and then decreases to 87 (89) and 86 (84)% of historical in Periods II and III, respectively, for the A2 (B1) global emissions scenarios. Egypt’s hydropower production from HAD will be above the mean annual average historical value of about 10,000 GWH for the early part of 21st century, and thereafter will generally follow the streamflow trend, however with large variability among GCMs. Agricultural water supplies will be negatively impacted, especially in the second half of the century
    Spatial patterns of infauna, epifauna and demersal fish communities in the North Sea.
    Reiss, H. ; Degraer, S. ; Duineveld, G.C.A. ; Craeymeersch, J.A.M. - \ 2010
    ICES Journal of Marine Science 67 (2010). - ISSN 1054-3139 - p. 278 - 293.
    species-diversity - sampling effort - irish sea - classification - circulation - model - assemblages - density - biodiversity - verification
    Understanding the structure and interrelationships of North Sea benthic invertebrate and fish communities and their underlying environmental drivers is an important prerequisite for conservation and spatial ecosystem management on scales relevant to ecological processes. Datasets of North Sea infauna, epifauna, and demersal fish (1999–2002) were compiled and analysed to (i) identify and compare spatial patterns in community structure, and (ii) relate these to environmental variables. The multivariate analyses revealed significantly similar large-scale patterns in all three components with major distinctions between a southern community (Oyster Ground and German Bight), an eastern Channel and southern coastal community, and at least one northern community (>50 m deep). In contrast, species diversity patterns differed between the components with a diversity gradient for infauna and epifauna decreasing from north to south, and diversity hotspots of demersal fish, e.g. near the major inflows of Atlantic water. The large-scale hydrodynamic variables were the main drivers for the structuring of communities, whereas sediment characteristics appeared to be less influential, even for the infauna communities. The delineation of ecologically meaningful ecosystem management units in the North Sea might be based on the structure of the main faunal ecosystem components
    Deliverable 2 (SustainAQ)
    Schneider, O. ; Julian, B. ; Bosman, R. ; Eding, E. - \ 2009
    Yerseke : IMARES (Report / Wageningen IMARES no. C054/09) - 100
    aquacultuur - viskwekerijen - visproductie - duurzaamheid (sustainability) - teeltsystemen - kennisoverdracht - centraal-europa - duurzame ontwikkeling - omloop - hergebruik van water - afvalwater - aquaculture - fish farms - fish production - sustainability - cropping systems - knowledge transfer - central europe - sustainable development - circulation - water reuse - waste water
    The European Project SustainAQ (Framework 6) aims to identify the limiting factors for the sustainable production of aquatic origin food in Eastern Europe. It focuses on the possible use of Recirculation Aquaculture Systems (RAS) as sustainable method for the production of aquatic animals as mentioned in the communication of the European Commission on Aquaculture in 2009. RASs already exist mainly in western countries and proved economically feasible. RASs allow controlling the production process including effluents, biosecurity and escapes. Eastern European countries are facing challenges related to their excessive water use waste emission, and others. Therefore, these countries are potential beneficiaries of improved sustainability through RAS use. This project intends to assess the benefits of introducing and applying RAS for Eastern European aquaculture. This project involves three Western European countries (Norway, the Netherlands and France) and six East European countries (Croatia, Turkey, Romania, Hungary, Czech Republic and Poland). Ten research institutions collaborate in different tasks (coordination, data collection, data analysis, etc.), and nine small-medium enterprises (SME) participate in data mining (Table 1). The present data is therefore based on the situation in those countries during 2006 till 2008 before the report got finally compiled in 2008/2009.
    Kasza: Design of a closed water system for the greenhouse horticulture
    Velde, R.T. van der; Voogt, W. ; Pickhardt, P.W. - \ 2008
    Water Science and Technology 58 (2008)3. - ISSN 0273-1223 - p. 713 - 725.
    tuinbouw - irrigatie - irrigatiewater - watersystemen - gesloten systemen - omloop - omgekeerde osmose - oxidatie - ontzilting - hergebruik van water - ultraviolette straling - glastuinbouw - uv-lampen - horticulture - irrigation - irrigation water - water systems - closed systems - circulation - reverse osmosis - oxidation - desalination - water reuse - ultraviolet radiation - greenhouse horticulture - uv lamps
    The need for a closed and sustainable water system in greenhouse areas is stimulated by the implementation in the Netherlands of the European Framework Directive. The Dutch national project Kasza: Design of a Closed Water System for the Greenhouse Horticulture will provide information how the water system in a greenhouse horticulture area can be closed. In this paper the conceptual design of two systems to close the water cycle in a greenhouse area is described. The first system with reverse osmosis system can be used in areas where desalination is required in order to be able to use the recycle water for irrigation of all crops. The second system with advanced oxidation using UV and peroxide can be applied in areas with more salt tolerant crops and good (low sodium) water sources for irrigation. Both systems are financially feasible in new greenhouse areas with substantial available recycle water.
