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 / 60

    • help
    • print

      Print search results

    • export

      Export search results

    Check title to add to marked list
    Land surface impacts on precipitation in the Netherlands
    Daniels, E.E. - \ 2016
    Wageningen University. Promotor(en): Bert Holtslag, co-promotor(en): Ronald Hutjes; G. Lenderink. - Wageningen : Wageningen University - ISBN 9789462576674 - 151
    precipitation - land surface - land - environmental impact - land use - climatic change - urban areas - weather patterns - netherlands - neerslag - aardoppervlak - land - milieueffect - landgebruik - klimaatverandering - stedelijke gebieden - weerpatronen - nederland
    Dit proefschrift bestudeert de effecten van landgebruiksveranderingen uit het verleden en in de toekomst op neerslag in Nederland door middel van analyses van gemeten regendata en het gebruik van een weermodel.
    Interactions between aerosal and convective boundary-layer dynamics over land
    Wilde Barbaro, E. - \ 2015
    Wageningen University. Promotor(en): Maarten Krol; Bert Holtslag, co-promotor(en): Jordi Vila-Guerau de Arellano. - Wageningen : Wageningen University - ISBN 9789462572652 - 182
    aërosolen - atmosferische grenslaag - grenslaagmeteorologie - aardoppervlak - modellen - simulatiemodellen - straling - atmosfeer - aerosols - atmospheric boundary-layer - boundary-layer meteorology - land surface - models - simulation models - radiation - atmosphere

    In this Section, we summarize the most important findings and relevant issues treated in detail in Chapters 2 to 5.

    The primary conclusion of this thesis is that it is necessary to take aerosols into account to accurately describe the convective atmospheric boundary-layer (CBL) dynamics and the land-surface processes. We reached this conclusion by systematically studying the land-CBL system and its couplings, and employed a hierarchy of models ranging from an eddy-resolving model (large-eddy simulation; LES) to non-eddy resolving models (mixed-layer model, and single column model). In addition to the numerical component, we used a complete observational data set to help us design and evaluate our numerical framework.

    Chapter 2 was devoted to the explanation of the radiative transfer code used in Chapters 4 and 5. We showed that despite the simplified treatment of solar radiation and its interactions with aerosols, our radiative code is in general agreement with a more sophisticated radiative transfer code, even for extreme aerosol loads. Moreover, our results reproduce observations of direct and diffuse radiation at the surface accordingly - as shown in Chapter 4.

    Regarding the longwave band, we showed that aerosols are not relevant for the estimation of the incoming longwave radiation at the surface. We concluded that Brunt's formula, depending only on screen level temperature and vapor pressure, is the most adequate to represent the incoming longwave radiation at the surface for the cases relevant for our studies.

    In Chapter 3 we investigated the impact of aerosol heat absorption on the dynamics of an idealized CBL with prescribed surface fluxes. We found that the structure and evolution of the CBL were influenced by the vertical distribution of the aerosols. Moreover, we showed that the aerosols influence the exchange of heat between the CBL and the free troposphere by (i) extinction of radiation and consequently reduced surface fluxes, and by (ii) deepening the entrainment zone depth. We highlighted the importance of high-resolution models to properly represent the effects of aerosol absorption of radiation on the dynamics of the CBL, especially in the entrainment zone. We demonstrated that, in addition to the properties of the aerosols, the vertical distribution is an important characteristic to properly describe the CBL height evolution and the dynamics of the upper part of the CBL. To further support the analysis of the LES results, we used a mixed-layer (MXL) model to calculate boundary-layer depth and the potential temperature jump at the inversion layer. In spite of the simplicity of this model, the mixed-layer results obtained for boundary-layer height and the inversion layer jump agreed well with the LES results.

    Extending the knowledge acquired with the academical prototypical experiments performed in Chapter 3, in Chapter 4 we quantified the effects of aerosol scattering and absorption of shortwave (SW) radiation both on the surface energy budget and on the CBL dynamics. To this end, we coupled our LES model and the MXL model to (i) a land-surface model and (ii) a broadband SW radiative transfer model, (described in Chapter 2). We successfully validated the results obtained with the LES model and MXL model using measurements of (thermo)dynamic variables and aerosol properties observed in Cabauw (the Netherlands). Our LES results showed that for Cabauw (over well-watered grassland) aerosols significantly alter the magnitude of the available energy at the surface and its partitioning. Under well-watered conditions, the sensible heat flux was more strongly reduced compared to the latent heat flux. Given the satisfactory agreement between the LES results and MXL model results, we further explored the sensitivity of the land-CBL system to a wide range of aerosol optical depths and single scattering albedos using the MXL model. Our results showed that higher loads of aerosols impose an energy restriction at the surface. As a result, we calculated a delay in the morning onset of the CBL and an advance in the CBL afternoon collapse. We also found that entrainment of aerosols from the residual layer plays a significant role in the development of the CBL dynamics during the day. An important aspect of Chapter 4 is the investigation of the different responses of the CBL dynamics depending on aerosol optical properties. Strongly absorbing aerosols deepened and warmed the CBL, while purely scattering aerosols shallowed and cooled the CBL.

