Staff Publications

Staff Publications

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    '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.

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Evaluating the SandFlow, an acoustic sediment transport sensor
Rezaei, Mahrooz ; Goossens, Dirk ; Riksen, Michel J.P.M. - \ 2020
Aeolian Research 42 (2020). - ISSN 1875-9637
Acoustic sensor - Sand transport - SandFlow - Wind

The SandFlow is an acoustic device for detecting and measuring aeolian sand transport. It is based on the FlowCapt sensor, an instrument developed to measure aeolian snow transport. This study investigates the performance of the SandFlow in relation to the Saltiphone and the Modified Wilson and Cooke sampler, two devices frequently used in aeolian sand transport. The performance of the SandFlow was tested during three wind erosion events on the Dutch barrier island Terschelling and also in laboratory tests. Results show that the SandFlow adequately registers the periods of aeolian sand transport provided sand transport is sufficiently intense. For low sand transport the SandFlow is less accurate, although the periods with sand transport may still be detected. The sand transport fluxes measured by the SandFlow were lower than those measured by the MWAC although they remained within the same order of magnitude. Laboratory measurements showed that the efficiency of the SandFlow to register sand transport is close to 100% for sand coarser than 300 µm. For finer sand, efficiency decreases rapidly although the instrument remains usable for particles coarser than 150 µm provided appropriate corrections for efficiency are made. This study shows that the SandFlow can be used for aeolian sand transport provided the erosion event is strong enough and the particles are not too fine.

Renewable Energy from Finite Resources: Example of Emerging Photovoltaics
Schmidt, Felix ; Schäffer, Andreas ; Lenz, Markus - \ 2019
Chimia 73 (2019)11. - ISSN 0009-4293 - p. 874 - 879.

Renewable energies, such as sunlight, wind and geothermal heat, are resources that are replaced rapidly by natural processes. However, wind, hydro and solar installations strictly require raw materials that are, in fact, not renewable. Many raw materials are already facing a supply shortage which cannot be easily overcome. This work reviews the problem of critical raw material (CRM) use in photovoltaics (PV) as an example and explains why supply cannot be easily increased to meet demand. We discuss whether there is indeed a 'struggle for elements' in a Darwinian sense, which ultimately leads to a 'survival of the fittest' race in renewable energy technology. In the case of PV, the perception of the definition of 'fittest' needs to change from that considering energy conversion efficiency alone to that which holistically considers net energy produced per emission under the premise that sufficient environmentally and socially acceptable raw material supply exists for renewable energies and all other sectors.

'Higher speeds at night not smart'
Heusinkveld, Bert - \ 2019

Om Nederland uit de stikstofcrisis te trekken, gaat de maximumsnelheid op de snelwegen terug naar 100. Alleen ’s nachts mag 130 nog rijden. Niet slim, vindt meteoroloog Bert Heusinkveld.

Heusinkveld is onderzoeker bij de leerstoelgroep Meteorologie en Luchtkwaliteit. Zijn groep doet veel studie naar de gebeurtenissen in de zogeheten grenslaag, de laag lucht die wij ademen en waar ons weer zich afspeelt.

Waarom is 130 's nachts niet slim?
‘De atmosfeer warmt overdag van onderaf op. Die warme lucht stijgt op en vormt de zogeheten grenslaag, de dunne laag lucht waarin wij leven en ademen. En waarin ook alle vervuiling terechtkomt. ’s Nachts koelt de lucht af, krimpt en vormt een dunne stabiele luchtlaag waarin door afnemende wind nauwelijks nog vermenging plaatsvindt. Een grenslaag die overdag een kilometer dik is, kan ’s nachts krimpen tot slechts honderd meter. Vervuilende stoffen uit het wegverkeer veroorzaken dan een hogere concentratie in die stabiele grenslaag.’

