Details
| Original language | English |
|---|---|
| Pages (from-to) | 79-97 |
| Number of pages | 19 |
| Journal | Boundary-Layer Meteorology |
| Volume | 173 |
| Issue number | 1 |
| Early online date | 12 Jun 2019 |
| Publication status | Published - Oct 2019 |
Abstract
We investigate the scaling for decaying turbulence kinetic energy (TKE) in the free-convective boundary layer, from the time the surface heat flux starts decaying, until a few hours after it has vanished. We conduct a set of large-eddy simulation experiments, consider various initial convective situations, and prescribe realistic decays of the surface heat flux over a wide range of time scales. We find that the TKE time evolution is dictated by the decaying magnitude of the surface heat flux up to 0.7 τ approximately, where τ is the prescribed duration from maximum to zero surface heat flux. During the time period starting at zero surface heat flux, we search for potential power-law scaling by examining the log–log presentation of TKE as a function of time. First, we find that the description of the decay highly depends on whether the time origin is defined as the time when the surface heat flux starts decaying (traditional scaling framework), or the time when it vanishes (proposed new scaling framework). Second, when varying τ, the results plotted in the traditional scaling framework indicate variations in the power-law decay rates over several orders of magnitude. In the new scaling framework, however, we find a unique decay exponent in the order of 1, independent of the initial convective condition, and independent of τ, giving support for the proposed scaling framework.
Keywords
- Convective scaling, Free-convective boundary layer, Power-law scaling, Similarity relations, Turbulence kinetic energy decay
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Atmospheric Science
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In: Boundary-Layer Meteorology, Vol. 173, No. 1, 10.2019, p. 79-97.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Scaling the Decay of Turbulence Kinetic Energy in the Free-Convective Boundary Layer
AU - El Guernaoui, Omar
AU - Reuder, Joachim
AU - Esau, Igor
AU - Wolf, Tobias
AU - Maronga, Björn
N1 - Funding Information: We wish to thank the two anonymous reviewers for their helpful and constructive comments. CPU time was provided through the Norwegian Supercomputing Project NOTUR (II) Grant Nos. NN9528k and NN9506k.
PY - 2019/10
Y1 - 2019/10
N2 - We investigate the scaling for decaying turbulence kinetic energy (TKE) in the free-convective boundary layer, from the time the surface heat flux starts decaying, until a few hours after it has vanished. We conduct a set of large-eddy simulation experiments, consider various initial convective situations, and prescribe realistic decays of the surface heat flux over a wide range of time scales. We find that the TKE time evolution is dictated by the decaying magnitude of the surface heat flux up to 0.7 τ approximately, where τ is the prescribed duration from maximum to zero surface heat flux. During the time period starting at zero surface heat flux, we search for potential power-law scaling by examining the log–log presentation of TKE as a function of time. First, we find that the description of the decay highly depends on whether the time origin is defined as the time when the surface heat flux starts decaying (traditional scaling framework), or the time when it vanishes (proposed new scaling framework). Second, when varying τ, the results plotted in the traditional scaling framework indicate variations in the power-law decay rates over several orders of magnitude. In the new scaling framework, however, we find a unique decay exponent in the order of 1, independent of the initial convective condition, and independent of τ, giving support for the proposed scaling framework.
AB - We investigate the scaling for decaying turbulence kinetic energy (TKE) in the free-convective boundary layer, from the time the surface heat flux starts decaying, until a few hours after it has vanished. We conduct a set of large-eddy simulation experiments, consider various initial convective situations, and prescribe realistic decays of the surface heat flux over a wide range of time scales. We find that the TKE time evolution is dictated by the decaying magnitude of the surface heat flux up to 0.7 τ approximately, where τ is the prescribed duration from maximum to zero surface heat flux. During the time period starting at zero surface heat flux, we search for potential power-law scaling by examining the log–log presentation of TKE as a function of time. First, we find that the description of the decay highly depends on whether the time origin is defined as the time when the surface heat flux starts decaying (traditional scaling framework), or the time when it vanishes (proposed new scaling framework). Second, when varying τ, the results plotted in the traditional scaling framework indicate variations in the power-law decay rates over several orders of magnitude. In the new scaling framework, however, we find a unique decay exponent in the order of 1, independent of the initial convective condition, and independent of τ, giving support for the proposed scaling framework.
KW - Convective scaling
KW - Free-convective boundary layer
KW - Power-law scaling
KW - Similarity relations
KW - Turbulence kinetic energy decay
UR - http://www.scopus.com/inward/record.url?scp=85067665226&partnerID=8YFLogxK
U2 - 10.1007/s10546-019-00458-z
DO - 10.1007/s10546-019-00458-z
M3 - Article
AN - SCOPUS:85067665226
VL - 173
SP - 79
EP - 97
JO - Boundary-Layer Meteorology
JF - Boundary-Layer Meteorology
SN - 0006-8314
IS - 1
ER -