    We highlighted that the results presented in Chapter 4 can be used as a benchmark to evaluate coupling and performance of the parametrizations for SW radiation, land-surface and boundary-layer schemes, implemented in mesoscale or global chemistry transport models.

    In Chapter 5 we increased the complexity of our land-CBL system representation by studying the formation and transport of ammonium nitrate aerosols. In doing so, we coupled in our LES radiation, chemistry, aerosols, CBL dynamics, and surface exchange processes of chemicals, heat and moisture. Our fully coupled LES model was again evaluated against observations of chemistry and aerosol fields and showed a good correspondence. In particular, our results showed a satisfactory agreement between the simulated and observed nitrate partitioning at the surface.

    We showed that gas-aerosol conversion of nitrate leads to highly non-linear profiles of nitrate concentrations and turbulent fluxes. Moreover, the shapes of the simulated profiles depended strongly on the time scale of gas-aerosol conversions. Note that the typical timescale of turbulent motions in the CBL is around 10-20 minutes. For shorter time scales of gas-aerosol conversion compared to the CBL dynamics timescale, we found that turbulent fluxes are larger and concentration profiles more tilted within the CBL. These results have a significant impact on the nitrate deposition flux at the surface. Our LES results confirmed that the large deposition velocities for aerosol nitrate close to the surface are actually due to outgassing of aerosol nitrate rather than a real deposition process.

    An important aspect discussed in Chapter 5 concerns the inability of non-eddy resolving models to accurately model the turbulent transport of nitrate within the CBL. Based on a detailed analysis of the flux budget equation, we showed that the exchange coefficient of heat used in our 1D model has to be increased to better account for the complex interaction between gas-aerosol conversion of nitrate and 3D turbulence within the CBL. Indeed, the new exchange coefficient also improved the comparison between gas-aerosol partitioning of nitrate calculated with our 1D model and surface observations.

    The results discussed in this thesis demonstrate the need for considering the influence of aerosols on the CBL dynamics. Specifically, aerosols influence important phenomena for the CBL evolution namely radiation, surface-atmosphere interactions, chemistry, and (thermo)dynamics. In addition to that, the availability of high-resolution numerical simulations is crucial to validate and evaluate results obtained by numerical models that do not explicitly resolve the turbulent field.

