Laboratory and Numerical Studies of the Convective Boundary Layer Capped by a Strong Inversion

Abstract The inversion layer (IL) of a clear-sky, buoyancy-driven convective boundary layer is investigated using large-eddy simulations covering a wide range of convective Richardson numbers. A new model of the IL is suggested and tested. The model performs better than previous first-order models of the entrainment and provides physical insights into the main controls of the mixed-layer and IL growths. A consistent prognostic equation of the IL growth is derived, with explicit dependence on the position of the minimum buoyancy flux, convective Richardson number, and relative stratification across the inversion G. The IL model expresses the interrelationship between the position and magnitude of the minimum buoyancy flux and inversion-layer depth. These relationships emphasize why zero-order jump models of the convective boundary layer perform well under a strong inversion and show that these models miss the additional parameter G to fully characterize the entrainment process under a weak inversion. Additionally, the position of the minimum buoyancy flux within the new IL model is shown to be a key component of convective boundary layer entrainment. The new IL model is sufficiently simple to be used in numerical weather prediction or general circulation models as a way to resolve the IL in a low-vertical-resolution model.

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Wind tunnel study of convective boundary layer capped by a strong inversion layer

Wind Engineers JAWE ◽

10.5359/jawe.1998.75_25 ◽

1998 ◽

Vol 1998 (75) ◽

pp. 25-30 ◽

Cited By ~ 2

Author(s):

Yuji OHYA ◽

Kenichi HAYASHI ◽

Suguru MITSUE ◽

Kenji MANAGI

Keyword(s):

Boundary Layer ◽

Wind Tunnel ◽

Convective Boundary Layer ◽

Inversion Layer ◽

Convective Boundary ◽

Strong Inversion ◽

Wind Tunnel Study

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Observational and Numerical Evidence of Depressed Convective Boundary Layer Heights near a Mountain Base

Journal of Applied Meteorology and Climatology ◽

10.1175/2007jamc1651.1 ◽

2008 ◽

Vol 47 (4) ◽

pp. 1017-1026 ◽

Cited By ~ 22

Author(s):

Stephan F. J. De Wekker

Keyword(s):

Boundary Layer ◽

Convective Boundary Layer ◽

Layer Growth ◽

Air Pollutant ◽

Convective Boundary ◽

Layer Height ◽

Boundary Layer Height ◽

Numerical Studies ◽

Thermally Driven ◽

Show Evidence

Abstract Recent field and numerical studies show evidence of the existence of a convective boundary layer height depression near a mountain base. This depression can have implications for air pollutant transport and concentrations in complex terrain. To investigate the mechanisms underlying this phenomenon, idealized simulations with a mesoscale numerical model are performed and combined with available observations. The idealized simulations with a single mountain ridge of various dimensions suggest that the depression evolves in time, is most pronounced in the late afternoon, and becomes larger as slope steepness increases. Observations and modeling results show that the atmosphere is heated more intensely near the mountain base than far away from the mountain base, not only inside the boundary layer but also above. The enhanced heating aloft affects boundary layer growth near the mountain base and is associated with the boundary layer height depression. An analysis of the different terms in the temperature tendency equation indicates that vertical and horizontal advection of warm air, associated with the thermally driven circulation along the mountain slope, play a role in this enhanced heating aloft.

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