A Lumped Parameter View on Nocturnal Boundary Layer Dynamics

B.J.H. van de Wiel, I.G.S. Hooijdonk, E. Vignon, P. Baas, J.A. van Hooft, S.J. van der Linden, A.F. Moene

Research output: Contribution to conferenceConference paperAcademicpeer-review

Abstract

In clear nights a sudden change in turbulence characteristics may occur when the strength of the ambient wind drops below a certain threshold. This threshold is known as the ‘minimum wind speed for sustainable turbulence'. The near-surface inversion strength may rapidly increase resulting in the so-called very stable boundary layer (VSBL). In previous work by the authors, the mechanism behind this regime shift has been explained from a concept called the Maximum Sustainable Heat Flux theory and an expression for the minimum wind speed, Umin, in terms of the net radiative forcing at the surface was given.
The theory, however, made no statement about what happens after the regime shift has been established, i.e. after the VSBL has set in. In other words what happens to the surface energy balance and to the near surface inversion strength when turbulence becomes very weak? As ‘run-away cooling' is not occurring in nature, other thermodynamic processes have to take over.

Here, we aim to answer this question by extending the previous work, through introduction of simple surface feedbacks to the existing concepts. A so-called lumped parameter is introduced which account for the soil/radiative feedbacks in the conceptual model system. For an isolating surface (snow) this parameter has a lower value than over e.g. bare soil, which implies that the soil–feedback is weaker in the first case. As such the VSBL reaches much colder temperatures at equilibrium. Finally, we explore two observational sites with contrasting surface characteristics (Cabauw, Dome C) and interpret the observed characteristics with the new, lumped parameter model.
Original languageEnglish
Pages2A.2
Publication statusPublished - 2016
Event22th Symposium on Boundary Layers and Turbulence - Salt Lake City , United States
Duration: 22 Jun 201624 Jun 2016
https://ams.confex.com/ams/32AgF22BLT3BG/webprogram/Paper295983.html

Conference

Conference22th Symposium on Boundary Layers and Turbulence
CountryUnited States
CitySalt Lake City
Period22/06/1624/06/16
Internet address

Fingerprint

nocturnal boundary layer
boundary layer
turbulence
wind velocity
radiative forcing
bare soil
surface energy
energy balance
dome
heat flux
parameter
snow
thermodynamics
cooling

Cite this

van de Wiel, B. J. H., Hooijdonk, I. G. S., Vignon, E., Baas, P., van Hooft, J. A., van der Linden, S. J., & Moene, A. F. (2016). A Lumped Parameter View on Nocturnal Boundary Layer Dynamics. 2A.2. Paper presented at 22th Symposium on Boundary Layers and Turbulence, Salt Lake City , United States.
van de Wiel, B.J.H. ; Hooijdonk, I.G.S. ; Vignon, E. ; Baas, P. ; van Hooft, J.A. ; van der Linden, S.J. ; Moene, A.F. / A Lumped Parameter View on Nocturnal Boundary Layer Dynamics. Paper presented at 22th Symposium on Boundary Layers and Turbulence, Salt Lake City , United States.
@conference{1db910f5bd594e48ba430fb007bbdef6,
title = "A Lumped Parameter View on Nocturnal Boundary Layer Dynamics",
abstract = "In clear nights a sudden change in turbulence characteristics may occur when the strength of the ambient wind drops below a certain threshold. This threshold is known as the ‘minimum wind speed for sustainable turbulence'. The near-surface inversion strength may rapidly increase resulting in the so-called very stable boundary layer (VSBL). In previous work by the authors, the mechanism behind this regime shift has been explained from a concept called the Maximum Sustainable Heat Flux theory and an expression for the minimum wind speed, Umin, in terms of the net radiative forcing at the surface was given. The theory, however, made no statement about what happens after the regime shift has been established, i.e. after the VSBL has set in. In other words what happens to the surface energy balance and to the near surface inversion strength when turbulence becomes very weak? As ‘run-away cooling' is not occurring in nature, other thermodynamic processes have to take over. Here, we aim to answer this question by extending the previous work, through introduction of simple surface feedbacks to the existing concepts. A so-called lumped parameter is introduced which account for the soil/radiative feedbacks in the conceptual model system. For an isolating surface (snow) this parameter has a lower value than over e.g. bare soil, which implies that the soil–feedback is weaker in the first case. As such the VSBL reaches much colder temperatures at equilibrium. Finally, we explore two observational sites with contrasting surface characteristics (Cabauw, Dome C) and interpret the observed characteristics with the new, lumped parameter model.",
author = "{van de Wiel}, B.J.H. and I.G.S. Hooijdonk and E. Vignon and P. Baas and {van Hooft}, J.A. and {van der Linden}, S.J. and A.F. Moene",
year = "2016",
language = "English",
pages = "2A.2",
note = "22th Symposium on Boundary Layers and Turbulence ; Conference date: 22-06-2016 Through 24-06-2016",
url = "https://ams.confex.com/ams/32AgF22BLT3BG/webprogram/Paper295983.html",