    Regional atmospheric feedbacks over land and coastal areas
    Maat, H.W. ter - \ 2014
    Wageningen University. Promotor(en): Bert Holtslag; Pavel Kabat, co-promotor(en): Ronald Hutjes. - Wageningen : Wageningen University - ISBN 9789461737731 - 172
    atmosfeer - aardoppervlak - kustgebieden - koolstofcyclus - kooldioxide - landgebruik - neerslag - gematigd klimaat - semi-aride klimaat - modellen - nederland - saoedi-arabië - atmosphere - land surface - coastal areas - carbon cycle - carbon dioxide - land use - precipitation - temperate climate - semiarid climate - models - netherlands - saudi arabia
    De afgelopen jaren is er een grotere vraag ontstaan naar klimaat- en weergegevens op lokaal niveau, nu en in de toekomst. Van regionale klimaatmodellen wordt verwacht dat zij dit kunnen geven met verbeterde informatie wat betreft extremen. Heterogeniteit moet daartoe verder uitgewerkt worden. Vier verschillende voorbeelden worden behandeld om het begrip te verbeteren van de processen en de terugkoppelingen op lokaal/regionaal niveau. Terugkoppelingen tussen aardoppervlak en de atmosfeer. Drie voorbeelden stammen uit Nederland (gematigd klimaat), de vierde is afkomstig uit het (semi-)aride Saoedi Arabië. Dit proefschrift doet aanbevelingen om regionale atmosferische modellen te verbeteren.
    Effect of the land surface on precipitation events in the Netherlands
    Daniels, E.E. - \ 2012
    Kennis voor Klimaat
    aardoppervlak - grondbedekking - neerslag - nederland - land surface - ground cover - precipitation - netherlands
    Factsheet about a research project investigating the influence of the land surface and (historical) land cover changes on regional precipitation events.
    Drought at the global scale in the 2nd part of the 20th century (1963-2001)
    Huijgevoort, M.H.J. van; Hazenberg, P. ; Lanen, H.A.J. van; Bertrand, N. ; Clark, D. ; Folwell, S. ; Gosling, S. ; Hanasaki, N. ; Heinke, J. ; Stacke, T. ; Voss, F. - \ 2011
    Brussel : European Commission (Technical report / WATCH no. 42) - 40
    droogte - hydrologische gegevens - aardoppervlak - modellen - hydrologie - klimatologie - geschiedenis - drought - hydrological data - land surface - models - hydrology - climatology - history
    The large impacts of drought on society, economy and environment urge for a thorough investigation. A good knowledge of past drought events is important for both understanding of the processes causing drought, as well as to provide reliability assessments for drought projections for the future. Preferably, the investigation of historic drought events should rely on observations. Unfortunately, for a global scale these detailed observations are often not available. Therefore, the outcome of global hydrological models (GHMs) and off-line land surface models (LSMs) is used to assess droughts. In this study we have investigated to what extent simulated gridded time series from these large-scale models capture historic hydrological drought events. Results of ten different models, both GHMs and LSMs, made available by the WATCH project, were compared. All models are run on a global 0.5 degree grid for the period 1963-2000 with the same meteorological forcing data (WATCH forcing data). To identify hydrological drought events, the monthly aggregated total runoff values were used. Different methods were developed to identify spatio-temporal drought characteristics. General drought characteristics for each grid cell, as for example the average drought duration, were compared. These characteristics show that when comparing absolute values the models give substantially different results, whereas relative values lead to more or less the same drought pattern. Next to the general drought characteristics, some documented major historical drought events (one for each continent) were selected and described in more detail. For each drought event, the simulated drought clusters (spatial events) and their characteristics are given for one month during the event. It can be concluded that most major drought events are captured by all models. However, the spatial extent of the drought events differ substantially between the models. In general the models show a fast reaction to rainfall and therefore also capture drought events caused by large rainfall anomalies. More research is still needed, since here we only looked at a few selected number of documented drought events spread over the globe. To assess more in detail if these large-scale models are able to capture drought, additional quantitative analyses are needed together with a more elaborated comparison against observed drought events.
    Simulation of low flows and drought events in WATCH test basins: impact of climate forcing datasets
    Huijgevoort, M.H.J. van; Loon, A.F. van; Hanel, M. ; Haddeland, I. ; Horvát, O. ; Koutroulis, A. ; Machlica, A. ; Weedon, G.P. ; Fendeková, M. ; Tsanis, I. ; Lanen, H.A.J. van - \ 2011
    2011 : European Commission (Technical report / WATCH no. 44) - 19
    geohydrologie - gegevensanalyse - resolutie - aardoppervlak - afvloeiingswater - bodemwater - klimatologie - evaporatie - geohydrology - data analysis - resolution - land surface - runoff water - soil water - climatology - evaporation
    The impact of both spatial and temporal resolution on the components of the terrestrial hydrological cycle are investigated using the WATCH forcing dataset (WFD) and the JULES (Joint UK Land Environment Simulator) land surface model. The various spatial resolutions are achieved by degrading the native half degree latitude/longitude resolution WATCH dataset to both one degree and two degrees. The temporal resolutions are created by degrading the native three hourly WATCH forcing dataset to six hourly and using the WATCH interpolator to derive a one hour forcing dataset. There is little difference in the moisture stores of soil water and canopy water in the long term mean from the various resolutions, so the analysis presented is for the changes in evaporation and runoff. The evaporation is further analysed into its various components for the spatial resolution. Results suggest that there is little impact from spatial resolution, but the interpolation method for temporal resolution can have a significant effect on the total mean evaporation/runoff balance.
