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 

    Records 1 - 20 / 28

    • help
    • print

      Print search results

    • export

      Export search results

    Check title to add to marked list
    Turbulence vertical structure of the boundary layer during the afternoon transition
    Darbieu, C. ; Lohou, F. ; Lothon, M. ; Vilà-Guerau De Arellano, J. ; Couvreux, F. ; Durand, P. ; Pino, D. ; Patton, E.G. ; Nilsson, E. ; Blay-Carreras, E. ; Giolo, B. - \ 2015
    Atmospheric Chemistry and Physics 15 (2015). - ISSN 1680-7316 - p. 10071 - 10086.
    We investigate the decay of planetary boundary layer (PBL) turbulence in the afternoon, from the time the surface buoyancy flux starts to decrease until sunset. Dense observations of mean and turbulent parameters were acquired during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) field experiment by several meteorological surface stations, sounding balloons, radars, lidars and two aircraft during the afternoon transition. We analysed a case study based on some of these observations and largeeddy simulation (LES) data focusing on the turbulent vertical structure throughout the afternoon transition. The decay of turbulence is quantified through the temporal and vertical evolution of (1) the turbulence kinetic energy (TKE), (2) the characteristic length scales of turbulence and (3) the shape of the turbulence spectra. A spectral analysis of LES data, airborne and surface measurements is performed in order to characterize the variation in the turbulent decay with height and study the distribution of turbulence over eddy size. This study highlights the LES ability to reproduce the turbulence evolution throughout the afternoon. LESs and observations agree that the afternoon transition can be divided in two phases: (1) a first phase during which the TKE decays at a low rate, with no significant change in turbulence characteristics, and (2) a second phase characterized by a larger TKE decay rate and a change in spectral shape, implying an evolution of eddy size distribution and energy cascade from low to high wave number. The changes observed either in TKE decay (during the first phase) or in the vertical wind spectra shape (during the second phase of the afternoon transition) occur first in the upper region of the PBL. The higher within the PBL, the stronger the spectra shape changes.
    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.
    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.
    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.
    Quantifying the uncertainties of advection and boundary layer dynamics on the diurnal carbon dioxide budget
    Pino, D. ; Kaikkonen, J.P. ; Vilà-Guerau de Arellano, J. - \ 2013
    Journal of Geophysical Research: Atmospheres 118 (2013)16. - ISSN 2169-897X - p. 9376 - 9392.
    co2 mixing ratios - atmospheric co2 - regional-scale - error characterization - transport models - cabauw tower - tall tower - exchange - flux - entrainment
    [1] We investigate the uncertainties in the carbon dioxide (CO2) mixing ratio and inferred surface flux associated with boundary layer processes and advection by using mixed-layer theory. By extending the previous analysis presented by Pino et al. (2012), new analytical expressions are derived to quantify the uncertainty of CO2 mixing ratio or surface flux associated to, among others, boundary layer depth, early morning CO2 mixing ratio at the mixed layer or at the free atmosphere; or CO2 advection. We identify and calculate two sorts of uncertainties associated to the CO2 mixing ratio and surface flux: instantaneous and past (due to advection). The numerical experiments are guided and constrained by meteorological and CO2 observations taken at the Cabauw 213 m tower. We select 2 days (25 September 2003 and 12 March 2004) with a well-defined convective boundary layer but different CO2 advection contributions. Our sensitivity analysis shows that uncertainty of the CO2 advection in the boundary layer due to instantaneous uncertainties represents at 1600 LT on 12 March 2004 a contribution of 2¿ppm and 0.072 mg m-2s-1 in the uncertainty of the CO2 mixing ratio and inferred surface flux, respectively. Taking into account that the monthly averaged minimum CO2 surface flux for March 2004 was -0.55 mg m-2s-1, the error on the surface flux is on the order of 10%. By including CO2 advection in the analytical expressions, we demonstrate that the uncertainty of the CO2 mixing ratio or surface flux also depends on the past uncertainties of the boundary layer depth.
    Uncertainties in the CO2 buget associated to boundary layer dynamics and CO2-advection
    Kaikkonen, J.P. ; Pino, D. ; Vilà-Guerau de Arellano, J. - \ 2012
    In: 20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, American Meteorological Society (9-13 July 2012, Boston, MA). - Boston : American Meteorological Society - p. 9A.1 - 9A.1.