}

van de Wiel, BJH, Hooijdonk, IGS, Vignon, E, Baas, P, van Hooft, JA, van der Linden, SJ & Moene, AF 2016, 'A Lumped Parameter View on Nocturnal Boundary Layer Dynamics' Paper presented at 22th Symposium on Boundary Layers and Turbulence, Salt Lake City , United States, 22/06/16 - 24/06/16, pp. 2A.2.

A Lumped Parameter View on Nocturnal Boundary Layer Dynamics. / van de Wiel, B.J.H.; Hooijdonk, I.G.S.; Vignon, E.; Baas, P.; van Hooft, J.A. ; van der Linden, S.J.; Moene, A.F.

2016. 2A.2 Paper presented at 22th Symposium on Boundary Layers and Turbulence, Salt Lake City , United States.

Research output: Contribution to conferenceConference paperAcademicpeer-review

TY - CONF

T1 - A Lumped Parameter View on Nocturnal Boundary Layer Dynamics

AU - van de Wiel, B.J.H.

AU - Hooijdonk, I.G.S.

AU - Vignon, E.

AU - Baas, P.

AU - van Hooft, J.A.

AU - van der Linden, S.J.

AU - Moene, A.F.

PY - 2016

Y1 - 2016

N2 - In clear nights a sudden change in turbulence characteristics may occur when the strength of the ambient wind drops below a certain threshold. This threshold is known as the ‘minimum wind speed for sustainable turbulence'. The near-surface inversion strength may rapidly increase resulting in the so-called very stable boundary layer (VSBL). In previous work by the authors, the mechanism behind this regime shift has been explained from a concept called the Maximum Sustainable Heat Flux theory and an expression for the minimum wind speed, Umin, in terms of the net radiative forcing at the surface was given. The theory, however, made no statement about what happens after the regime shift has been established, i.e. after the VSBL has set in. In other words what happens to the surface energy balance and to the near surface inversion strength when turbulence becomes very weak? As ‘run-away cooling' is not occurring in nature, other thermodynamic processes have to take over. Here, we aim to answer this question by extending the previous work, through introduction of simple surface feedbacks to the existing concepts. A so-called lumped parameter is introduced which account for the soil/radiative feedbacks in the conceptual model system. For an isolating surface (snow) this parameter has a lower value than over e.g. bare soil, which implies that the soil–feedback is weaker in the first case. As such the VSBL reaches much colder temperatures at equilibrium. Finally, we explore two observational sites with contrasting surface characteristics (Cabauw, Dome C) and interpret the observed characteristics with the new, lumped parameter model.

AB - In clear nights a sudden change in turbulence characteristics may occur when the strength of the ambient wind drops below a certain threshold. This threshold is known as the ‘minimum wind speed for sustainable turbulence'. The near-surface inversion strength may rapidly increase resulting in the so-called very stable boundary layer (VSBL). In previous work by the authors, the mechanism behind this regime shift has been explained from a concept called the Maximum Sustainable Heat Flux theory and an expression for the minimum wind speed, Umin, in terms of the net radiative forcing at the surface was given. The theory, however, made no statement about what happens after the regime shift has been established, i.e. after the VSBL has set in. In other words what happens to the surface energy balance and to the near surface inversion strength when turbulence becomes very weak? As ‘run-away cooling' is not occurring in nature, other thermodynamic processes have to take over. Here, we aim to answer this question by extending the previous work, through introduction of simple surface feedbacks to the existing concepts. A so-called lumped parameter is introduced which account for the soil/radiative feedbacks in the conceptual model system. For an isolating surface (snow) this parameter has a lower value than over e.g. bare soil, which implies that the soil–feedback is weaker in the first case. As such the VSBL reaches much colder temperatures at equilibrium. Finally, we explore two observational sites with contrasting surface characteristics (Cabauw, Dome C) and interpret the observed characteristics with the new, lumped parameter model.

M3 - Conference paper

SP - 2A.2

ER -

van de Wiel BJH, Hooijdonk IGS, Vignon E, Baas P, van Hooft JA, van der Linden SJ et al. A Lumped Parameter View on Nocturnal Boundary Layer Dynamics. 2016. Paper presented at 22th Symposium on Boundary Layers and Turbulence, Salt Lake City , United States.