    Seasonal evaluation of the land surface sheme HTESSEL against remote sensing derived energy fluxes of the Transdanubian regions in Hungary
    Wipfler, E.L. ; Metselaar, K. ; Dam, J.C. van; Feddes, R.A. ; Meijgaard, E. van; Ulft, L.H. van; Hurk, B. van den; Zwart, S.J. ; Bastiaanssen, W.G.M. - \ 2011
    Hydrology and Earth System Sciences 15 (2011)4. - ISSN 1027-5606 - p. 1257 - 1271.
    aardoppervlak - evapotranspiratie - remote sensing - klimaatverandering - modellen - hongarije - land surface - evapotranspiration - remote sensing - climatic change - models - hungary - terrestrial water storage - era-40 reanalysis - balance closure - climate models - field - atmosphere - hydrology - impact - basin
    The skill of the land surface model HTESSEL is assessed to reproduce evaporation in response to land surface characteristics and atmospheric forcing, both being spatially variable. Evaporation estimates for the 2005 growing season are inferred from satellite observations of the Western part of Hungary and compared to model outcomes. Atmospheric forcings are obtained from a hindcast run with the Regional Climate Model RACMO2. Although HTESSEL slightly underpredicts the seasonal evaporative fraction as compared to satellite estimates, the mean, 10th and 90th percentile of this variable are of the same magnitude as the satellite observations. The initial water as stored in the soil and snow layer does not have a significant effect on the statistical properties of the evaporative fraction. However, the spatial distribution of the initial soil and snow water significantly affects the spatial distribution of the calculated evaporative fraction and the models ability to reproduce evaporation correctly in low precipitation areas in the considered region. HTESSEL performs weaker in dryer areas. In Western Hungary these areas are situated in the Danube valley, which is partly covered by irrigated cropland and which also may be affected by shallow groundwater. Incorporating (lateral) groundwater flow and irrigation, processes that are not included now, may improve HTESSELs ability to predict evaporation correctly. Evaluation of the model skills using other test areas and larger evaluation periods is needed to confirm the results.
    Surface evaporation and water vapor transport in the convective boundary layer
    Heerwaarden, C.C. van - \ 2011
    Wageningen University. Promotor(en): Bert Holtslag, co-promotor(en): J. Vila -Guerau de Arellano. - [S.l.] : s.n. - ISBN 9789085859130 - 156
    evaporatie - aardoppervlak - atmosfeer - grenslaag - evaporation - land surface - atmosphere - boundary layer - cum laude
    cum laude graduation (with distinction)
    Initial results from Phase 2 of the of the international urban energy balance comparison project
    Grimmond, C.S.B. ; Blackett, M. ; Best, M.J. ; Baik, J.J. ; Belcher, S.E. ; Steeneveld, G.J. - \ 2011
    International Journal of Climatology 31 (2011)2. - ISSN 0899-8418 - p. 244 - 272.
    stedelijke gebieden - energiebalans - modellen - vergelijkingen - aardoppervlak - urban areas - energy balance - models - comparisons - land surface - submesoscale soil model - regular building arrays - global climate model - canopy model - heat-storage - teb scheme - 2 cities - thermal-properties - street canyons - boundary-layer
    Urban land surface schemes have been developed to model the distinct features of the urban surface and the associated energy exchange processes. These models have been developed for a range of purposes and make different assumptions related to the inclusion and representation of the relevant processes. Here, the first results of Phase 2 from an international comparison project to evaluate 32 urban land surface schemes are presented. This is the first large-scale systematic evaluation of these models. In four stages, participants were given increasingly detailed information about an urban site for which urban fluxes were directly observed. At each stage, each group returned their models' calculated surface energy balance fluxes. Wide variations are evident in the performance of the models for individual fluxes. No individual model performs best for all fluxes. Providing additional information about the surface generally results in better performance. However, there is clear evidence that poor choice of parameter values can cause a large drop in performance for models that otherwise perform well. As many models do not perform well across all fluxes, there is need for caution in their application, and users should be aware of the implications for applications and decision making
    Dis-aggregation of airborne flux measurements using footprint analysis
    Hutjes, R.W.A. ; Vellinga, O.S. ; Gioli, B. ; Miglietta, F. - \ 2010
    Agricultural and Forest Meteorology 150 (2010)7-8. - ISSN 0168-1923 - p. 966 - 983.
    klimaatverandering - landgebruik - emissie - aardoppervlak - methodologie - climatic change - land use - emission - land surface - methodology - boundary-layer - carbon-dioxide - scalar fluxes - quality assessment - least-squares - heat fluxes - part 1 - aircraft - surface - tower
