Derivation of Structure Parameters of Temperature and Humidity in the Convective Boundary Layer from Large-Eddy Simulations and Implications for the Interpretation of Scintillometer Observations
Abstract:We derive the turbulent structure parameters of temperature C 2 T and humidity C 2 q from high-resolution large-eddy simulations (LES) of a homogeneously-heated convective boundary layer. Boundary conditions and model forcing were derived from measurements at Cabauw in The Netherlands. Three different methods to obtain the structure-parameters from LES are investigated. The shape of the vertical structure-parameter profiles from all three methods compare well with former experimental and LES results. Depending… Show more
“…For example, coherent structures in the convective ABL have been simulated by Raasch and Franke (2011) (dust devil-like vortices; see also visualization, Maronga et al, 2013a) and under neutral conditions at a forest edge by Kanani et al (2014c) and Kanani-Sühring and Raasch (2015) (using the canopy model). Classic vertical profiles of temperature, humidity, fluxes, structure parameters, and variances, as well as horizontal cross sections and turbulence spectra for the convective ABL, were shown, e.g., by Maronga and Raasch (2013) and Maronga et al (2013b). Moreover, Hellsten and Zilitinkevich (2013) used PALM to investigate the role of convective structures and background turbulence in the ABL.…”
Section: Past and Current Research Fieldsmentioning
confidence: 97%
“…Moreover, PALM has been applied to study the flow over Arctic ice leads and during cold-air outbreaks (e.g., Lüpkes et al, 2008;Gryschka et al, 2008Gryschka et al, , 2014. PALM has also been used several times to evaluate in situ measurement systems and strategies, e.g., for acoustic tomography, eddy covariance measurements, airborne flux observations, and scintillometers (e.g., Weinbrecht et al, 2004;Kanda et al, 2004;Sühring and Raasch, 2013;Maronga et al, 2013b). Steinfeld et al (2008), Markkanen et al (2010), and Sühring et al (2015) used the embedded LPM to determine accurate footprint estimations for tower and eddy covariance measurements.…”
Section: Past and Current Research Fieldsmentioning
Abstract. In this paper we present the current version of the Parallelized Large-Eddy Simulation Model (PALM) whose core has been developed at the Institute of Meteorology and Climatology at Leibniz Universität Hannover (Germany). PALM is a Fortran 95-based code with some Fortran 2003 extensions and has been applied for the simulation of a variety of atmospheric and oceanic boundary layers for more than 15 years. PALM is optimized for use on massively parallel computer architectures and was recently ported to general-purpose graphics processing units. In the present paper we give a detailed description of the current version of the model and its features, such as an embedded Lagrangian cloud model and the possibility to use Cartesian topography. Moreover, we discuss recent model developments and future perspectives for LES applications.
“…For example, coherent structures in the convective ABL have been simulated by Raasch and Franke (2011) (dust devil-like vortices; see also visualization, Maronga et al, 2013a) and under neutral conditions at a forest edge by Kanani et al (2014c) and Kanani-Sühring and Raasch (2015) (using the canopy model). Classic vertical profiles of temperature, humidity, fluxes, structure parameters, and variances, as well as horizontal cross sections and turbulence spectra for the convective ABL, were shown, e.g., by Maronga and Raasch (2013) and Maronga et al (2013b). Moreover, Hellsten and Zilitinkevich (2013) used PALM to investigate the role of convective structures and background turbulence in the ABL.…”
Section: Past and Current Research Fieldsmentioning
confidence: 97%
“…Moreover, PALM has been applied to study the flow over Arctic ice leads and during cold-air outbreaks (e.g., Lüpkes et al, 2008;Gryschka et al, 2008Gryschka et al, , 2014. PALM has also been used several times to evaluate in situ measurement systems and strategies, e.g., for acoustic tomography, eddy covariance measurements, airborne flux observations, and scintillometers (e.g., Weinbrecht et al, 2004;Kanda et al, 2004;Sühring and Raasch, 2013;Maronga et al, 2013b). Steinfeld et al (2008), Markkanen et al (2010), and Sühring et al (2015) used the embedded LPM to determine accurate footprint estimations for tower and eddy covariance measurements.…”
Section: Past and Current Research Fieldsmentioning
Abstract. In this paper we present the current version of the Parallelized Large-Eddy Simulation Model (PALM) whose core has been developed at the Institute of Meteorology and Climatology at Leibniz Universität Hannover (Germany). PALM is a Fortran 95-based code with some Fortran 2003 extensions and has been applied for the simulation of a variety of atmospheric and oceanic boundary layers for more than 15 years. PALM is optimized for use on massively parallel computer architectures and was recently ported to general-purpose graphics processing units. In the present paper we give a detailed description of the current version of the model and its features, such as an embedded Lagrangian cloud model and the possibility to use Cartesian topography. Moreover, we discuss recent model developments and future perspectives for LES applications.
