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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    Interactions among drainage flows, gravity waves and turbulence: a BLLAST case study
    Román Cascón, C. ; Yagüe, C. ; Mahrt, L. ; Sastre, M. ; Steeneveld, G.J. ; Pardyjak, E. ; Boer, A. van de; Hartogensis, O.K. - \ 2015
    Atmospheric Chemistry and Physics 15 (2015). - ISSN 1680-7316 - p. 9031 - 9047.
    stable boundary-layer - intermittent turbulence - density-current - flux - field - wind - disturbances - simulations - stability - dynamics
    The interactions among several stable-boundary-layer (SBL) processes occurring just after the evening transition of 2 July 2011 have been analysed using data from instruments deployed over the area of Lannemezan (France) during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) field campaign. The near-calm situation of the afternoon was followed by the formation of local shallow drainage flows (SDFs) of less than 10 m depth at different locations. The SDF stage ended with the arrival of a stronger wind over a deeper layer more associated with the mountain-plain circulation, which caused mixing and destruction of the SDFs. Several gravity-wave-related oscillations were also observed on different time series. Wavelet analyses and wave parameters were calculated from high resolution and accurate surface pressure data of an array of microbarometers. These waves propagated relatively long distances within the SBL. The effects of these phenomena on turbulent parameters (friction velocity and kinematic heat flux) have been studied through multi-resolution flux decomposition methods performed on high frequency data from sonic anemometers deployed at different heights and locations. With this method, we were able to detect the different time-scales involved in each turbulent parameter and separate them from wave contributions, which becomes very important when choosing averaging-windows for surface flux computations using eddy covariance methods. The extensive instrumentation allowed us to highlight in detail the peculiarities of the surface turbulent parameters in the SBL, where several of the noted processes were interacting and producing important variations in turbulence with height and between sites along the sloping terrain.
    Study of a prototypical convective boundary layer observed during BLLAST: contributions by large-scale forcings
    Pietersen, H.P. ; Vilà-Guerau De Arellano, J. ; Augustin, P. ; Boer, A. van de; Coster, O. de; Delbarre, H. ; Durand, P. ; Fourmentin, M. ; Gioli, B. ; Hartogensis, O.K. ; Lohou, F. ; Lothon, M. ; Ouwersloot, H.G. ; Pino, D. ; Reuder, J. - \ 2015
    Atmospheric Chemistry and Physics 15 (2015). - ISSN 1680-7316 - p. 4241 - 4257.
    large-eddy simulation - turbulence - entrainment - transition - radiation - decay
    We study the influence of the large-scale atmospheric contribution to the dynamics of the convective boundary layer (CBL) in a situation observed during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) field campaign. We employ two modeling approaches, the mixed-layer theory and large-eddy simulation (LES), with a complete data set of surface and upper-air atmospheric observations, to quantify the contributions of the advection of heat and moisture, and subsidence. We find that by only taking surface and entrainment fluxes into account, the boundary-layer height is overestimated by 70 %. Constrained by surface and upper-air observations, we infer the large-scale vertical motions and horizontal advection of heat and moisture. Our findings show that subsidence has a clear diurnal pattern. Supported by the presence of a nearby mountain range, this pattern suggests that not only synoptic scales exert their influence on the boundary layer, but also mesoscale circulations. LES results show a satisfactory correspondence of the vertical structure of turbulent variables with observations. We also find that when large-scale advection and subsidence are included in the simulation, the values for turbulent kinetic energy are lower than without these large-scale forcings. We conclude that the prototypical CBL is a valid representation of the boundary-layer dynamics near regions characterized by complex topography and small-scale surface heterogeneity, provided that surface- and large-scale forcings are representative for the local boundary layer.
    Interactions among gravity waves, shallow drainage flows and turbulence in the stable boundary layer
    Román-Cascón, C. ; Yagüe, C. ; Sastre, M. ; Mahrt, L. ; Steeneveld, G.J. ; Boer, A. van de; Maqueda, G. ; Ander Arrillaga, J. - \ 2015
    The interactions among turbulence and non-turbulent motions have been analysed for a single night using data from the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) field campaign. The peculiarity of this night falls on the observation of several and different stable-boundary-layer (SBL) processes, including local shallow drainage flows, gravity waves and deeper katabatic winds during the SBL formation stage and early night. The local character of the shallow drainage flows (less than ten meters depth) has been analysed using wind and temperature time series at several locations. On the other hand, gravity waves features have been studied using high-frequency and precise data from an array of microbarometers. Finally, the interactions among these submeso motions and turbulence have been studied using data from several sonic anemometers deployed at different heights and locations. Multiscale techniques as wavelet analysis and Multi Resolution Flux Decomposition (MRFD) have been employed to carry out the study and have been demonstrated as very useful for this type of analyses.