    Aircraft measurements of turbulent fluxes are generally being made with the objective to obtain an estimate of regional exchanges between land surface and atmosphere, to investigate the spatial variability of these fluxes, but also to learn something about the fluxes from some or all of the land cover types that make up the landscape. In this study we develop a method addressing this last objective, an approach to disentangle blended fluxes from a landscape into the component fluxes emanating from the various land cover classes making up that landscape. The method relies on using a footprint model to determine which part of the landscape the airborne flux observation refers to, using a high resolution land cover map to determine the fractional covers of the various land cover classes within that footprint, and finally using multiple linear regression on many such flux/fractional cover data records to estimate the component fluxes. The method is developed in the context of three case studies of increasing complexity and the analysis covers three scalar fluxes: sensible and latent heat fluxes and carbon dioxide flux, as well as the momentum flux. A basic assumption under the dis-aggregation method is that the composite flux, i.e. the landscape flux, is a linear average of the component fluxes, i.e. the fluxes from the various land elements. We test and justify this assumption by comparing linear averages of component fluxes in simple ‘binary landscapes’, weighted by their relative area, with directly aircraft observed fluxes. In all case studies dis-aggregation of mixed values for fluxes from heterogeneous areas into component land cover class specific fluxes is feasible using robust least squares regression, both in simple binary ‘landscapes’ and in more complex cases. Both the differences between land cover classes and the differences between synoptic conditions can be resolved, for those land cover classes that make up sufficiently large fractions of the landscape. The regression F-statistic and the closely associated p-values are good indicators for this latter prerequisite and for other sources of uncertainty in the dis-aggregated flux estimates that render it meaningful or not. An analysis of the effect of various sources of errors in input data, footprint estimates and of skewed land cover class distributions is presented. A validation of flux estimates obtained through the dis-aggregation method against independent ground data proved satisfactorily. Recommendations for the use of the method are given as are suggestions for further development
    The international urban energy balance models comparison project: first results from phase 1
    Grimmond, C.S.B. ; Blackett, M. ; Best, M. ; Barlow, J. ; Baik, J. ; Belcher, S.E. ; Steeneveld, G.J. - \ 2010
    Journal of Applied Meteorology and Climatology 49 (2010)6. - ISSN 1558-8424 - p. 1268 - 1292.
    stedelijke gebieden - energiebalans - modellen - vergelijkingen - aardoppervlak - urban areas - energy balance - models - comparisons - land surface - submesoscale soil model - regular building arrays - global climate model - anthropogenic heat - boundary-layer - canopy model - 2 cities - parameterization scheme - roughness lengths - street canyons
    A large number of urban surface energy balance models now exist with different assumptions about the important features of the surface and exchange processes that need to be incorporated. To date, no comparison of these models has been conducted; in contrast, models for natural surfaces have been compared extensively as part of the Project for Intercomparison of Land Surface Parameterisation Schemes. Here, the methods and first results from an extensive international comparison of 33 models are presented. The aim of the comparison overall is to understand the complexity required to model energy and water exchanges in urban areas. The degree of complexity included in the models is outlined and impacts on model performance are discussed. During the comparison there have been significant developments in the models with resulting improvements in performance (root mean square error falling by up to two-thirds). Evaluation is based on a dataset containing net all-wave radiation, sensible heat and latent heat flux observations for an industrial area in Vancouver. The aim of the comparison is two-fold: to identify those modelling approaches that minimise the errors in the simulated fluxes of the urban energy balance and to determine the degree of model complexity required for accurate simulations. There is evidence that some classes of models perform better for individual fluxes but no model performs best or worst for all fluxes. In general, the simpler models perform as well as the more complex models based on all statistical measures. Generally the schemes have best overall capability to model net all wave radiation and least capability to model latent heat flux
    Evaluation of the Surface Energy Balance System (SEBS) applied to ASTER imagery with flux-measurements at the SPARC 2004 site (Barrac, Spain)
    Kwast, J. van der; Timmermans, W. ; Gieske, A. ; Su, Z. ; Olioso, A. ; Jia, L. ; Elbers, J.A. ; Karssenberg, D. ; Jong, S. de - \ 2009
    Hydrology and Earth System Sciences Discussions 6 (2009)1. - ISSN 1812-2108 - p. 1165 - 1196.
    evapotranspiratie - aardoppervlak - energiebalans - warmtestroming - remote sensing - evapotranspiration - land surface - energy balance - heat flow - remote sensing
    Accurate quantification of the amount and spatial variation of evapotranspiration is important in a wide range of disciplines. Remote sensing based surface energy balance models have been developed to estimate turbulent surface energy fluxes at different scales. The objective of this study is to evaluate the Surface Energy Balance System (SEBS) model on a landscape scale, using tower-based flux measurements at different land cover units during an overpass of the ASTER sensor over the SPARC 2004 experimental site in Barrax (Spain). Additionally, the effect of replacement of empirical roughness functions in the model by field estimates or literature values is investigated. Modelled fluxes correspond better with flux measurements over uniform land cover compared to cases where different land covers are mixed in the measurement footprint. Furthermore SEBS underestimates sensible heat flux, which is common in one source models
    EAGLE 2006 - Multi-purpose, multi-angle and multi-sensor in-situ and airborne campaigns over grassland and forest