    The relationship between boundary layer dynamics and carbon dioxide (CO2) budget in the convective boundary layer (CBL) is investigated by using mixed-layer theory. We derive a new set of analytical relations to quantify the uncertainties on the estimation of the bulk CO2 mixing ratio and the inferred surface flux. This analysis of the uncertainties is done as a function of boundary layer depth, morning vertical CO2 distribution, which also includes the CO2 vertical gradient in the free atmosphere (FA) and the carbon dioxide horizontal advection. We apply these relations for two prototype convective boundary layers observed at the Cabauw tower in The Netherlands: one CBL is near the free convective regime and the other is largely influenced by advection of CO2. We find that at midday CO2 mixing ratio in the boundary layer and CO2-inferred surface flux are mainly sensitive to the early morning CO2 mixing ratio in the boundary layer and in the FA, just above the inversion. From the sensitivities the actual errors of CO2 mixing ratio and inferred surface flux are calculated by assuming typical errors on the variables considered. Notice that the contribution of the error of each analyzed variable on the CO2 budget depends on the sensitivity and on the uncertainty of the variable understudy. Consequently, although CO2 mixing ratio or the inferred surface flux have small sensitivity to some of the analyzed variables, errors in these variables can have a non-negligible contribution to the errors in the CO2 mixing ratio and in the inferred CO2 surface flux. This is the case of the CO2 vertical gradient in the FA. Focusing on the CO2 advection, we find that errors lead to notable uncertainties in the simulated CO2 mixing ratio even on diurnal time scales. This is due to the fact that these errors are of the order of the advection rates. This finding is very relevant since CO2-horizontal advection is a contribution to the CO2 budget characterized by large uncertainty in its quantification either by using measurements or modeling. Furthermore, CO2 mixing ratio errors due to advection are history dependent and hence even small systematic errors can increase to cause substantial errors in the CO2 mixing ratio. Similar conclusions can also be drawn regarding to the inferred CO2 surface flux. Our findings stress the fact that advection plays an important role on the CO2 budget even when diurnal time scales are studied. We complete the analysis of the uncertainties in the CO2 budget by studying the role of large-scale subsidence on the CO2-budget. We will show as an example that by introducing a deviation of approximately 1 cm/s in the subsidence velocity, we obtain differences of 4 ppm in the CO2 mixing ratio and 50% of the inferred CO2 surface flux. Consequently, not only horizontal but also vertical advection uncertainties, studied here as large-scale subsidence, lead to significant errors in the CO2 mixing ratio and in the inferred CO2 surface flux even on diurnal time scales.
    Role of residual layer and large-scale phenomena on the evolution of the boundary layer
    Blay, E. ; Pino, D. ; Vilà-Guerau de Arellano, J. ; Boer, A. van de; Coster, O. de; Faloona, I. ; Garrouste, O. ; Hartogensis, O.K. - \ 2012
    In: 20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, American Meteorological Society (9-13 July 2012, Boston, MA). - Boston : American Meteorological Society - p. 23 - 23.