Moet de maatregel dan andersom zijn: overdag 130 en ’s nachts 100?
‘Zo ver wil ik niet gaan. Maar 130 rijden is met het oog op luchtvervuiling overdag minder erg dan ’s nachts. Daar staat tegenover dat er overdag natuurlijk veel meer auto’s rijden dan ’s nachts.’

Dus eigenlijk helemaal geen 130 km/uur?
‘Nee. Een limiet van 130 brengt onrustig rijgedrag met zich mee. Onderlinge snelheidsverschillen leiden sneller tot files en veroorzaken ongevallen. De grote milieuwinst van 100 rijden ontstaat door rustiger rijgedrag en minder files. Een auto in de file stoot per kilometer meer vervuilende stoffen uit dan eentje die kan doorrijden. Maar 130 rijden zorgt voor 30 procent meer vervuiling dan 100.’

Zijn er nog andere meteorologische redenen om juist ’s nachts niet hard te rijden?
‘Ja, het geluid draagt ’s nachts veel verder. Doordat de grenslaag afkoelt, ontstaan flinke verschillen in de temperatuur in die laag. Bovenin kan het wel 10-15 graden warmer zijn dan onderin. In het warmere deel is de geluidsnelheid hoger. Geluid slaat daardoor makkelijker over geluidswallen heen. Het kan zelfs zo zijn dat het effect van zo’n wal daardoor volledig teniet wordt gedaan. Harder rijden in de nacht zorgt daardoor voor meer overlast dan overdag. In Duitsland mogen om die reden auto’s rond steden ’s nacht maar 80. En vrachtauto’s zelfs maar 60.’

Can multi-use of the sea be safe? A framework for risk assessment of multi-use at sea
Hoof, L. van; Burg, S.W.K. van den; Banach, J.L. ; Röckmann, C. ; Goossen, M. - \ 2019
Ocean & Coastal Management (2019). - ISSN 0964-5691
Multi-use at sea - Risk assessment - Risk governance - Seaweed production - Wind farms

By 2050 the world population is expected to reach 10 billion people. This population needs food, water and energy. Increasingly, opportunities are sought out at sea to accommodate these needs. As there is already competition for space, especially in the near-shore, opportunities for multi-use, including the combination of, for example, food and energy production in a single location, are sought. One issue that needs to be addressed to allow for multi-use at sea is safety. Existing frameworks for (marine) risk assessment tend to be rather sector specific and, although existing models and frameworks for risk analysis provide useful elements for an integrated analysis, none of the approaches fully caters for the need of having a framework based on a cyclical process of stakeholder input in all steps of the process of risk identification, risk management and risk evaluation and communication, identifying actions to be taken and providing tools useful in each of the steps, while integrating the three perspectives of maritime safety, food (and feed) safety, and environmental impact assessment and the different perspectives of the actors involved. This study developed a common framework for the risk assessment of multi-use at sea, consisting of six steps (Exploring, Understanding, Appraising, Deciding, Implementing and Evaluating & Communication). The framework encompasses and integrates an analysis of food and feed safety aspects, the safety of people and equipment, and environmental safety aspects. For each step, actions are defined, tools that can be of help to stakeholders are presented, and stakeholder participation measures are described. The framework is iterative and dynamic in its nature; with constant communication and evaluation of progress, decisions can be taken to either take a step forward or back. The framework is developed to assist operators and producers, policymakers, and other stakeholders in assessing and managing risks of multi-use at sea.

