Comments on “Toward Evaluation of Heat Fluxes in the Convective Boundary Layer”

1996 ◽  
Vol 35 (8) ◽  
pp. 1370-1373 ◽  
Author(s):  
Mark F. Hibberd
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Heat Fluxes ◽  
Convective Boundary

scholarly journals Reexamining the Gradient and Countergradient Representation of the Local and Nonlocal Heat Fluxes in the Convective Boundary Layer

2018 ◽  
Vol 75 (7) ◽  
pp. 2317-2336 ◽  
Author(s):  
Bowen Zhou ◽  
Shiwei Sun ◽  
Kai Yao ◽  
Kefeng Zhu
Keyword(s):  
Boundary Layer ◽  
Temperature Gradient ◽  
Mixed Layer ◽  
Convective Boundary Layer ◽  
Correction Term ◽  
Potential Temperature ◽  
Heat Fluxes ◽  
Gradient Term ◽  
Convective Boundary ◽  
Upper Mixed Layer

Abstract Turbulent mixing in the daytime convective boundary layer (CBL) is carried out by organized nonlocal updrafts and smaller local eddies. In the upper mixed layer of the CBL, heat fluxes associated with nonlocal updrafts are directed up the local potential temperature gradient. To reproduce such countergradient behavior in parameterizations, a class of planetary boundary layer schemes adopts a countergradient correction term in addition to the classic downgradient eddy-diffusion term. Such schemes are popular because of their simple formulation and effective performance. This study reexamines those schemes to investigate the physical representations of the gradient and countergradient (GCG) terms, and to rebut the often-implied association of the GCG terms with heat fluxes due to local and nonlocal (LNL) eddies. To do so, large-eddy simulations (LESs) of six idealized CBL cases are performed. The GCG fluxes are computed a priori with horizontally averaged LES data, while the LNL fluxes are diagnosed through conditional sampling and Fourier decomposition of the LES flow field. It is found that in the upper mixed layer, the gradient term predicts downward fluxes in the presence of positive mean potential temperature gradient but is compensated by the upward countergradient correction flux, which is larger than the total heat flux. However, neither downward local fluxes nor larger-than-total nonlocal fluxes are diagnosed from LES. The difference reflects reduced turbulence efficiency for GCG fluxes and, in terms of physics, conceptual deficiencies in the GCG representation of CBL heat fluxes.

scholarly journals ESTIMATIVA DA PARTIÇÃO DE ENERGIA NA SUPERFÍCIE

2016 ◽  
Vol 38 ◽  
pp. 412
Author(s):  
Daiane De Vargas Brondani ◽  
Otávio Costa Acevedo ◽  
Fabíola Valente
Keyword(s):  
Boundary Layer ◽  
Latent Heat ◽  
Convective Boundary Layer ◽  
Method Development ◽  
Surface Fluxes ◽  
Heat Fluxes ◽  
Specific Humidity ◽  
Ratio Method ◽  
Convective Boundary ◽  
Monthly Scale

This paper is a complementary analysis to method development, which proposes to estimate the energy partition on the surface by Bowen ratio method and height of convective boundary layer on the monthly scale based on the average temporal evolution of the variables air temperature and specific humidity. The basic hypothesis is that the evolution of these quantities is controlled solely by the convergence of surface fluxes of sensible and latent heat. This assumption is valid for monthly scale and in regions of middle latitudes away from the coast. Thus, it is assumed that the advective terms of the balance equation of these quantities in the convective boundary layer, the prefrontal situations and post-frontal have opposite sign. Therefore, using for a longer time scale than the typical scale of the passage of synoptic systems, the cancellation terms of hypothesis can be tested. In this study, the method is applied to the region of Santa Maria, where it is assumed that the conditions allowing despise the advective terms in monthly scale are valid. When testing the method on different time scales: 5,10,15,20 and 30 days, smaller errors temperature and specific humidity were for 15 and 30 days, while the sensible heat and latent heat fluxes showed lower relative errors at 20 and 30 days, respectively.

scholarly journals Parameterization of Inversion Breakup in Idealized Valleys. Part I: The Adjustable Model Parameters

2006 ◽  
Vol 45 (4) ◽  
pp. 600-608 ◽  
Author(s):  
N. M. Zoumakis ◽  
G. A. Efstathiou
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Convective Boundary Layer ◽  
Sensible Heat Flux ◽  
Layer Growth ◽  
Heat Fluxes ◽  
Future Research ◽  
Model Parameters ◽  
Sensible Heat ◽  
Convective Boundary

Abstract The factors that affect the atmospheric energy budget approach used in the thermodynamic valley inversion destruction model of Whiteman and McKee are investigated theoretically. The height at which the sinking inversion top meets the rising convective boundary layer to destroy valley inversions can be uniquely determined by the topographic characteristics of the valley and an adjustable model parameter, relating to the fraction of sensible heat flux going to convective boundary layer growth, through a simple parabolic relationship. The time required to break a temperature inversion can be expressed with very good approximation as a simple power-law function of the topographic parameters and the fraction of extraterrestrial solar flux that is partitioned to sensible heat flux in the valley atmosphere. The theoretical estimates compare very favorably to predictions from the bulk thermodynamic model of Whiteman and McKee. A new approach to handle time-dependent sensible heat fluxes is outlined. The paper ends with recommendations for future research.

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