    Mixed-layer theory and large-eddy simulations are used to analyze the dynamics of the boundary layer on two intensive operational periods during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) campaign: 1st and 2nd of July 2011, when convective boundary layers (CBLs) were observed. Continuous measurements made by several remote sensing and in situ instruments in combination with radiosoundings, and measurements done by unmanned aerial vehicles and an aircraft probed the vertical structure and the temporal evolution of the boundary layer. Mixed layer theory (Tennekes and Driedonks, 1981) and the Dutch Atmospheric Large-Eddy Simulation model (DALES, Heus et al., 2011) are set to reproduce and analyze the dynamics of the atmosphere during these two days. 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 model runs are inspired by the observations taken at the two supersites that concentrated most of the instrumentation during the campaign. For DALES the initial profile (at 7 UTC on 1st July and 5 UTC on 2nd July) takes into account the existence of a residual layer above the nocturnal stable layer observed during the early morning. The mixed layer model is initialized when a well-developed convective boundary layer was observed, from 10 UTC. Due to the surface heterogeneity of the area, the models were run separately to analyze the boundary layer conditions at the two different supersites. First, the research focuses on the role-played by the residual layer (RL) 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 to the development of the boundary layer at the morning. DALES, which takes into account the residual layer, is capable to model the observed sudden increase of the boundary layer depth and of the potential temperature occurred during the morning transition. There are different sources, which can be the responsible of the overshooting for instance surface and entrainment fluxes or large-scale phenomena. Analyzing the entrainment buoyancy heat flux, a large increase is obtained by the simulation when the residual layer is incorporated in the mixed layer by the growing convective boundary layer. Consequently, a precise definition of the characteristics of the residual layer is fundamental even though it is complex because the evolution of the main variables in the residual layer during the previous night depends on different factors such as radiation divergence or advection. Once the boundary layer is fully developed around midday, both models are used to study the dynamics of the boundary layer during the studied days. The models are able to reproduce the evolution of the boundary layer depth, potential temperature and specific humidity from late morning. They are also used to analyze the role played by subsidence and large-scale advection during the afternoon transition. During 1st of July, heat and moisture advection are negligible contributions to the heat or moisture budget, respectively, but subsidence plays an important role in the turbulence decay during the afternoon when a clear decrease of boundary layer depth was observed. On 2nd of July the main boundary layer variables follow similar evolution to the previous day, but with a lower maximum of the boundary layer depth. However, in the last part of the day, a front was approaching advecting moisture over the area and increasing the cloud cover. To summarize, the residual layer and large-scale phenomena play a crucial role in the development of the boundary layer during some days of the BLLAST campaign.
    Understanding and representing the effect of wind shear on the turbulent transfer in the convective boundary layer
    Ronda, R.J. ; Vilà-Guerau de Arellano, J. ; Pino, D. - \ 2012
    In: 20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, American Meteorological Society (9-13 July 2012, Boston, MA). - Boston : American Meteorological Society - p. 4.1A - 4.1A.
    Goal of this study is to quantify the effect of wind shear on the turbulent transport in the dry Convective Boundary Layer (CBL). Questions addressed include the effect of wind shear on the depth of the mixed layer, the effect of wind shear on the depth and structure of the capping inversion, and the effect of wind shear on the entrainment of free tropospheric air into the mixed layer. Following previous research, we use numerical experiments performed with the DALES LES-model varying both the strength and vertical profile of the geostrophic wind. In contrast to previous investigations, the effect of wind shear is analysed using a General Structure Model (GSM), instead of a more traditional zero-order or first order approach. We have selected the GSM framework because it allows for a more detailed assessment of the vertical structure of the capping inversion. Concepts derived within this framework can therefore be more easily transfered to global and meso-scale models turbulent transport parameterizations, as especially in conditions with high wind shear the capping inversion is often of such thickness that it can comprises multiple model layers in state-of-the art meso-scale and Numerical Weather Prediction (NWP) models. The effect of wind shear on the parameterized turbulence transport in NWP and meso-scale models is examined using the Eddy Diffusivity Mass-Flux (EDMF) approach. In contrast with traditional approaches based on K-theory, the EDMF framework acknowledges that turbulent transfer in the CBL can be decomposed into transport due to vertical advection by confined updrafts and diffusive transport (K-theory) within the updrafts and the environmental air. The DALES LES-model results are used to evaluate the effect of wind shear on the different parameters of the EDMF approach. Parameters include the release height and the excess temperature of a parcel that is employed to monitor the updrafts, the vertical velocity of an updraft parcel as it rises through the CBL and penetrates into the capping inversion, and the fraction of air occupied by the updrafts. This study thus extends previous research showing the performance of the EDMF approach in representing turbulent transfer in both clear and cloud-topped boundary layers without wind shear.
    On the role of large-scale forcings on the development of the atmospheric boundary layer during the BLLAST field campaign
    Pietersen, H.P. ; Vilà-Guerau de Arellano, J. ; Coster, O. de; Boer, A. van de; Hartogensis, O.K. ; Pino, D. ; Gioli, B. ; Durand, P. ; Lothon, M. ; Lohou, F. ; Reuder, J. ; Jonassen, M. ; Faloona, I. - \ 2012
    In: 20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, American Meteorological Society (9-13 July 2012, Boston, MA). - Boston : American Meteorological Society - p. 14B.2 - 14B.2.