Parametrizing Horizontally-Averaged Wind and Temperature Profiles in the Urban Roughness Sublayer
Theeuwes, Natalie E. ; Ronda, Reinder J. ; Harman, Ian N. ; Christen, Andreas ; Grimmond, Sue B. - \ 2019
Boundary-Layer Meteorology 173 (2019)3. - ISSN 0006-8314 - p. 321 - 348.
Roughness sublayer - Temperature profile - Urban canopy - Wind profile

Tower-based measurements from within and above the urban canopy in two cities are used to evaluate several existing approaches that parametrize the vertical profiles of wind speed and temperature within the urban roughness sublayer (RSL). It is shown that current use of Monin–Obukhov similarity theory (MOST) in numerical weather prediction models can be improved upon by using RSL corrections when modelling the vertical profiles of wind speed and friction velocity in the urban RSL using MOST. Using anisotropic building morphological information improves the agreement between observed and parametrized profiles of wind speed and momentum fluxes for selected methods. The largest improvement is found when using dynamically-varying aerodynamic roughness length and displacement height. Adding a RSL correction to MOST, however, does not improve the parametrization of the vertical profiles of temperature and heat fluxes. This is expected since sources and sinks of heat are assumed uniformly distributed through a simple flux boundary condition in all RSL formulations, yet are highly patchy and anisotropic in a real urban context. Our results can be used to inform the choice of surface-layer representations for air quality, dispersion, and numerical weather prediction applications in the urban environment.

Mutagenesis of odorant coreceptor Orco fully disrupts foraging but not oviposition behaviors in the hawkmoth Manduca sexta
Fandino, Richard A. ; Alexander, H. ; Bisch-Knaden, S. ; Zhang, J. ; Bucks, S. ; Nguyen, T.A.T. ; Schröder, K. ; Werckenthin, Achim ; Rybak, J. ; Stengl, Monika ; Knaden, M. ; Hansson, Bill S. ; Groβe-Wilde, Ewald - \ 2019
Proceedings of the National Academy of Sciences of the United States of America 116 (2019)31. - ISSN 0027-8424 - p. 15677 - 15685.
CRISPR-Cas9 - Insect olfaction - Insect-plant interactions - Manduca sexta - Orco

The hawkmoth Manduca sexta and one of its preferred hosts in the North American Southwest, Datura wrightii, share a model insect-plant relationship based on mutualistic and antagonistic life-history traits. D. wrightii is the innately preferred nectar source and oviposition host for M. sexta. Hence, the hawkmoth is an important pollinator while the M. sexta larvae are specialized herbivores of the plant. Olfactory detection of plant volatiles plays a crucial role in the behavior of the hawkmoth. In vivo, the odorant receptor coreceptor (Orco) is an obligatory component for the function of odorant receptors (ORs), a major receptor family involved in insect olfaction. We used CRISPR-Cas9 targeted mutagenesis to knock out (KO) the MsexOrco gene to test the consequences of a loss of OR-mediated olfaction in an insect-plant relationship. Neurophysiological characterization revealed severely reduced antennal and antennal lobe responses to representative odorants emitted by D. wrightii. In a wind-tunnel setting with a flowering plant, Orco KO hawkmoths showed disrupted flight orientation and an ablated proboscis extension response to the natural stimulus. The Orco KO gravid female displayed reduced attraction toward a nonflowering plant. However, more than half of hawkmoths were able to use characteristic odor-directed flight orientation and oviposit on the host plant. Overall, OR-mediated olfaction is essential for foraging and pollination behaviors, but plant-seeking and oviposition behaviors are sustained through additional OR-independent sensory cues.

Oceanic heat transport into the Arctic under high and low CO 2 forcing
Linden, Eveline C. van der; Bars, Dewi Le; Bintanja, Richard ; Hazeleger, Wilco - \ 2019
Climate Dynamics 53 (2019)7-8. - ISSN 0930-7575 - p. 4763 - 4780.
Arctic climate change - Equilibrium climate states - Gyre transport - Nordic Seas - Oceanic heat transport