    Su, Z. ; Timmermans, W.J. ; Tol, C. van der; Dost, R. ; Bianchi, R. ; Gómez, J.A. ; House, A. ; Hajnsek, I. ; Menenti, M. ; Magliulo, V. ; Esposito, M. ; Haarbrink, R. ; Bosveld, F. ; Moors, E.J. - \ 2009
    Hydrology and Earth System Sciences 13 (2009)6. - ISSN 1027-5606 - p. 833 - 845.
    hydrometeorologie - aardoppervlak - meettechnieken - remote sensing - meteorologische waarnemingen - hydrometeorology - land surface - measurement techniques - remote sensing - meteorological observations - energy
    EAGLE2006 ¿ an intensive field campaign for the advances in land surface hydrometeorological processes ¿ was carried out in the Netherlands from 8th to 18th June 2006, involving 16 institutions with in total 67 people from 16 different countries. In addition to the acquisition of multi-angle and multi-sensor satellite data, several airborne instruments ¿ an optical imaging sensor, an imaging microwave radiometer, and a flux airplane ¿ were deployed and extensive ground measurements were conducted over one grassland site at Cabauw and two forest sites at Loobos and Speulderbos in the central part of the Netherlands. The generated data set is both unique and urgently needed for the development and validation of models and inversion algorithms for quantitative land surface parameter estimation and land surface hydrometeorological process studies. EAGLE2006 was led by the Department of Water Resources of the International Institute for Geo-Information Science and Earth Observation (ITC) and originated from the combination of a number of initiatives supported by different funding agencies. The objectives of the EAGLE2006 campaign were closely related to the objectives of other European Space Agency (ESA) campaign activities (SPARC2004, SEN2FLEX2005 and especially AGRISAR2006). However, one important objective of the EAGLE2006 campaign is to build up a data base for the investigation and validation of the retrieval of bio-geophysical parameters, obtained at different radar frequencies (X-, C- and L-Band) and at hyperspectral optical and thermal bands acquired simultaneously over contrasting vegetated fields (forest and grassland). As such, all activities were related to algorithm development for future satellite missions such as the Sentinels and for validation of retrievals of land surface parameters with optical and thermal and microwave sensors onboard current and future satellite missions. This contribution describes the campaign objectives and provides an overview of the airborne and field campaign dataset. This dataset is available for scientific investigations and can be accessed on the ESA Principal Investigator Portal
    Effects of spatial variation in land cover on N2O emission of Dutch fen meadow systems
    Nol, L. ; Verburg, P.H. ; Heuvelink, G.B.M. - \ 2008
    ruimtelijke variatie - grondbeheer - emissie - stikstof - grondbedekking - aardoppervlak - spatial variation - land management - emission - nitrogen - ground cover - land surface
    Poster on effects of spatial variation in land cover on N2O emission of Dutch fen meadow systems
    Testing of modifications in the land surface scheme HTESSEL
    Wipfler, E.L. ; Metselaar, K. ; Dam, J.C. van; Feddes, R.A. ; Meijgaard, E. van; Hurk, B.J.J.M. van den; Zwart, S.J. ; Bastiaansen, W.G.M. - \ 2008
    klimaat - modellen - verandering - vochtigheid - bodem - lucht - aardoppervlak - climate - models - change - humidity - soil - air - land surface
    The land surface scheme HTESSEL has been revised including flexible numerical discretization, a soil depth according to the FAO soil map, a modification of root water uptake parameters, and the effect of shallow groundwater
    Definition of socioeconomic scenarios for land surface hydrology simulations of the 21st century
    Gerten, D. ; Haddeland, I. ; Hagemann, S. ; Ludwig, F. ; Wiberg, D. - \ 2008
    Wageningen : Watch (Technical Report / WATCH, Water and Global Change no. 5) - 4
    hydrologie - simulatie - sociale economie - aardoppervlak - hydrology - simulation - socioeconomics - land surface
    Quantification of land-atmosphere exchanges of water, energy and carbon dioxide in space and time over the heterogeneous Barrax site
    Su, Z. ; Timmermans, W. ; Gieske, A. ; Jia, L. ; Elbers, J.A. ; Olioso, A. ; Timmermans, J. ; Velde, R. van der; Jin, X. ; Kwast, H. van der; Nerry, F. ; Sabol, D. ; Sobrino, J.A. ; Moreno, J. ; Bianchi, R. - \ 2008
    International Journal of Remote Sensing 29 (2008)17-18. - ISSN 0143-1161 - p. 5215 - 5235.
    energie-uitwisseling - atmosfeer - aardoppervlak - water - kooldioxide - vegetatie - meting - atmosferische grenslaag - remote sensing - energy exchange - atmosphere - land surface - water - carbon dioxide - vegetation - measurement - atmospheric boundary-layer - remote sensing
    To advance our understanding of land-atmosphere exchanges of water, energy and carbon dioxide (CO2) in space and time over heterogeneous land surfaces, two intensive field campaigns were carried out at the Barrax agricultural test site in Spain during 12-21 July 2004 (SPARC 2004) and 8-14 July 2005 (SEN2FLEX 2005) involving multiple field, satellite and airborne instruments for characterizing the state of the atmosphere, the vegetation and the soil from the visible to the microwave range of the spectrum. Part of the experimental area is a core site of area 25 km2, within which numerous crops are grown, on both irrigated and dry land, alongside fields of bare soil. The campaigns were carried out in the framework of the Earth Observation Envelope Programme of the European Space Agency (ESA) with the aim of supporting geophysical algorithm development, calibration/validation and the simulation of future spaceborne Earth Observation missions. Both campaigns were also contributions to the EU 6FP EAGLE Project. The emphasis of this contribution is on the in situ measurements of land-atmosphere exchanges of water, energy and CO2 as well as the thermal dynamic states of the atmosphere, the soil and the vegetation. Preliminary analysis and interpretation of the measurements are presented. These two data sets are open to the scientific community for collaborative investigations.