    Guided and constrained by a complete data set of surface and upper-air observations taken during the fifth Intensive Observational Period (IOP-05, 25th June 2011) of the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) experiment, we reconstruct the evolution of the atmospheric boundary layer (ABL) using mixed-layer theory. The model results are corroborated by UHF radar and multiple profiles done by unmanned and manned aircraft platforms as well as by radiosondes. During the first morning hours, the ABL is mainly controlled by surface forcing, reaching a depth between 500 and 600 meter. At these levels, large-scale subsidence motions become similar in magnitude to the entrainment velocity and the ABL-growth becomes nearly zero. This equilibrium is maintained until the afternoon transition where mixed-layer model results and observations show a decrease of the boundary layer depth in spite of well mixed observed vertical profiles of heat and moisture. We discuss potential explanations to the development of subsidence motions associated to mesoscale flows driven by the proximity of the Pyrenees mountain range and to large-scale forcing. The heat and moisture budgets are also further analyzed with the mixed layer model. We find strong indications of the active role of heat and moisture advection required to reproduce the observed diurnal variability in temperature and specific humidity. By quantifying the budget terms, we are able to obtain a first estimation of the contribution of advection to the heat and moisture budgets. To complete the analysis, we extend the study to examine the turbulent characteristics of the ABL by using aircraft measurements combined with large-eddy simulations. In so doing, we are able to study the role of wind (directional) shear in the development and maintenance of the ABL. IOP05 was characterized by easterly flows within the ABL and westerly winds aloft. Our findings stress the important role of large scale forcing in understanding the ABL development at various stages during BLLAST. The proposed method can also be very useful to support the further interpretation of observations and mesoscale model experiments.
    The Boundary Layer Late Afternoon and Sunset Turbulence 2011 field experiment
    Lothon, M. ; Lohou, F. ; Durand, P. ; Couvreux, F. ; Hartogensis, O.K. ; Legain, D. ; Pardyjak, E. ; Pino, D. ; Vilà-Guerau de Arellano, J. ; Boer, A. van de; Moene, A.F. ; Steeneveld, G.J. - \ 2012
    In: 20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, American Meteorological Society (9-13 July 2012, Boston, MA). - Boston : American Meteorological Society - p. 14B.1 - 14B.1.
    BLLAST (Boundary Layer Late Afternoon and Sunset Turbulence) aims at better understanding the thermodynamical processes that occur during the late afternoon in the lower troposphere. In direct contact with the Earth surface, the atmospheric boundary layer is governed by buoyant and mechanical turbulence, with a strong diurnal cycle. The late afternoon transition, from the daytime dry convection to the night-time stable boundary layer, still raises a lot of issues and is poorly represented in the meteorological models. Yet, it plays an important role in the transport and diffusion of trace gases, like water vapour, carbon dioxide, pollutants, dusts... How does the afternoon decay in the lower troposphere happen, when the surface sensible heat flux start to sharply decrease ? How do the scales of the motions and transfers change ? What is the impact on the chemical closure and transport of trace gases and aerosols ? How to properly represent those processes in the meteorological models ? An international group is working on those issues by use of observations and numerical simulations, in order to improve our understanding and representation of the turbulent processes of the boundary-layer late afternoon transition. The roles of surface heterogeneity, entrainment at the boundary layer top, large scale subsidence, radiative effects, advection and gravity waves are studied. Due to the large lack of observations during this phase, a field campaign was organized in the vicinity of a 60-m instrumented tower of Laboratoire d'Aérologie, near the Pyrenees ridge in Southwest France, from 14 June to 8 July 2011. This experiment puts together complementary observation resources, in order to obtain an exhaustive description of the boundary-layer dynamical processes, its vertical structure, and the spatial variability related to surface heterogeneity. Continuous measurements (UHF radar and sodar wind profilers, lidars, ground stations), and intensive observations with aircraft, unmanned aerial vehicles, tethered balloons and radiosoundings were used. Particular emphasis was placed to bridge the different spatial scales with an integrated analysis of the observations and a complete numerical model hierarchy. This presentation will give an overview of the field experiment, with an emphasis on specific and innovative instrumental aspects, and with some preliminary results, introducing various contributions of BLLAST participants that will be shown along the 20th BLT conference.