    Atmospheric turbulence over crops : confronting theories with observations
    Boer, A. van de - \ 2015
    Wageningen University. Promotor(en): Bert Holtslag, co-promotor(en): Arnold Moene; A. Graf. - Wageningen : Wageningen University - ISBN 9789462572416 - 143
    turbulentie - meteorologie - atmosfeer - gewassen - watergebruiksrendement - transpiratie - modellen - eddy-covariantie - turbulente stroming - turbulence - meteorology - atmosphere - crops - water use efficiency - transpiration - models - eddy covariance - turbulent flow

    Atmospheric turbulence plays a key role in hydrological and carbon cycles, and in weather and climate. Understanding and forecasting turbulence is thereby relevant for human life and environment.

    We deal with some major challenges for studying atmospheric turbulence over crops. Land-atmosphere interactions are specifically complex because of surface heterogeneity. Also, boundary-layer entrainment complicates measuring and studying surface fluxes. Furthermore, the absence of high-frequency observations and of measurements of underlying soil and vegetation processes impedes studying land-atmosphere interactions.

    We show the applicability of analytical footprint models over a heterogeneous land surface, and the validity of Monin-Obukhov similarity theory for a strongly-convective boundary-layer. Moreover, we present improvements on a scheme that can be used to estimate the amount of atmospheric turbulence from single-level weather data. We furthermore suggest to improve the partitioning theory that is used to distinguish soil processes from plant processes in eddy-covariance flux observations.

    The BLLAST field experiment: Boundary-Layer Late Afternoon and Sunset Turbulence
    Lothon, M. ; Lohou, F. ; Pino, D. ; Vilà-Guerau De Arellano, J. ; Hartogensis, O.K. ; Boer, A. van de; Coster, O. de; Moene, A.F. ; Steeneveld, G.J. - \ 2014
    Atmospheric Chemistry and Physics 14 (2014). - ISSN 1680-7316 - p. 10931 - 10960.
    large-eddy-simulation - observed evening transition - doppler spectral width - low-level jets - convective turbulence - intermittent turbulence - surface-layer - kinetic-energy - drainage flow - length scales
    Due to the major role of the sun in heating the earth's surface, the atmospheric planetary boundary layer over land is inherently marked by a diurnal cycle. The afternoon transition, the period of the day that connects the daytime dry convective boundary layer to the night-time stable boundary layer, still has a number of unanswered scientific questions. This phase of the diurnal cycle is challenging from both modelling and observational perspectives: it is transitory, most of the forcings are small or null and the turbulence regime changes from fully convective, close to homogeneous and isotropic, toward a more heterogeneous and intermittent state. These issues motivated the BLLAST (Boundary-Layer Late Afternoon and Sunset Turbulence) field campaign that was conducted from 14 June to 8 July 2011 in southern France, in an area of complex and heterogeneous terrain. A wide range of instrumented platforms including full-size aircraft, remotely piloted aircraft systems, remote-sensing instruments, radiosoundings, tethered balloons, surface flux stations and various meteorological towers were deployed over different surface types. The boundary layer, from the earth's surface to the free troposphere, was probed during the entire day, with a focus and intense observation periods that were conducted from midday until sunset. The BLLAST field campaign also provided an opportunity to test innovative measurement systems, such as new miniaturized sensors, and a new technique for frequent radiosoundings of the low troposphere. Twelve fair weather days displaying various meteorological conditions were extensively documented during the field experiment. The boundary-layer growth varied from one day to another depending on many contributions including stability, advection, subsidence, the state of the previous day's residual layer, as well as local, meso- or synoptic scale conditions. Ground-based measurements combined with tethered-balloon and airborne observations captured the turbulence decay from the surface throughout the whole boundary layer and documented the evolution of the turbulence characteristic length scales during the transition period. Closely integrated with the field experiment, numerical studies are now underway with a complete hierarchy of models to support the data interpretation and improve the model representations.