Enhanced ocean heat transport into the Arctic is linked to stronger future Arctic warming and polar amplification. To quantify the impact of ocean heat transport on Arctic climate, it is imperative to understand how its magnitude and the associated mechanisms change in other climate states. This paper therefore assesses the ocean heat transport into the Arctic at 70 N for climates forced with a broad range of carbon dioxide concentration levels, ranging from one-fourth to four times modern values. We focused on ocean heat transports through the Arctic entrances (Bering Strait, Canadian Archipelago, and Nordic Seas) and identified relative contributions of volume and temperature to these changes. The results show that ocean heat transport differences across the five climate states are dominated by heat transport changes in the Nordic Seas, although in the warmest climate state heat transport through the Bering Strait plays an almost equally important role. This is primarily caused by changes in horizontal currents owing to anomalous wind responses and to differential advection of thermal anomalies. Changes in sea ice cover play a prominent role by modulating the surface heat fluxes and the impact of wind stresses on ocean currents. The Atlantic meridional overturning circulation and its associated heat transport play a more modest role in the ocean heat transport into the Arctic. The net effect of these changes is that the poleward ocean heat transport at 70 N strongly increases from the coldest climate to the warmest climate state.

ENSPRESO - an open, EU-28 wide, transparent and coherent database of wind, solar and biomass energy potentials
Ruiz, P. ; Nijs, W. ; Tarvydas, D. ; Sgobbi, A. ; Zucker, A. ; Pilli, R. ; Jonsson, R. ; Camia, A. ; Thiel, C. ; Hoyer-Klick, C. ; Longa, F. Dalla; Kober, T. ; Badger, J. ; Volker, P. ; Elbersen, B.S. ; Brosowski, A. ; Thrän, D. - \ 2019
Energy Strategy Reviews 26 (2019). - ISSN 2211-467X
Biomass - Energy system model - National - Open data - Potentials - Regional - Renewable - Solar - Wind

Data on the potential generation of energy from wind, solar and biomass is crucial for analysing their development, as it sets the limits on how much additional capacity it is feasible to install. This paper presents the methodologies used for the development of ENSPRESO, ENergy System Potentials for Renewable Energy SOurces, an EU-28 wide, open dataset for energy models on renewable energy potentials, at national and regional levels for the 2010–2050 period. In ENSPRESO, coherent GIS-based land-restriction scenarios are developed. For wind, resource evaluation also considers setback distances, as well as high resolution geo-spatial wind speed data. For solar, potentials are derived from irradiation data and available area for solar applications. Both wind and solar have separately a potential electricity production which is equivalent to three times the EU's 2016 electricity demand, with wind onshore and solar requiring 16% and 1.4% of total land, respectively. For biomass, agriculture, forestry and waste sectors are considered. Their respective sustainable potentials are equivalent to a minimum 10%, 1.5% and 1% of the total EU primary energy use. ENSPRESO can enrich the results of any energy model (e.g. JRC-EU-TIMES) by improving its analyses of the competition and complementarity of energy technologies.

In search of pipistrelle bats: study aims to reveal impact of offshore wind turbines
Lagerveld, S. - \ 2019

Wind turbines on the North Sea are hazardous obstacles for migrating bats. By equipping 500 of the animals with transmitters, WUR is trying to assess the consequences of this. Resource spent a morning with researcher Sander Lagerveld’s bat team.

The consequences of seabird habitat loss from offshore wind turbines, version 2 : Displacement and population level effects in 5 selected species
Kooten, Tobias van; Soudijn, Floor ; Tulp, Ingrid ; Chen, Chun ; Benden, Daniel ; Leopold, Mardik - \ 2019
IJmuiden : Wageningen Marine Research (Wageningen Marine Research report C063/19) - 116
Improving the precision and accuracy of animal population estimates with aerial image object detection
Eikelboom, Jasper A.J. ; Wind, Johan ; Ven, Eline van de; Kenana, Lekishon M. ; Schroder, Bradley ; Knegt, Henrik J. de; Langevelde, Frank van; Prins, Herbert H.T. - \ 2019
Methods in Ecology and Evolution 10 (2019)11. - ISSN 2041-210X - p. 1875 - 1887.
computer vision - convolutional neural network - deep machine learning - drones - game census - image recognition - savanna - wildlife survey