    A conceptual framework to quantify the influence of convective boundary layer development on carbon dioxide mixing ratios
    Pino, D. ; Vilà-Guerau de Arellano, J. ; Peters, W. ; Schröter, J.S. ; Heerwaarden, C.C. van; Krol, M.C. - \ 2012
    Atmospheric Chemistry and Physics 12 (2012). - ISSN 1680-7316 - p. 2969 - 2985.
    atmospheric co2 - transport models - sensible heat - tall tower - exchange - fluxes - ecosystem - temperature - entrainment - variability
    Interpretation of observed diurnal carbon dioxide (CO2) mixing ratios near the surface requires knowledge of the local dynamics of the planetary boundary layer. In this paper, we study the relationship between the boundary layer dynamics and the CO2 budget in convective conditions through a newly derived set of analytical equations. From these equations, we are able to quantify how uncertainties in boundary layer dynamical variables or in the morning CO2 distribution in the mixed-layer or in the free atmosphere (FA) influence the bulk CO2 mixing ratio. We find that the largest uncertainty incurred on the midday CO2 mixing ratio comes from the prescribed early morning CO2 mixing ratios in the stable boundary layer, and in the free atmosphere. Errors in these values influence CO2 mixing ratios inversely proportional to the boundary layer depth (h), just like uncertainties in the assumed initial boundary layer depth and surface CO2 flux. The influence of uncertainties in the boundary layer depth itself is one order of magnitude smaller. If we “invert” the problem and calculate CO2 surface exchange from observed or simulated CO2 mixing ratios, the sensitivities to errors in boundary layer dynamics also invert: they become linearly proportional to the boundary layer depth. We demonstrate these relations for a typical well characterized situation at the Cabauw site in The Netherlands, and conclude that knowledge of the temperature and carbon dioxide profiles of the atmosphere in the early morning are of vital importance to correctly interpret observed CO2 mixing ratios during midday.
    Role of boundary layer processes on the mixed layer CO2-budget
    Pino, D. ; Vilà-Guerau de Arellano, J. - \ 2010
    In: 19th Symposium on Boundary Layers and Turbulence and the 29th Conference on Agricultural and Forest Meteorology; Keystone, Colorado, USA. - Boston : AMS - p. J9.1 - J9.1.
    The diurnal and vertical variability of temperature, humidity and specially CO2 in the atmospheric boundary layer is studied by combining detailed observations taken at Cabauw (The Netherlands), Large-Eddy simulations (LES) and mixed layer theory. The research focus on the role played by the entrainment and other boundary layer driven processes on the distribution and diurnal evolution of CO2 in the boundary layer. The relative importance of this entrained air to ventilate CO2 will be analyzed. During the morning the exchange of CO2 between the residual free tropospheric air masses with the growing boundary layer is a more important contribution than the CO2 uptake by the vegetation, whereas during the afternoon the assimilation by grass at the ground could become the dominant process. This work is completed by quantifying the terms of the budget conservation equation of CO2 using observations and the LES numerical experiments. It will be shown that under non-advective conditions, the flux divergence measurements can correctly reproduce the diurnal variability of temperature, moisture and CO2. The role of boundary layer dynamics on the CO2-budget has direct implications in inferring the CO2-uptake flux from CO2 observations. Our findings show how dynamic factors, as the morning temperature inversion or the lapse rate, are relevant in the retrieval of the CO2 flux. By analyzing the sensitivity of the inferred CO2 flux to the dynamics of the boundary layer and to the CO2 variables, we are able to estimate the uncertainties of the inferred CO2 flux to mean CO2 concentrations
    Studying the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST)
    Pino, D. ; Lothon, M. ; Angevine, W.M. ; Bange, J. ; Canut, G. ; Couvreux, F. ; Delbarre, H. ; Gibert, F. ; Vilà-Guerau de Arellano, J. - \ 2010
    Formulation of the Dutch Atmospheric Large-Eddy Simulation (DALES) and overview of its applications
    Heus, T. ; Heerwaarden, C.C. van; Jonker, H.J.J. ; Siebesma, A.P. ; Axelsen, S. ; Dries, C.L.A.M. van den; Geoffroy, O. ; Moene, A.F. ; Pino, D. ; Roode, S.R. de; Vilà-Guerau de Arellano, J. - \ 2010
    Geoscientific Model Development 3 (2010)2. - ISSN 1991-959X - p. 415 - 444.