    Estimation of surface fluxes and optical turbulence from standard weather-station observations
    Boer, A. van de; Moene, A.F. ; Graf, A. ; Simmer, C. ; Holtslag, A.A.M. - \ 2014
    Estimation of optical turbulence with standard weather-station observations
    Boer, A. van de; Moene, A.F. ; Graf, A. ; Simmer, C. ; Holtslag, A.A.M. - \ 2014
    Estimation of the refractive index structure parameter from single-level daytime routine weather data
    Boer, A. van de; Moene, A.F. ; Graf, A. ; Simmer, C. ; Holtslag, A.A.M. - \ 2014
    Applied Optics 53 (2014)26. - ISSN 1559-128X - p. 5944 - 5960.
    obukhov similarity functions - water-vapor - optical turbulence - sonic anemometer - surface fluxes - energy-balance - temperature - radiation - land - heat
    Atmospheric scintillations cause difficulties for applications where an undistorted propagation of electromagnetic radiation is essential. These scintillations are related to turbulent fluctuations of temperature and humidity that are in turn related to surface heat fluxes. We developed an approach that quantifies these scintillations by estimating Cn2 from surface fluxes that are derived from single-level routine weather data. In contrast to previous methods that are biased to dry and warm air, our method is directly applicable to several land surface types, environmental conditions, wavelengths, and measurement heights (lookup tables for a limited number of site-specific parameters are provided). The approach allows for an efficient evaluation of the performance of, e.g., infrared imaging systems, laser geodetic systems, and ground-to-satellite optical communication systems.We tested our approach for two grass fields in central and southern Europe, and for a wheat field in central Europe. Although there are uncertainties in the flux estimates, the impact on Cn2 is shown to be rather small. The Cn2 daytime estimates agree well with values determined from eddy covariance measurements for the application to the three fields. However, some adjustments were needed for the approach for the grass in southern Europe because of non-negligible boundary-layer processes that occur in addition to surface-layer processes.
    Intercomparison of Methods for the Simultaneous Estimation of Zero-Plane Displacement and Aerodynamic Roughness Length from Single-Level Eddy-Covariance Data
    Graf, A. ; Boer, A. van de; Moene, A.F. ; Vereecken, H. - \ 2014
    Boundary-Layer Meteorology 151 (2014)2. - ISSN 0006-8314 - p. 373 - 387.
    frequency-response corrections - atmospheric boundary-layer - sonic anemometer data - tall vegetation - sensible-heat - surface - parameters - height - flux - temperature
    We applied three approaches to estimate the zero-plane displacement d through the aerodynamic measurement height z (with z = zm - d and zm being the measurement height above the surface), and the aerodynamic roughness length z0, from single-level eddy covariance data. Two approaches (one iterative and one regression-based) were based on the universal function in the logarithmic wind profile and yielded an inherently simultaneous estimation of both d and z0. The third approach was based on flux–variance similarity, where estimation of d and consecutive estimation of z0 are independent steps. Each approach was further divided into two methods differing either with respect to the solution technique (profile approaches) or with respect to the variable (variance of vertical wind and temperature, respectively). All methods were applied to measurements above a large, growing wheat field where a uniform canopy height and its frequent monitoring provided plausibility limits for the resulting estimates of time-variant d and z0. After applying, for each approach, a specific data filtering that accounted for the range of conditions (e.g. stability) for which it is valid, five of the six methods were able to describe the temporal changes of roughness parameters associated with crop growth and harvest, and four of them agreed on d to within 0.3 m most of the time. Application of the same methods to measurements with a more heterogeneous footprint consisting of fully-grown sugarbeet and a varying contribution of adjacent harvested fields exhibited a plausible dependence of the roughness parameters on the sugarbeet fraction. It also revealed that the methods producing the largest outliers can differ between site conditions and stability. We therefore conclude that when determining d for canopies with unknown properties from single-level measurements, as is increasingly done, it is important to compare the results of a number of methods rather than rely on a single one. An ensemble average or median of the results, possibly after elimination of methods that produce outliers, can help to yield more robust estimates. The estimates of z0 were almost exclusively physically plausible, although d was considered unknown and estimated simultaneously with the methods and results described above
    Detection of Entrainment Influences on Surface-Layer Measurements and Extension of Monin–Obukhov Similarity Theory
    Boer, A. van de; Moene, A.F. ; Graf, A. ; Schüttemeyer, D. ; Simmer, C. - \ 2014
    Boundary-Layer Meteorology 152 (2014)1. - ISSN 0006-8314 - p. 19 - 44.