Animal population sizes are often estimated using aerial sample counts by human observers, both for wildlife and livestock. The associated methods of counting remained more or less the same since the 1970s, but suffer from low precision and low accuracy of population estimates. Aerial counts using cost-efficient Unmanned Aerial Vehicles or microlight aircrafts with cameras and an automated animal detection algorithm can potentially improve this precision and accuracy. Therefore, we evaluated the performance of the multi-class convolutional neural network RetinaNet in detecting elephants, giraffes and zebras in aerial images from two Kenyan animal counts. The algorithm detected 95% of the number of elephants, 91% of giraffes and 90% of zebras that were found by four layers of human annotation, of which it correctly detected an extra 2.8% of elephants, 3.8% giraffes and 4.0% zebras that were missed by all humans, while detecting only 1.6 to 5.0 false positives per true positive. Furthermore, the animal detections by the algorithm were less sensitive to the sighting distance than humans were. With such a high recall and precision, we posit it is feasible to replace manual aerial animal count methods (from images and/or directly) by only the manual identification of image bounding boxes selected by the algorithm and then use a correction factor equal to the inverse of the undercounting bias in the calculation of the population estimates. This correction factor causes the standard error of the population estimate to increase slightly compared to a manual method, but this increase can be compensated for when the sampling effort would increase by 23%. However, an increase in sampling effort of 160% to 1,050% can be attained with the same expenses for equipment and personnel using our proposed semi-automatic method compared to a manual method. Therefore, we conclude that our proposed aerial count method will improve the accuracy of population estimates and will decrease the standard error of population estimates by 31% to 67%. Most importantly, this animal detection algorithm has the potential to outperform humans in detecting animals from the air when supplied with images taken at a fixed rate.