    Towards closing the surface energy budget of a mid-latitude grassland
    Jacobs, A.F.G. ; Heusinkveld, B.G. ; Holtslag, A.A.M. - \ 2008
    Boundary-Layer Meteorology 126 (2008)1. - ISSN 0006-8314 - p. 125 - 136.
    energiebalans - graslanden - fotosynthese - aardoppervlak - warmtestroming - energy balance - grasslands - photosynthesis - land surface - heat flow - balance closure - heat-flux - eddy-correlation - boundary-layer - storage terms - forest - land - cases-99 - carbon - area
    Observations for May and August, 2005, from a long-term grassland meteorological station situated in central Netherlands were used to evaluate the closure of the surface energy budget. We compute all possible enthalpy changes, such as the grass cover heat storage, dew water heat storage, air mass heat storage and the photosynthesis energy flux, over an averaging time interval. In addition, the soil heat flux was estimated using a harmonic analysis technique to obtain a more accurate assessment of the surface soil heat flux. By doing so, a closure of 96% was obtained. The harmonic analysis technique appears to improve closure by 9%, the photosynthesis for 3% and the rest of the storage terms for a 3% improvement of the energy budget closure. For calm nights (friction velocity u * <0.1 m s¿1) when the eddy covariance technique is unreliable for measurement of the vertical turbulent fluxes, the inclusion of a scheme that calculates dew fluxes improves the energy budget closure significantly.
    Understanding and prediction of stable atmospheric boundary layers over land
    Steeneveld, G.J. - \ 2007
    Wageningen University. Promotor(en): Bert Holtslag, co-promotor(en): B.J.H. van de Wiel. - [S.l.] : S.n. - ISBN 9789085047162 - 199
    atmosfeer - klimaatfactoren - modellen - voorspelling - meteorologische factoren - grenslaagmeteorologie - aardoppervlak - atmosferische grenslaag - atmosphere - climatic factors - models - prediction - meteorological factors - boundary-layer meteorology - land surface - atmospheric boundary-layer
    The main objective of this thesis is to contribute to further understanding of the stable boundary layer (SBL) over land, and its representation in atmospheric models. A SBL develops during night due to radiative surface cooling. Observations in the SBL are difficult since many different physical processes can play a role. These processes are turbulent mixing, radiative transport, a coupling with the vegetation and underlying soil, drainage flows, gravity waves, fog, and aspects of land use heterogeneity. Therefore, the understanding and the representation of the SBL in weather forecast and climate models is relatively poor, especially for calm nights. In this thesis, a detailed column model of the atmosphere-land surface system is used to represent the atmospheric boundary layer over land and ice. As such, LES results and CASES99 field observations are used for comparison and model evaluation. It turns out that the degree of land-surface coupling plays a key role in forecasting the SBL. Also, the sensitivity of the radiation transfer model to vertical resolution is examined. It is found that the SBL can be satisfactorily modelled (except for the low-level jet (LLJ) and intermittency of the turbulence) if the geostrophic wind speed, advection, subsidence, and vegetation and soil properties are known, and if relatively high vertical resolution is used near the surface (both in the soil and in the atmosphere). The column model is used to study the nighttime 2m temperature increase due to additional CO2 as function of wind speed. Observations show that the temperature increase is similar for windy and calm nights, although this is somewhat counterintuitive. Model results confirm that the temperature increase is indeed similar for windy and calm nights. Next an intercomparison study of limited area weather forecast models (COAMPS, MM5, HIRLAM) is performed for CASES-99. Large errors occur in the forecasted minimum temperature, SBL height and diurnal temperature range. Models that account for a realistic interaction with the land surface are advantageous. A sufficient large domain is required to forecast the LLJ, and the forecasted surface cooling is very sensitive to the choice of the radiation scheme, especially for calm nights. Overall it is possible to upgrade the model performance by using the lessons learnt with the column model. In the thesis, also the role of orographic drag on the SBL is explored. It is shown that orography of 10 m amplitude can produce drag as large as the turbulent drag. Accounting for this in a model gave sufficient cyclone filling and a better forecast of the SBL structure and LLJ. The thesis concludes with studies of the SBL height. Dimensional analysis is used to derive a new and robust formulation for the SBL height for a broad range of latitude land-use conditions.
    Determination of regional surface heat fluxes over heterogeneous landscapes by integrating satellite remote sensing with boundary layer observations
    Ma, Y.M. - \ 2006
    Wageningen University. Promotor(en): Reinder Feddes; M. Menenti, co-promotor(en): J.M. Wang. - [S.l. ] : S.n. - ISBN 9789085044833 - 181
    warmtestroming - remote sensing - satellietkarteringen - meteorologische waarnemingen - atmosfeer - landschap - luchtstroming - warmteuitwisseling - grenslaag - aardoppervlak - heat flow - remote sensing - satellite surveys - meteorological observations - atmosphere - landscape - air flow - heat exchange - boundary layer - land surface
    Keywords: satellite remote sensing, surface layer observations, atmospheric boundary layer observations, land surface variables, vegetation variables, land surface heat fluxes, validation, heterogeneous landscape, GAME/Tibet, CAMP/Tibet, HEIFE, AECMP'95, DHEX, NOAA/AVHRR, Landsat-5(7) TM(ETM)  