“…The respective dissipation rate is denoted by and is computed as described in Maronga et al . []. One more possibility to estimate the TKE dissipation rate is to take it to be equal to the sum of all other TKE budget terms, that is …”
Section: Budgets Of Second‐order Momentsmentioning
confidence: 99%
“…Maronga et al . [] also found that the fall‐off of the spectrum in their simulations is intensified by numerical diffusion. The estimate (orange line) obtained with the residual method agrees well (both in terms of the magnitude and the shape of the vertical profile) with the TKE dissipation rate computed by M00.…”
Section: Budgets Of Second‐order Momentsmentioning
A detailed analysis of second-order moment budgets for cloud topped boundary layers (CTBLs) is performed using high-resolution large-eddy simulation (LES). Two CTBLs are simulated-one with trade wind shallow cumuli, and the other with nocturnal marine stratocumuli. Approximations to the ensemble-mean budgets of the Reynolds-stress components, of the fluxes of two quasi-conservative scalars, and of the scalar variances and covariance are computed by averaging the LES data over horizontal planes and over several hundred time steps. Importantly, the subgrid scale contributions to the budget terms are accounted for. Analysis of the LES-based second-moment budgets reveals, among other things, a paramount importance of the pressure scrambling terms in the Reynolds-stress and scalar-flux budgets. The pressure-strain correlation tends to evenly redistribute kinetic energy between the components, leading to the growth of horizontal-velocity variances at the expense of the verticalvelocity variance which is produced by buoyancy over most of both CTBLs. The pressure gradient-scalar covariances are the major sink terms in the budgets of scalar fluxes. The third-order transport proves to be of secondary importance in the scalar-flux budgets. However, it plays a key role in maintaining budgets of TKE and of the scalar variances and covariance. Results from the second-moment budget analysis suggest that the accuracy of description of the CTBL structure within the second-order closure framework strongly depends on the fidelity of parameterizations of the pressure scrambling terms in the flux budgets and of the third-order transport terms in the variance budgets.
“…Aside from using measurements from in situ or remote sensing instruments, C 2 T has also been examined through numerical simulation. The advancement of the large-eddy simulation (LES) technique has provided a tool to examine structure-function parameters of atmospheric flow in four dimensions both from LES data (Peltier and Wyngaard 1995;Cheinet and Cumin 2011;Wilson and Fedorovich 2012;Maronga et al 2013), and through the development of the LES-based numerical radar simulators (Muschinski et al 1999;Scipión et al 2008). One advantage of using LES data for this purpose is that both the spatial and temporal variability of C 2 T can be examined across a range of scales and also in relation to the separation-distance dependence.…”
Small-scale turbulent fluctuations of temperature are known to affect the propagation of both electromagnetic and acoustic waves. Within the inertial-subrange scale, where the turbulence is locally homogeneous and isotropic, these temperature perturbations can be described, in a statistical sense, using the structure-function parameter for temperature, C 2 T . Here we investigate different methods of evaluating C 2 T , using data from a numerical large-eddy simulation together with atmospheric observations collected by an unmanned aerial system and a sodar. An example case using data from a late afternoon unmanned aerial system flight on April 24 2013 and corresponding large-eddy simulation data is presented and discussed.
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