The ecology of infrastructure decommissioning in the North Sea: what we need to know and how to achieve it
Fowler, A.M. ; Jørgensen, A.M. ; Coolen, J.W.P. ; Jones, D.O.B. ; Svendsen, J.C. ; Brabant, R. ; Rumes, B. ; Degraer, S. - \ 2019
ICES Journal of Marine Science (2019). - ISSN 1054-3139 - 18 p.
artificial reefs - biodiversity - conservation - decommissioning - ecosystem - marine policy - North Sea - offshore infrastructure - platform - sustainability - wind farm
As decommissioning of oil and gas (O&G) installations intensifies in the North Sea, and worldwide, debate rages regarding the fate of these novel habitats and their associated biota—a debate that has important implications for future decommissioning of offshore wind farms (OWFs). Calls to relax complete removal requirements in some circumstances and allow part of an O&G installation to be left in the marine environment are increasing. Yet knowledge regarding the biological communities that develop on these structures and their ecological role in the North Sea is currently insufficient to inform such decommissioning decisions. To focus debate regarding decommissioning policy and guide ecological research, we review environmental policy objectives in the region, summarize existing knowledge regarding ecological aspects of decommissioning for both O&G and OWF installations, and identify approaches to address knowledge gaps through science–industry collaboration. We find that in some cases complete removal will conflict with other policies regarding protection and restoration of reefs, as well as the conservation of species within the region. Key ecological considerations that are rarely considered during decommissioning decisions are: (i) provision of reef habitat, (ii) productivity of offshore ecosystems, (iii) enhancement of biodiversity, (iv) protection of the seabed from trawling, and (v) enhancement of connectivity. Knowledge gaps within these areas will best be addressed using industry infrastructure and vessels for scientific investigations, re-analysis of historical data held by industry, scientific training of industry personnel, joint research funding opportunities, and trial decommissioning projects.
Oil and gas platforms as artificial substrates for epibenthic North Sea fauna: Effects of location and depth
Schutter, Miriam ; Dorenbosch, Martijn ; Driessen, Floor M.F. ; Lengkeek, Wouter ; Bos, Oscar G. ; Coolen, Joop W.P. - \ 2019
Journal of Sea Research 153 (2019). - ISSN 1385-1101
Hard substrates - benthos - species richness - ROV videos - offshore constructions
Offshore oil and gas platforms, shipwrecks and wind farms are known to act as artificial reefs, attracting a broad range of marine species such as algae, invertebrate species and fish. Using Remotely Operated Vehicle (ROV) videos made for technical inspection of eight Dutch and nine Danish oil and gas platforms, we characterize the abundance and diversity of invertebrates and fish species found on or around these artificial hard substrates. Dutch platforms located in the southern part of the North Sea were at depths ranging from 26 to 46 meters, whereas Danish platforms located about 400 km further north were deeper (40 – 66 m). A total of 38 taxa were identified. The most common species were Mytilus edulis (Mollusca), Metridium senile (Cnidaria) and Asterias rubens (Echinodermata). One non-indigenous species was identified: Mnemiopsis leidyi (Ctenophora). A significant clustering of species communities was found based on geographical location: a southern cluster close to the Dutch shoreline and a northern cluster near Denmark (p=0.01). Species diversity was not significantly different between geographical clusters; however, average Braun-Blanquet abundance was significantly higher on in the northern cluster (p<0.05). Invertebrate and fish communities did not change significantly with depth. However, depth zone was a significant clustering factor (p=0.01): communities closer to the seafloor (maximum depth minus 5 m) were characterized by higher species diversity and species richness compared to communities found closer to the surface (<10 m). Future research should focus on the potential role of habitat complexity, substrate orientation and type, and inter-specific relations in explaining the different communities on offshore platforms.
Ecology of the brown crab (Cancer pagurus) : and production potential for passive fisheries in Dutch offshore wind farms
Tonk, L. ; Rozemeijer, M.J.C. - \ 2019
Yerseke : Wageningen Marine Research (Wageningen Marine Research report C064/19A) - 48
Sky view factor calculations and its application in urban heat island studies
Dirksen, M. ; Ronda, R.J. ; Theeuwes, N.E. ; Pagani, G.A. - \ 2019
Urban Climate 30 (2019). - ISSN 2212-0955
Netherlands - Sky view factor - UHI - Urban planning

The sky view factor (SVF) is essential to describe the urban climatology at scales below 100m. This proxy for net radiation depends on the height of the obstacles in its surroundings. The SVF was calculated from a rasterized point cloud height dataset (with 6 − 10 points per m2). The resulting SVF depends on grid-resolution, search radius and number of directions. Previous research related the diurnal maximum urban heat island (UHI) of the canopy layer to the diurnal temperature range, solar irradiance, wind speed, vegetation fraction and SVF. The goal of this study is to determine the sensitivity of the SVF and the impact on the UHI. Within the Netherlands a test area of 70km2 was selected, including: urban areas, meadows and forests. There is a high sensitivity for grid-resolution. Therefore the impact of the SVFs grid resolution on the maximum UHI is explored. Results show that the fourth largest city within the Netherlands, Utrecht, has a mean diurnal maximum UHI of 3.1 °C using a 1m SVF resolution. But, with a 3m SVF resolution the UHI is on average 0.6 °C lower. This highlights the significance of a fine grid resolution which can capture houses, alleys and trees.

Analysis of urban rainfall from hourly to seasonal scales using high-resolution radar observations in the Netherlands
Manola, Iris ; Steeneveld, Gert Jan ; Uijlenhoet, Remko ; Holtslag, Albert A.M. - \ 2019
International Journal of Climatology (2019). - ISSN 0899-8418
extreme rainfall - rain radar observations - synoptic weather types - urban rainfall

