Sunset decay of the convective turbulence with Large-Eddy Simulation under realistic conditions

Rizza, Umberto; Miglietta, Mario Marcello; Degrazia, Gervásio Annes; Acevedo, Otávio C.; Filho, Edson Pereira Marques

doi:10.1016/j.physa.2013.05.009

Cited by 30 publications

(28 citation statements)

References 26 publications

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“…The two stages of the TKE decay found in this study remain consistent with previous results found by Nadeau et al (2011) and Rizza et al (2013a). Both authors showed a decrease in the TKE following a t −n power law with a continuous increase in n. Nadeau et al (2011) defined two main stages characterized by n around 2 and 6.…”

Section: Discussionsupporting

confidence: 92%

“…Both authors showed a decrease in the TKE following a t −n power law with a continuous increase in n. Nadeau et al (2011) defined two main stages characterized by n around 2 and 6. Rizza et al (2013a) added a preliminary stage with n equal to 1. Our first stage includes t −1 and t −2 power laws, and the second one includes t −6 .…”

Section: Discussionmentioning

confidence: 99%

“…Monin and Yaglom, 1975;Cole and Fernando, 1998), theoretical models (Goulart et al, 2003), numerical studies with large-eddy simulations (LESs) (e.g. Nieuwstadt and Brost, 1986;Sorbjan, 1997;Rizza et al, 2013a) and observations (e.g. Fitzjarrald et al, 2004;Grant, 1997;Brazel et al, 2005;Fernando et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

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Turbulence vertical structure of the boundary layer during the afternoon transition

et al. 2015

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Abstract.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.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

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Turbulence vertical structure of the boundary layer during the afternoon transition

et al. 2015

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“…Also Nadeau et al (2011) were able to model the decay observed in the surface layer with a model based on a mixed-layer parameterization, rather than on a surface-based parameterization. Based on the CASES-99 data set, Rizza et al (2013) performed a LES study of the decay phase whose results corroborate the findings of Nadeau et al (2011).…”

Section: Turbulence Kinetic Energy (Tke) Decaysupporting

confidence: 61%

The BLLAST field experiment: Boundary-Layer Late Afternoon and Sunset Turbulence

Lothon¹,

Pino²,

Couvreux³

et al. 2014

Atmos. Chem. Phys.

178

226

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Abstract. 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 tetheredballoon 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.

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“…See also discussions in Fedorovich and Conzemius (2008). In addition, Kumar et al (2006) and Rizza et al (2013) conducted LES of the diurnal cycle, whereas van Driel and Jonker (2011) carried out an idealized study and analysis of periodically varying surface heat flux and its impact on boundary layer height and TKE.…”

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confidence: 99%

Turbulence kinetic energy budget during the afternoon transition – Part 1: Observed surface TKE budget and boundary layer description for 10 intensive observation period days

et al. 2016

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Abstract. The decay of turbulence kinetic energy (TKE) and its budget in the afternoon period from midday until zerobuoyancy flux at the surface is studied in a two-part paper by means of measurements from the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) field campaign for 10 intensive observation period days. Here, in Part 1, near-surface measurements from a small tower are used to estimate a TKE budget. The overall boundary layer characteristics and mesoscale situation at the site are also described based upon taller tower measurements, radiosoundings and remote sensing instrumentation. Analysis of the TKE budget during the afternoon transition reveals a variety of different surface layer dynamics in terms of TKE and TKE decay. This is largely attributed to variations in the 8 m wind speed, which is responsible for different amounts of nearsurface shear production on different afternoons and variations within some of the afternoon periods. The partitioning of near-surface production into local dissipation and transport in neutral and unstably stratified conditions was investigated. Although variations exist both between and within afternoons, as a rule of thumb, our results suggest that about 50 % of the near-surface production of TKE is compensated for by local dissipation near the surface, leaving about 50 % available for transport. This result indicates that it is important to also consider TKE transport as a factor influencing the near-surface TKE decay rate, which in many earlier studies has mainly been linked with the production terms of TKE by buoyancy and wind shear. We also conclude that the TKE tendency is smaller than the other budget terms, indicating a quasi-stationary evolution of TKE in the afternoon transition. Even though the TKE tendency was observed to be small, a strong correlation to mean buoyancy production of −0.69 was found for the afternoon period. For comparison with previous results, the TKE budget terms are normalized with friction velocity and measurement height and discussed in the framework of Monin-Obukhov similarity theory. Empirically fitted expressions are presented. Alternatively, we also suggest a non-local parametrization of dissipation using a TKE-length scale model which takes into account the boundary layer depth in addition to distance above the ground. The non-local formulation is shown to give a better description of dissipation compared to a local parametrization.

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Sunset decay of the convective turbulence with Large-Eddy Simulation under realistic conditions

Cited by 30 publications

References 26 publications

Turbulence vertical structure of the boundary layer during the afternoon transition

Turbulence vertical structure of the boundary layer during the afternoon transition

The BLLAST field experiment: Boundary-Layer Late Afternoon and Sunset Turbulence

Turbulence kinetic energy budget during the afternoon transition – Part 1: Observed surface TKE budget and boundary layer description for 10 intensive observation period days

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