    convective boundary-layer - shallow cumulus convection - characteristic length scales - topped mixed layers - liquid water path - aircraft observations - marine stratocumulus - radiative-transfer - simple parameterization - turbulent dispersion
    The current version of the Dutch Atmospheric Large-Eddy Simulation (DALES) is presented. DALES is a large-eddy simulation code designed for studies of the physics of the atmospheric boundary layer, including convective and stable boundary layers as well as cloudy boundary layers. In addition, DALES can be used for studies of more specific cases, such as flow over sloping or heterogeneous terrain, and dispersion of inert and chemically active species. This paper contains an extensive description of the physical and numerical formulation of the code, and gives an overview of its applications and accomplishments in recent years
    On inferring isoprene emission surface flux from atmospheric boundary layer concentration measurements
    Vilà-Guerau de Arellano, J. ; Dries, K. van den; Pino, D. - \ 2009
    Atmospheric Chemistry and Physics 9 (2009). - ISSN 1680-7316 - p. 3629 - 3640.
    model - hydrocarbons - entrainment - inversion - forest - parameterization - dynamics - cumulus - amazon - site
    We examine the dependence of the inferred isoprene surface emission flux from atmospheric concentration on the diurnal variability of the convective boundary layer (CBL). A series of systematic numerical experiments carried out using the mixed-layer technique enabled us to study the sensitivity of isoprene fluxes to the entrainment process, the partition of surface fluxes, the horizontal advection of warm/cold air masses and subsidence. Our findings demonstrate the key role played by the evolution of boundary layer height in modulating the retrieved isoprene flux. More specifically, inaccurate values of the potential temperature lapse rate lead to changes in the dilution capacity of the CBL and as a result the isoprene flux may be overestimated or underestimated by as much as 20%. The inferred emission flux estimated in the early morning hours is highly dependent on the accurate estimation of the discontinuity of the thermodynamic values between the residual layer and the rapidly forming CBL. Uncertainties associated with the partition of the sensible and latent heat flux also yield large deviations in the calculation of the isoprene surface flux. Similar results are obtained if we neglect the influence of warm or cold advection in the development of the CBL.We show that all the above-mentioned processes are non-linear, for which reason the dynamic and chemical evolutions of the CBL must be solved simultaneously. Based on the discussion of our results, we suggest the measurements needed to correctly apply the mixed-layer technique in order to minimize the uncertainties associated with the diurnal variability of the convective boundary layer.
    Scaling analysis of the turbulent kinetic energy at the entrainment zone in sheared convective boundary layers
    Pino, D. ; Vilà-Guerau de Arellano, J. - \ 2008
    In: 18th Symposium on Boundary Layers and Turbulence, Stockholm, Sweden, 9 - 13 June, 2008. - Boston : American Meteorological Society - p. 2.4 - 2.4.
    Effects of shear in the convective boundary layer: analysis of the turbulent kinetic energy budget
    Pino, D. ; Vilà-Guerau de Arellano, J. - \ 2008
    Acta Geophysica 56 (2008)1. - ISSN 1895-6572 - p. 167 - 193.
    large-eddy simulations - topped mixed layers - part ii - scalar fields - bulk models - order-jump - wind shear - entrainment - dynamics - inversion
    Effects of convective and mechanical turbulence at the entrainment zone are studied through the use of systematic Large-Eddy Simulation (LES) experiments. Five LES experiments with different shear characteristics in the quasi-steady barotropic boundary layer were conducted by increasing the value of the constant geostrophic wind by 5 m s-1 until the geostrophic wind was equal to 20 m s-1. The main result of this sensitivity analysis is that the convective boundary layer deepens with increasing wind speed due to the enhancement of the entrainment heat flux by the presence of shear. Regarding the evolution of the turbulence kinetic energy (TKE) budget for the studied cases, the following conclusions are drawn: (i) dissipation increases with shear, (ii) the transport and pressure terms decrease with increasing shear and can become a destruction term at the entrainment zone, and (iii) the time tendency of TKE remains small in all analyzed cases. Convective and local scaling arguments are applied to parameterize the TKE budget terms. Depending on the physical properties of each TKE budget contribution, two types of scaling parameters have been identified. For the processes influenced by mixed-layer properties, boundary layer depth and convective velocity have been used as scaling variables. On the contrary, if the physical processes are restricted to the entrainment zone, the inversion layer depth, the modulus of the horizontal velocity jump and the momentum fluxes at the inversion appear to be the natural choices for scaling these processes. A good fit of the TKE budget terms is obtained with the scaling, especially for shear contribution.