In this article an analysis of urban rainfall from hourly to seasonal scales is conducted for the Netherlands, with a focus on its capital, Amsterdam. In addition, the potential of synoptic weather types and local wind directions to categorize extreme rainfall in Amsterdam is assessed. An analysis of gauge-adjusted daily radar rainfall retrievals with 1 km spatial resolution for 10 years shows that rainfall is enhanced over Dutch cities compared to their rural surroundings, with a maximum of a 14.2% increase over the largest cities in winter. The annual cumulative rainfall in Amsterdam appears to be significantly higher compared to its surroundings. This is due both to the higher frequency of occurrence of urban rainfall and to the higher hourly mean intensities. Extreme hourly rainfall rates appear to be affected by urban areas only in summer. Diurnal and weekly rainfall cycles do not reveal any significant urban influence. A wind direction analysis reveals that extreme rainfall events can primarily be attributed to westerly and next to southerly air masses. An analysis of the Jenkinson and Collinson (JC) and the German Weather Service (Deutscher Wetterdienst, DWD) weather types with rainfall and extreme rainfall events reveals that the JC weather types are more indicative of situations associated with rainfall extremes, whereas the DWD weather types are more indicative of situations resulting in higher accumulated rainfall amounts.

Trends in and closure of the atmospheric angular momentum budget in the 20th century in ERA-20C
Veerman, Menno A. ; Heerwaarden, Chiel C. van - \ 2019
Quarterly Journal of the Royal Meteorological Society 145 (2019)724. - ISSN 0035-9009 - p. 2990 - 3003.
20th century - angular momentum - balance - budget - ERA-20C - trends

It is well known that global warming in the 20th century has influenced the global circulation of the atmosphere. Atmospheric angular momentum (AAM), a measure of the rotation of the atmosphere around the Earth's axis, is a useful quantity to investigate changes in the global atmospheric circulation. In this study, 20th century trends in the AAM budget are determined using the ERA-20C reanalysis data of the European Centre for Medium-Range Weather Forecasts (ECMWF). In addition, the closure of the AAM budget is determined to assess the ability of ERA-20C to conserve angular momentum. The total AAM has increased in the 20th century, associated mainly with an increasing relative (zonal wind) AAM in most of the stratosphere and the tropical upper troposphere, and a poleward redistribution in the midlatitudes. These trends can be related to the warming in the troposphere and cooling in the lower stratosphere found in this study, likely caused by increasing atmospheric CO2 concentrations. The Ω-AAM, representing the rotation of the atmosphere along with the Earth, shows no clear trend, but a spurious peak around 1920. This peak is caused by a global increase in surface pressure and is considered an artefact of changes in the amount of assimilated observations. It is also found that the AAM budget is not well closed in ERA-20C, which is mainly the result of the assimilation of observations during production of the reanalysis. The trends in the AAM budget in ERA-20C are likely affected by changes in the number of assimilated observations and should be validated with other reanalyses in further research.

European mega-heatwaves linked to drought
Vila-Guerau de Arellano, Jordi ; Heerwaarden, Chiel van; Teuling, Ryan - \ 2019

Heatwaves in Europe have become increasingly frequent and intense in recent years. This summer, Western Europe has already been hit by two severe heatwaves. Researchers from Ghent University and Wageningen University & Research have found a common ingredient of such European mega-heatwaves: drought conditions in the regions the wind blows from.

Boven de stad is het nog heter
Heusinkveld, Bert ; Krol, Maarten ; Steeneveld, Gert-Jan - \ 2019

Hitte-eiland Een stad wordt warmer dan het buitengebied, door al die stenen en een gebrek aan wind. Maar tot hoe hoog gaat dat ‘hitte-eiland’ door? Onderzoekers deden unieke proeven, in hartje Amsterdam.

Alarm over smog: risico voor de gezondheid
Heusinkveld, Bert ; Steeneveld, Gert-Jan - \ 2019

In heel Nederland is de kans op zware smog door de hitte en de wind uit het Ruhrgebied zo groot dat de 'alarmdrempel' wordt bereikt. Niet alleen astmapatiënten krijgen last, maar iedereen loopt risico.

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