An Evaluation of the Scale at which Ground-Surface Heat Flux Patchiness Affects the Convective Boundary Layer Using Large-Eddy Simulations

Abstract The effects on the convective boundary layer (CBL) of surface heterogeneities produced by surface sensible heat flux waves with different means, amplitudes, and wavelengths were investigated here. The major objective of this study was to evaluate at which scale surface heterogeneity starts to significantly affect the heat fluxes in the CBL. The large-eddy simulation option of the Regional Atmospheric Modeling System developed at Colorado State University was used for that purpose. Avissar et al. evaluated this model against observations and demonstrated its reliability. It appears that the impact of amplitude and wavelength of a heat wave is nonlinearly dependent upon the mean heating rate. The circulations (or rolls) resulting from surface heterogeneity are strong when the amplitude and the wavelength of the heat wave are large, especially at low mean heating rate. In that case the profiles of horizontally averaged variables are quite strongly modified in the CBL. The potential temperature is no...

[1]  Roger A. Pielke,et al.  Landscape-Induced Atmospheric Flow and its Parameterization in Large-Scale Numerical Models , 1995 .

[2]  R. Pielke,et al.  Nonlinear Influence of Mesoscale Land Use on Weather and Climate , 1991 .

[3]  Roger A. Pielke,et al.  Large-eddy simulations of the effects of hilly terrain on the convective boundary layer , 1992 .

[4]  T. Clark.  A small-scale dynamic model using a terrain-following coordinate transformation , 1977 .

[5]  Ulrich Schumann,et al.  Coherent structure of the convective boundary layer derived from large-eddy simulations , 1989, Journal of Fluid Mechanics.

[6]  Roger A. Pielke,et al.  A parameterization of heterogeneous land surfaces for atmospheric numerical models and its impact on regional meteorology , 1989 .

[7]  R. Arritt,et al.  Nonclassical mesoscale circulations caused by surface sensible heat-flux gradients , 1992 .

[8]  W. Cotton,et al.  Large-eddy simulations of thermally forced circulations in the convective boundary layer. Part I: A small-scale circulation with zero wind , 1991 .

[9]  R. Pielke,et al.  Evaluation of Soil Moisture Effects on the Generation and Modification of Mesoscale Circulations , 1984 .

[10]  Chin-Hoh Moeng,et al.  The Effects of Nonhomogeneous Surface Fluxes on the Convective Boundary Layer: A Case Study Using Large-Eddy Simulation. , 1990 .

[11]  U. Schumann,et al.  Direct numerical simulation of thermal convection over a wavy surface , 1989 .

[12]  Monique Y. Leclerc,et al.  How large must surface inhomogeneities be before they influence the convective boundary layer structure? A case study , 1995 .

[13]  Fei Chen,et al.  Impact of Land-Surface Moisture Variability on Local Shallow Convective Cumulus and Precipitation in Large-Scale Models , 1994 .

[14]  J. Andre,et al.  Regional estimates of heat and evaporation fluxes over non-homogeneous terrain. Examples from the HAPEX-MOBILHY programme , 1990 .

[15]  Roni Avissar,et al.  Sensitivity of shallow convective precipitation induced by land surface heterogeneities to dynamical and cloud microphysical parameters , 1996 .

[16]  E. Eloranta,et al.  An Evaluation of the Large-Eddy Simulation Option of the Regional Atmospheric Modeling System in Simulating a Convective Boundary Layer: A FIFE Case Study , 1998 .

[17]  John C. Wyngaard,et al.  Statistics of Conservative Scalars in the Convective Boundary Layer , 1984 .

[18]  E. F. Bradley,et al.  Flux-Profile Relationships in the Atmospheric Surface Layer , 1971 .

[19]  George S. Young,et al.  Turbulence Structure of the Convective Boundary Layer. Part II. Phonenix 78 Aircraft Observations of Thermals and Their Environment , 1988 .

[20]  W. Cotton,et al.  Large-eddy simulations of thermally forced circulations in the convective boundary layer. Part II: The effect of changes in wavelength and wind speed , 1992 .

[21]  R. Stull.  An Introduction to Boundary Layer Meteorology , 1988 .

[22]  R. Pielke,et al.  A comprehensive meteorological modeling system—RAMS , 1992 .

[23]  J. Deardorff.  Three-dimensional numerical study of the height and mean structure of a heated planetary boundary layer , 1974 .

[24]  Roni Avissar,et al.  Using Similarity Theory to Parameterize Mesoscale Heat Fluxes Generated by Subgrid-Scale Landscape Discontinuities in GCMs , 1995 .

[25]  R. Pielke,et al.  Evaluation of vegetation effects on the generation and modification of mesoscale circulations , 1988 .

[26]  C. Moeng.  A Large-Eddy-Simulation Model for the Study of Planetary Boundary-Layer Turbulence , 1984 .

[27]  Richard C. J. Somerville,et al.  On the use of a coordinate transformation for the solution of the Navier-Stokes equations , 1975 .

[28]  R. Pielke,et al.  Linear Impact of Thermal Inhomogeneities on Mesoscale Atmospheric Flow with Zero Synoptic Wind , 1991 .