    convective boundary-layer - temperature-humidity correlation - sonic anemometer - analytical-model - mixed-layer - turbulence - fluxes - transport - water - heat
    We present a method to detect influences of boundary-layer processes on surface-layer measurements, using statistics and spectra of surface-layer variables only. We validated our detection method with boundary-layer measurements. Furthermore, we confirm that Monin–Obukhov similarity functions fit well to temperature-variance data obtained at two different homogeneous surfaces. However, we found that humidity variance measurements deviate from the universal functions above one of the two studied surfaces for days on which entrained air reached the surface layer. These results confirm that Monin–Obukhov similarity theory should be used with care in the analysis of surface-layer data. Finally, we propose the use of an extra term in flux-variance relations that depends on the entrainment ratio for humidity and on the boundary-layer height. If boundary-layer measurements are not available, we show how the entrainment ratio for humidity can be approximated from the skewness of the humidity distribution
    Role of the residual layer and large-scale subsidence on the development and evolution of the convective boundary layer
    Blay-Carreras, E. ; Pino, D. ; Vilà-Guerau de Arellano, J. ; Boer, A. van de; Coster, O. de; Darbieu, C. ; Hartogensis, O.K. ; Lohou, F. ; Lothon, M. ; Pietersen, H.P. - \ 2014
    Atmospheric Chemistry and Physics 14 (2014). - ISSN 1680-7316 - p. 4515 - 4530.
    large-eddy-simulation - morning transition - carbon-dioxide - mixed-layer - water-vapor - order-jump - part i - turbulence - entrainment - inversion
    Observations, mixed-layer theory and the Dutch Large-Eddy Simulation model (DALES) are used to analyze the dynamics of the boundary layer during an intensive operational period (1 July 2011) of the Boundary Layer Late Afternoon and Sunset Turbulence campaign. Continuous measurements made by remote sensing and in situ instruments in combination with radio soundings, and measurements done by remotely piloted aircraft systems and two manned aircrafts probed the vertical structure and the temporal evolution of the boundary layer during the campaign. The initial vertical profiles of potential temperature, specific humidity and wind, and the temporal evolution of the surface heat and moisture fluxes prescribed in the models runs are inspired by some of these observations. The research focuses on the role played by the residual layer during the morning transition and by the large-scale subsidence on the evolution of the boundary layer. By using DALES, we show the importance of the dynamics of the boundary layer during the previous night in the development of the boundary layer at the morning. DALES numerical experiments including the residual layer are capable of modeling the observed sudden increase of the boundary-layer depth during the morning transition and the subsequent evolution of the boundary layer. These simulations show a large increase of the entrainment buoyancy flux when the residual layer is incorporated into the mixed layer. We also examine how the inclusion of the residual layer above a shallow convective boundary layer modifies the turbulent kinetic energy budget. Large-scale subsidence mainly acts when the boundary layer is fully developed, and, for the studied day, it is necessary to be considered to reproduce the afternoon observations. Finally, we also investigate how carbon dioxide (CO2) mixing ratio stored the previous night in the residual layer plays a fundamental role in the evolution of the CO2 mixing ratio during the following day.
    Cn2 from single-level weather data
    Boer, A. van de; Moene, A.F. ; Graf, A. ; Simmer, C. ; Holtslag, A.A.M. - \ 2013
    Entrainment influences on surface layer measurements: detection, and impact on Monin-Obukhov similarity theory
    Boer, A. van de; Moene, A.F. ; Graf, A. - \ 2013
    Validation of a minimum microclimate disturbance chamber for net ecosystem flux measurements
    Graf, A. ; Werner, J. ; Langensiepen, M. ; Boer, A. van de; Schmidt, M. ; Kupisch, M. ; Vereecken, H. - \ 2013
    Agricultural and Forest Meteorology 174-175 (2013). - ISSN 0168-1923 - p. 1 - 14.