    Density of pack-ice seals and penguins in the western Weddell Sea in relation to ice thickness and ocean depth
    Florentino De Souza Silva, A.P. ; Haas, C. ; Franeker, J.A. van; Meesters, H.W.G. - \ 2008
    Deep-Sea Research. Part II, tropical studies in oceanography 55 (2008)8-9. - ISSN 0967-0645 - p. 1068 - 1074.
    crab-eater seals - east antarctica - lobodon-carcinophaga - seasonal change - top predators - circulation - abundance - populations - indicators - patterns
    Aerial band transect censuses were carried out parallel with ice thickness profiling surveys in the pack ice of the western Weddell Sea during the ISPOL (Ice Station POLarstern) expedition of R.V. Polarstern from November 2004 to January 2005. Three regions were surveyed: the deep sea of the Weddell Sea, a western continental shelf/slope region where R.V. Polarstern passively drifted with an ice floe (ISPOL), and a northern region (N). Animal densities were compared among regions and in relation to bathymetry and ice thickness distribution. Crabeater seals Lobodon carcinophaga were the most abundant species in all three regions. Their density was significantly lower in the deep sea (0.50 km(-2)) than in the ISPOL (1.00 km(-2)) and northern regions (1.21 km(-2)). Weddell seals Leptonychotes weddellii were not sighted in the deep-sea region, their density elsewhere ranging from 0.03 (N) to 0.08 km(-2) (ISPOL). Leopard seals Hydrurga leptonyx were observed in all three areas, but could only be quantified in the deep-sea (0.05 km(-2)) and northern regions (0.06 km(-2)). The abundance of emperor penguins Aptenodytes forsteri was markedly higher in the northern (0.75 km(-2)) than in the ISPOL (0.13 km(-2)) and the deep-sea region (not quantified). Crabeater seal density was significantly related to ocean depth and modal ice thickness. (C) 2008 Elsevier Ltd. All rights reserved.
    Rebuilding the eastern Baltic cod stock under environmental change- a preliminary approach using stock, environmental, and management constraints
    Roeckmann, C. ; Schneider, U.A. ; St. John, M.A. ; Tol,, R.S.J. - \ 2007
    Natural Resource Modeling 20 (2007)2. - ISSN 0890-8575 - p. 223 - 262.
    gadus-morhua - recruitment models - marine reserve - sea - climate - survival - water - temperature - circulation - migration
    The population dynamics of the Eastern Baltic cod (Gadus morhua callarias L.), unlike many other stocks, shows a strong dependency on environmental conditions. To test the implications of different management policies on the stock and the fishery in a system of global environmental change, we apply a spatially disaggregated, discrete time, age-structured model of the Eastern Baltic cod stock in 50 year simulation analyses. The simulation provides an analysis of stock, yield, and revenue development under various management policies and environmental scenarios. The policy analysis, focusing on different regulations of fishing mortality, is embedded into three environmental scenarios, assuming low, medium, or high climate and environmental change. The environmental assumptions are based on simulation results from a coupled atmosphere-ocean regional climate model, which project salinity in the Baltic Sea to decrease by 7-47% in the period 2071-2100 relative to the reference period 1961-1990. Our simulation results show that a significant reduction in fishing mortality is necessary for achieving high long-term economic yields. Moreover, under the presented environmental scenarios, a stock collapse cannot be prevented. It can, however, be postponed by the establishment of a marine reserve in ICES subdivision 25.
    Eindrapportage ‘Verminderde Circulatie’ : demonstratie en optimalisering van aan/uit-regeling en frequentieregeling bij luchtcirculatie in palletkisten
    PPO Bomen-bollen, - \ 2005
    Lisse : DLV adviesgroep - 18
    bloembollen - opslagloodsen - opslag met klimaatbeheersing - ventilatoren - blazers - regelaars - vergelijkend onderzoek - omloop - ornamental bulbs - stores - controlled atmosphere stores - ventilators - blowers - controllers - comparative research - circulation
    Het project ‘Verminderde circulatie’ had tot doel om meer inzicht te krijgen in de juiste instellingen van frequentie regelaars en aan/uit-regelingen van systeem ventilatoren ten behoeve van de circulatie in bloem bollenbewaarruimten .
