scholarly journals UM ESTUDO DO EFEITO DE OBSTRUÇÕES NO ESCOAMENTO DE SUBMESO NA CAMADA LIMITE CONVECTIVA

2016 ◽  
Vol 38 ◽  
pp. 252
Author(s):  
Viviane Da Silva Guerra ◽  
Otávio Costa Acevedo ◽  
Luiz Eduardo Medeiros ◽  
Adriano Battisti ◽  
Thaís Freitas Dill
Keyword(s):  
Boundary Layer ◽  
Urban Areas ◽  
Ground Cover ◽  
Transmission Factor ◽  
Local Surface ◽  
Experimental Site ◽  
Convective Boundary ◽  
Large Variability ◽  
Pampa Region ◽  
Experimental Level

The equations built over the years in the study of planetary boundary layer, although often based on experimental level, were created to idealized situations like, homogeneous surfaces flat, free from obstacles and steady state conditions. However such homogeneity situation is far from reality, because the earth’s surface features a large variability in topography, ground cover and urban areas. This paper presents a proposal to show the influence of the variability of the local surface as the obstacle effect on the flow in the timescale still small known, the Submeso in Convective Boundary Layer. To prove this effect was found a Transmission Factor for each wind sector in the eight micrometeorological stations present in the experimental site of Pedras Altas in the Pampa region in the state of Rio Grande do Sul. Such Transmission Factor confirm the local influence of obstacles in filtering flow enabling identification of which quadrant the wind is more or less obstructed and even check in climbing time to osbtrução exerts greater impact.

scholarly journals The mixing height in urban areas: comparative study for Copenhagen

2004 ◽  
Vol 4 (3) ◽  
pp. 2839-2866 ◽  
Author(s):  
A. Baklanov ◽  
A. Kuchin
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Urban Areas ◽  
Central City ◽  
Estimation Methods ◽  
Mixing Height ◽  
Atmospheric Boundary Layers ◽  
Convective Boundary ◽  
Urban Rural ◽  
Marine Areas

Abstract. The urban boundary layer (UBL), in comparison with "rural" homogeneous atmospheric boundary layers, is characterised by greatly enhanced mixing, resulting from both the large surface roughness and increased surface heating, and by horizontal heterogeneity of the mixing height (MH) and other meteorological fields due to variations in surface roughness and heating from rural to central city areas. So, the UBL is considered as a specific case of the atmospheric boundary layer (ABL) over a non-homogeneous terrain. Therefore it is important to study how much the MH characteristics differ in urban and rural, marine or other more homogeneous areas. Most of the parameterisations of MH were developed for the conditions of a homogeneous terrain, so their applicability for urban conditions should be verified. Just a few authors suggested specific methods for MH determination in urban areas. In this paper the MH over urban, semi-urban, rural and marine areas of the Copenhagen metropolitan area is considered. Proceeding from the data from the Jægersborg radiosounding station measurement and analysis of different methods of the MH estimation, the peculiarities of the UBL and intercomparison of different MH estimation methods for urban and rural conditions are discussed. It is shown that the urban MH is considerably bigger for stably stratified (nocturnal) boundary layer cases in comparison with the "non-urban" MH. Daytime (usually the convective boundary layer) MH does not differ significatly in urban and "non-urban" sectors.

Estimation of turbulent heat fluxes and exchange coefficients for heat at Dumont d'Urville, East Antarctica

1999 ◽  
Vol 11 (1) ◽  
pp. 93-99 ◽  
Author(s):  
S. Argentini ◽  
G. Mastrantonio ◽  
A. Viola
Keyword(s):  
Boundary Layer ◽  
Heat Fluxes ◽  
East Antarctica ◽  
Turbulent Heat ◽  
Convective Boundary ◽  
Doppler Sodar ◽  
Turbulent Heat Fluxes ◽  
Unstable Boundary Layer ◽  
Sodar Measurements ◽  
The Antarctic

Simultaneous acoustic Doppler sodar and tethersonde measurements were used to study some of the characteristics of the unstable boundary layer at Dumont d'Urville, Adélie Land, East Antarctica during the summer 1993–94. A description of the convective boundary layer and its behaviour in connection with the wind regime is given along with the frequency distribution of free convection episodes. The surface heat flux has been evaluated using the vertical velocity variance derived from sodar measurements. The turbulent exchange coefficients, estimated by coupling sodar and tethered balloon measurements, are in strong agreement with those present in literature for the Antarctic regions.

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