    energy-balance closure - carbon-dioxide efflux - canopy gas-exchange - soil co2 efflux - eddy-covariance - grassland ecosystems - sonic anemometer - dynamic chamber - n2o emissions - system
    A minimum-disturbance chamber for canopy net CO2 and H2O flux measurements is described. The system is a passively (optionally actively) ventilated tunnel with large (similar to 0.14 m2) in- and outlet cross sections covering a surface area of approximately 1.6 m2. A differential, non-drying closed-path gas analyzer is used to minimize the requirement for concentration build-ups or drawdowns between the in- and outlet, and 0.05 mm thick FEP (fluorinated ethylene propylene) film is used as top and wall material to minimize radiation modifications. First measurement results in passively ventilated mode are presented from two different sites: a wheat field at a lowland site in the westernmost part of Germany, and differently cropped adjacent fields in the Pyrenee foothills in France, including grassland and a cereal-dominated crop mixture for fodder production. Flux estimates derived from measurements over 20–30 min deployments were compared to concurrent observations by three eddy covariance (EC) stations. The system compared well to EC measurements, with bias of -6.6% for latent heat flux and +9.0% for CO2 flux (R2 = 0.78 and 0.74, respectively). The presence of the chamber causes a reduction of less than 4% in incoming shortwave radiation, and an increase of about 18% in downward longwave radiation. Near the outlet, CO2 concentration was on average modified by -3% with respect to outside conditions, water vapour concentration by +22%, and temperature by +0.9 K, staying below published modifications of a comparable non-steady-state chamber closed for 2 min. Ventilation speed varied by less than 9% across the inlet cross section. Limitations include a minimum wind speed requirement that can be set as low as 0.2 m s-1 for a raw data logging frequency of 1 s-1 or higher, but would need to be higher for slow-response gas analyzers. At the same time, a measurement period of 10 min or more is recommended to minimize random errors from storage term fluctuations. A correction for the added water vapour volume by evapotranspiration is derived and tested, which typically affects H2O flux itself by less than +2% and CO2 flux measurements by 1 µmol/J latent heat
    Intercomparison of methods for the estimation of displacement height and roughness length from single-level eddy covariance data
    Graf, A. ; Boer, A. van de; Schüttemeyer, D. ; Moene, A.F. ; Vereecken, H. - \ 2013
    Turbulentie meten/voorspellen zonder dure apparaten
    Boer, A. van de - \ 2013
    Meteorologica / Nederlandse Vereniging van Beroeps Meteorologen 22 (2013). - ISSN 0929-1504 - p. 13 - 13.
    Berichten van het Buys-Ballot herfstsymposium 2013
    Barbaro, E.W. ; Boer, A. van de; Giesen, R. ; Ligtenberg, S. ; Stap, L. ; Sterk, H.A.M. - \ 2013
    Meteorologica / Nederlandse Vereniging van Beroeps Meteorologen 22 (2013)4. - ISSN 0929-1504 - p. 12 - 13.
    WRF simulations of the atmospheric boundary layer evening transitions during the BLLAST field campaign
    Sastre Marugán, M. ; Steeneveld, G.J. ; Yagüe, C. ; Román-Cascón, C. ; Maqueda, G. ; Boer, A. van de - \ 2013
    Sensitivity and uncertainty of analytical footprint models according to a combined natural tracer and ensemble approach
    Boer, A. van de; Moene, A.F. ; Schüttemeyer, D. ; Graf, A. - \ 2013
    Agricultural and Forest Meteorology 169 (2013). - ISSN 0168-1923 - p. 1 - 11.
    flux measurements - sonic anemometer - carbon-dioxide - surface-layer - water-vapor - exchange - heat - validation - efflux - fetch
    Evaluations of analytical footprint models using data from several stations located in different land use types are still scarce, but valuable for defining the spatial context of the measurements. Therefore, we evaluated two analytical footprint models by applying a ‘forward’ and an ‘inversion’ method. We used eddy covariance measurements from a flat agricultural landscape in western Germany in the summer of 2009, with seven eddy covariance systems over three different land use types with contrasting sensible heat fluxes. We found that the model of Hsieh et al. (2000. Adv. Water Resour. 23, 765–772) and of Kormann and Meixner (2001. Boundary Layer Meteorol. 99, 207–224) are both overestimating the distance of the peak contribution of the footprint. In our evaluation, the former model performs slightly better, independent of whether the crosswind dispersion was used from the latter model, or from the proposed model by Detto et al. (2006. Water Resour. Res. 42, 1–16).
    Samenvatting Buys Ballot symposium 2012
    Beelen, A. van; Boer, A. van de; Combe, M. ; Pelt, W. van; Rugenstein, M. ; Sterk, H.A.M. ; Wessem, M. van; Winter, R. de; Steeneveld, G.J. - \ 2012
    Meteorologica / Nederlandse Vereniging van Beroeps Meteorologen 21 (2012)4. - ISSN 0929-1504 - p. 22 - 27.
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