Details
| Original language | English |
|---|---|
| Pages (from-to) | 441-470 |
| Number of pages | 30 |
| Journal | Boundary-Layer Meteorology |
| Volume | 153 |
| Issue number | 3 |
| Publication status | Published - 27 Aug 2014 |
Abstract
We conduct a high-resolution large-eddy simulation (LES) case study in order to investigate the effects of surface heterogeneity on the (local) structure parameters of potential temperature CT 2 and specific humidity Cq 2 in the convective boundary layer (CBL). The kilometre-scale heterogeneous land-use distribution as observed during the LITFASS-2003 experiment was prescribed at the surface of the LES model in order to simulate a realistic CBL development from the early morning until early afternoon. The surface patches are irregularly distributed and represent different land-use types that exhibit different roughness conditions as well as near-surface fluxes of sensible and latent heat. In the analysis, particular attention is given to the Monin–Obukhov similarity theory (MOST) relationships and local free convection (LFC) scaling for structure parameters in the surface layer, relating CT 2 and Cq 2 to the surface fluxes of sensible and latent heat, respectively. Moreover we study possible effects of surface heterogeneity on scintillometer measurements that are usually performed in the surface layer. The LES data show that the local structure parameters reflect the surface heterogeneity pattern up to heights of 100–200 m. The assumption of a blending height, i.e. the height above the surface where the surface heterogeneity pattern is no longer visible in the structure parameters, is studied by means of a two-dimensional correlation analysis. We show that no such blending height is found at typical heights of scintillometer measurements for the studied case. Moreover, Cq 2 does not follow MOST, which is ascribed to the entrainment of dry air at the top of the boundary layer. The application of MOST and LFC scaling to elevated CT 2 data still gives reliable estimates of the surface sensible heat flux. We show, however, that this flux, derived from scintillometer data, is only representative of the footprint area of the scintillometer, whose size depends strongly on the synoptic conditions.
Keywords
- Convective boundary layer, Large-eddy simulation, Scintillometry, Surface heterogeneity, Turbulent structure parameter
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Atmospheric Science
Sustainable Development Goals
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In: Boundary-Layer Meteorology, Vol. 153, No. 3, 27.08.2014, p. 441-470.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - The Effect of Surface Heterogeneity on the Structure Parameters of Temperature and Specific Humidity
T2 - A Large-Eddy Simulation Case Study for the LITFASS-2003 Experiment
AU - Maronga, Björn
AU - Hartogensis, Oscar K.
AU - Raasch, Siegfried
AU - Beyrich, Frank
N1 - Publisher Copyright: © 2014, The Author(s). Copyright: Copyright 2017 Elsevier B.V., All rights reserved.
PY - 2014/8/27
Y1 - 2014/8/27
N2 - We conduct a high-resolution large-eddy simulation (LES) case study in order to investigate the effects of surface heterogeneity on the (local) structure parameters of potential temperature CT 2 and specific humidity Cq 2 in the convective boundary layer (CBL). The kilometre-scale heterogeneous land-use distribution as observed during the LITFASS-2003 experiment was prescribed at the surface of the LES model in order to simulate a realistic CBL development from the early morning until early afternoon. The surface patches are irregularly distributed and represent different land-use types that exhibit different roughness conditions as well as near-surface fluxes of sensible and latent heat. In the analysis, particular attention is given to the Monin–Obukhov similarity theory (MOST) relationships and local free convection (LFC) scaling for structure parameters in the surface layer, relating CT 2 and Cq 2 to the surface fluxes of sensible and latent heat, respectively. Moreover we study possible effects of surface heterogeneity on scintillometer measurements that are usually performed in the surface layer. The LES data show that the local structure parameters reflect the surface heterogeneity pattern up to heights of 100–200 m. The assumption of a blending height, i.e. the height above the surface where the surface heterogeneity pattern is no longer visible in the structure parameters, is studied by means of a two-dimensional correlation analysis. We show that no such blending height is found at typical heights of scintillometer measurements for the studied case. Moreover, Cq 2 does not follow MOST, which is ascribed to the entrainment of dry air at the top of the boundary layer. The application of MOST and LFC scaling to elevated CT 2 data still gives reliable estimates of the surface sensible heat flux. We show, however, that this flux, derived from scintillometer data, is only representative of the footprint area of the scintillometer, whose size depends strongly on the synoptic conditions.
AB - We conduct a high-resolution large-eddy simulation (LES) case study in order to investigate the effects of surface heterogeneity on the (local) structure parameters of potential temperature CT 2 and specific humidity Cq 2 in the convective boundary layer (CBL). The kilometre-scale heterogeneous land-use distribution as observed during the LITFASS-2003 experiment was prescribed at the surface of the LES model in order to simulate a realistic CBL development from the early morning until early afternoon. The surface patches are irregularly distributed and represent different land-use types that exhibit different roughness conditions as well as near-surface fluxes of sensible and latent heat. In the analysis, particular attention is given to the Monin–Obukhov similarity theory (MOST) relationships and local free convection (LFC) scaling for structure parameters in the surface layer, relating CT 2 and Cq 2 to the surface fluxes of sensible and latent heat, respectively. Moreover we study possible effects of surface heterogeneity on scintillometer measurements that are usually performed in the surface layer. The LES data show that the local structure parameters reflect the surface heterogeneity pattern up to heights of 100–200 m. The assumption of a blending height, i.e. the height above the surface where the surface heterogeneity pattern is no longer visible in the structure parameters, is studied by means of a two-dimensional correlation analysis. We show that no such blending height is found at typical heights of scintillometer measurements for the studied case. Moreover, Cq 2 does not follow MOST, which is ascribed to the entrainment of dry air at the top of the boundary layer. The application of MOST and LFC scaling to elevated CT 2 data still gives reliable estimates of the surface sensible heat flux. We show, however, that this flux, derived from scintillometer data, is only representative of the footprint area of the scintillometer, whose size depends strongly on the synoptic conditions.
KW - Convective boundary layer
KW - Large-eddy simulation
KW - Scintillometry
KW - Surface heterogeneity
KW - Turbulent structure parameter
UR - http://www.scopus.com/inward/record.url?scp=85027951125&partnerID=8YFLogxK
U2 - 10.1007/s10546-014-9955-x
DO - 10.1007/s10546-014-9955-x
M3 - Article
AN - SCOPUS:85027951125
VL - 153
SP - 441
EP - 470
JO - Boundary-Layer Meteorology
JF - Boundary-Layer Meteorology
SN - 0006-8314
IS - 3
ER -