    The role of atmospheric boundary layer processes in atmospheric chemistry
    Vilà-Guerau de Arellano, J. ; Jonker, H. ; Pino, D. ; Brink, H.M. ten; Chaumerliac, N. ; Faloona, I. ; Galmarini, S. ; Millán, M. ; Stutz, J. - \ 2007
    Bulletin of the American Meteorological Society 88 (2007)8. - ISSN 0003-0007 - p. 1245 - 1248.
    Role of Shear and the Inversion Strength During Sunset Turbulence Over Land: Characteristic Length Scales, pre print
    Pino, D. ; Jonker, H.J.J. ; Vilà-Guerau de Arellano, J. ; Dosio, A. - \ 2006
    Boundary-Layer Meteorology 121 (2006)3. - ISSN 0006-8314 - p. 537 - 556.
    convective boundary-layer - large-eddy simulation - homogeneous isotropic turbulence - decay - transition - transport
    The role of shear and inversion strength on the decay of convective turbulence during sunset over land is systematically studied by means of large-eddy simulations. Different decay rates have been found for the vertical and horizontal velocity fluctuations, resulting in an increase of the anisotropy for all the studied cases. Entrainment, which persists during the decay process, favours the appearance of vertical upward movements associated with a conversion from kinetic to potential energy. Particular attention is paid to the evolution of the characteristic length scale of the various turbulent variables during this process. The length scale evolution is found to depend on the wind shear characteristics, but not on the strength of the inversion. In general the length scales of the variables grow during decay because small-scale fluctuations dissipate faster than large-scale fluctuations. Only the length scale of the vertical velocity component remains nearly constant during decay. Spectral analysis of the variance budgets shows that pressure correlations are responsible for fixing this length scale, effectively compensating the strong but oscillating influence of buoyancy. In the shear cases, after an initial period of growth, the length scales start to decrease once the buoyancy-generated variance has sufficiently subsided. Also here the effect of pressure redistribution is crucial, as it transfers the spectral influence of shear to the other velocity components
    Representing Sheared Convective Boundary Layer by Zeroth- and First-Order-Jump Mixed-Layer Models: Large-Eddy Simulation Verification
    Pino, D. ; Vilà-Guerau de Arellano, J. ; Kim, S.W. - \ 2006
    Journal of Applied Meteorology and Climatology 45 (2006)9. - ISSN 1558-8424 - p. 1224 - 1243.
    entrainment zone - wind shear - cumulus convection - kinetic-energy - part ii - inversion - growth - dynamics - parameterization - budget
    Dry convective boundary layers characterized by a significant wind shear on the surface and at the inversion are studied by means of the mixed-layer theory. Two different representations of the entrainment zone, each of which has a different closure of the entrainment heat flux, are considered. The simpler of the two is based on a sharp discontinuity at the inversion (zeroth-order jump), whereas the second one prescribes a finite depth of the inversion zone (first-order jump). Large-eddy simulation data are used to provide the initial conditions for the mixed-layer models, and to verify their results. Two different atmospheric boundary layers with different stratification in the free atmosphere are analyzed. It is shown that, despite the simplicity of the zeroth-order-jump model, it provides similar results to the first-order-jump model and can reproduce the evolution of the mixed-layer variables obtained by the large-eddy simulations in sheared convective boundary layers. The mixed-layer model with both closures compares better with the large-eddy simulation results in the atmospheric boundary layer characterized by a moderate wind shear and a weak temperature inversion. These results can be used to represent the flux of momentum, heat, and other scalars at the entrainment zone in general circulation or chemistry transport models.
    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.