    Diurnal and inter-monthly variation of land surface heat fluxes over the central Tibetan Plateau area
    Ma, Y.M. ; Fan, S. ; Ishikawa, H. ; Tsukamoto, O. ; Yao, T. ; Koike, T. ; Zuo, H. ; Hu, Z. ; Su, Z. - \ 2005
    Theoretical and Applied Climatology 80 (2005)39540. - ISSN 0177-798X - p. 259 - 273.
    heterogeneous landscape - energy-balance - net-radiation - vegetation - circulation - emissivity - parameters - canopy - winter - avhrr
    The energy and water cycle over the Tibetan Plateau play an important role in the Asian monsoon system, which in turn is a major component of both the energy and water cycles of the global climate system. Using field observational data observed from the GAME/Tibet (GEWEX (Global Energy and Water cycle Experiment) Asian Monsoon Experiment on the Tibetan Plateau) and the CAMP/Tibet (CEOP (Coordinated Enhanced Observing Period) Asia-Australia Monsoon Project (CAMP) on the Tibetan Plateau), some results on the local surface energy partitioning (diurnal variation, inter-monthly variation and vertical variation etc.) are presented in this study. The study on the regional surface energy partitioning is of paramount importance over heterogeneous landscape of the Tibetan Plateau and it is also one of the main scientific objectives of the GAME/Tibet and the CAMP/Tibet. Therefore, the regional distributions and their inter-monthly variations of surface heat fluxes (net radiation flux, soil heat flux, sensible heat flux and latent heat flux) are also derived by combining NOAA-14/AVHRR data with field observations. The derived results were validated by using the ground truth, and it shows that the derived regional distributions and their inter-monthly variations of land surface heat fluxes are reasonable by using the method proposed in this study. Further improvement of the method and its applying field were also discussed.
    Luchtcirculatie, kasklimaat en productie: Deel rapportage maart-oktober 2004
    Gelder, A. de; Campen, J.B. ; Stanghellini, C. - \ 2004
    Naaldwijk : Praktijkonderzoek Plant en Omgeving B.V. Glastuinbouw (PPO 416116052) - 28
    kastechniek - luchttemperatuur - omloop - binnenklimaat - gewasproductie - teelt onder bescherming - greenhouse technology - air temperature - circulation - indoor climate - crop production - protected cultivation
    In kassen treedt veel luchtbeweging op. De invloed van geforceerde luchtbeweging in de kas ten gevolge van verwarming en/of ventilatoren in combinatie met luchtverdeelsystemen op de ruimtelijke klimaatverdeling en de daaraan gekoppelde fysische en fysiologische processen in het gewas zijn vrijwel onbekend. Uit het onderzoek met een gesloten kas (Schoonderbeek et al. 2003) kwam naar voren dat de geforceerde luchtbeweging een belangrijke verandering in het kasklimaat rond de plant tot gevolg had. De veronderstelling is dat deze verandering heeft bijgedragen aan de, in dat onderzoek gevonden, meerproductie en de behaalde energie-efficiëntie. Naar aanleiding van de resultaten van het gesloten kas experiment is door de LTO commissie tomaat gevraagd om nader onderzoek naar de oorzaken van de productieverhoging ten opzichte van de verhoging die op basis van simulatiemodellen werd verwacht. In de huidige gewasgroeimodellen is een vaste waarde aangenomen voor de grenslaagweerstand. Bij teeltsystemen, waarin luchtbeweging door geforceerde ventilatie of door beweging van planten optreedt, zal deze weerstand veranderen. Door verlaging van de weerstand kan als gevolg van een hogere CO2 uitwisseling de maximale fotosynthese toenemen. Een verlaging van de weerstand kan de transpiratie doen toenemen. Verder heeft geforceerde luchtbeweging invloed op de ruimtelijke klimaatverdeling voor temperatuur en vochtigheid. De verschillen in absolute luchtvochtigheid worden onder normale condities gering verondersteld. Een nadere analyse van het microklimaat, voor CO2 en vochtuitwisseling en de ruimtelijke verdeling bij geforceerde luchtbeweging en de daaraan gekoppelde gewasreacties geeft inzicht in de onderliggende mechanismen voor productieverbetering. Het onderzoek richt zich op de korte termijn effecten van luchtcirculatie. Benutting van deze kennis bij de keuze en besturing van de klimaatinstallaties in normale en (semi) gesloten kassen biedt uitstekende mogelijkheden om op energie-efficiënte wijze meerproductie te verkrijgen.
    Check title to add to marked list
    << previous | next >>

    Show 20 50 100 records per page

     
    Please log in to use this service. Login as Wageningen University & Research user or guest user in upper right hand corner of this page.