    Arid areas such as theHeiheRiver Basinand high elevation areas as the Tibetan Plateau with a heterogeneous landscape are characterized by extreme gradients in land surface properties such as wetness and roughness which have a significant but local impact on the Atmospheric Boundary Layer (ABL). Observation of the actual extent of these areas and their properties is essential to understand the mechanisms through which heterogeneous land surfaces may have a significant impact on the structure and dynamics of the overlying ABL. The latter applies specifically to energy and water fluxes. Progress in this research area requires spatial measurements of variables such as surface hemispherical reflectance, radiometric surface temperature, vegetation fractional cover, Leaf Area Index ( LAI ) and local aerodynamic and thermodynamic roughness lengths. It also requires the measurements of Normalized Difference Vegetation Index ( NDVI ), Modified Soil Adjusted Vegetation Index ( MSAVI ). Imaging radiometers on-board satellites can provide useful estimates of most of these variables. Using these variables in combination with the Surface Layer (SL) and ABL observations we are able to derive the distribution of land surface heat fluxes over heterogeneous landscapes.

    Based on the analysis of the land surface heterogeneity and its effects on the overlying air flow, SL observations, ABL observations and satellite Remote Sensing (RS) measurements[Landsat-5(7) TM (ETM) and NOAA/AVHRR measurements], three parameterization methodologies,which are called RS approach (RS + SL-assumptions), Tile approach (RS + SL-observations) and Blending height approach (RS + SL-observations + ABL-observations) are developed and demonstrated to estimate the surface heat flux densities over heterogeneous landscapes. The RS approach (see Figures 3.4 and 5.1) uses satellite measurementsin combination with assumptions on the SL at and below a reference height of about2m.The Tile approach (see Figures 3.4, 3.5 and 7.1) uses satellite measurements in combination with SL observations at and below a reference height of about20m. The Blending height approach (see Figures 3.4, 3.6 and 7.2) uses satellite measurements in combination with SL and ABL observations at and below the blending height of about200m.

    The approaches were applied to heterogeneous areas: theHEIhe basin Field Experiment (HEIFE),the Arid Environment Comprehensive Monitoring Plan, 95 (AECMP'95), theGlobal Energy and Water cycle EXperiment Asian Monsoon Experiment on the Tibetan Plateau(GAME/Tibet), theCoordinated Enhanced Observing Period Asia-Australia Monsoon Project on the Tibetan Plateau(CAMP/Tibet) and the DunHuang EXperiment (DHEX). The distributions of NDVI , MSAVI , vegetation fractional cover, LAI , surface reflectance, surface temperature, net radiation flux, soil heat flux, sensible heat flux and latent heat flux have been determined over five different heterogeneous areas. These estimates have been compared with independent ground measurements of flux densities.At the validation sites relative deviations ( ) were less than 10 %. The results derived from the Blending height approach were also compared over the HEIFE area with that derived from the RS approach.

    The results clearly show that the Tile approach and the Blending height approachusing satellite measurements in combination with SL observationsand ABL observations provided much better estimates of heat flux densities than the RS approach.
    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.