scholarly journals A complementary evaporation approach to the scalar roughness length

2005 ◽  
Vol 41 (6) ◽  
Author(s):  
Richard Crago ◽  
Nicole Hervol ◽  
Raphael Crowley
Keyword(s):  
Roughness Length ◽  
Scalar Roughness Length

scholarly journals On the effective aerodynamic and scalar roughness length of Weddell Sea ice

2011 ◽  
Vol 116 (D19) ◽  
Author(s):  
Alexandra I. Weiss ◽  
John King ◽  
Tom Lachlan-Cope ◽  
Russ Ladkin
Keyword(s):  
Sea Ice ◽  
Roughness Length ◽  
Weddell Sea ◽  
Scalar Roughness Length

Reconciling the Reynolds number dependence of scalar roughness length and laminar resistance

2017 ◽  
Vol 44 (7) ◽  
pp. 3193-3200 ◽  
Author(s):  
Dan Li ◽  
Angela Rigden ◽  
Guido Salvucci ◽  
Heping Liu
Keyword(s):  
Reynolds Number ◽  
Roughness Length ◽  
Scalar Roughness Length ◽  
Reynolds Number Dependence

Critical Evaluation of Scalar Roughness Length Parametrizations Over a Melting Valley Glacier

2011 ◽  
Vol 139 (2) ◽  
pp. 307-332 ◽  
Author(s):  
Xiaofeng Guo ◽  
Kun Yang ◽  
Long Zhao ◽  
Wei Yang ◽  
Shenghai Li ◽  
...  
Keyword(s):  
Roughness Length ◽  
Critical Evaluation ◽  
Valley Glacier ◽  
Scalar Roughness Length

scholarly journals Roughness Lengths for Momentum and Heat Derived from Outdoor Urban Scale Models

2007 ◽  
Vol 46 (7) ◽  
pp. 1067-1079 ◽  
Author(s):  
M. Kanda ◽  
M. Kanega ◽  
T. Kawai ◽  
R. Moriwaki ◽  
H. Sugawara
Keyword(s):  
Wind Direction ◽  
Roughness Length ◽  
Scale Dependence ◽  
Scale Model ◽  
Small Scale ◽  
Physical Scale ◽  
Scale Models ◽  
Roughness Lengths ◽  
Urban Sites ◽  
Obstacle Height

Abstract Urban climate experimental results from the Comprehensive Outdoor Scale Model (COSMO) were used to estimate roughness lengths for momentum and heat. Two different physical scale models were used to investigate the scale dependence of the roughness lengths; the large scale model included an aligned array of 1.5-m concrete cubes, and the small scale model had a geometrically similar array of 0.15-m concrete cubes. Only turbulent data from the unstable boundary layers were considered. The roughness length for momentum relative to the obstacle height was dependent on wind direction, but the scale dependence was not evident. Estimated values agreed well with a conventional morphometric relationship. The logarithm of the roughness length for heat relative to the obstacle height depended on the scale but was insensitive to wind direction. COSMO data were used successfully to regress a theoretical relationship between κB−1, the logarithmic ratio of roughness length for momentum to heat, and Re*, the roughness Reynolds number. Values of κB−1 associated with Re* for three different urban sites from previous field experiments were intercompared. A surprising finding was that, even though surface geometry differed from site to site, the regressed function agreed with data from the three urban sites as well as with the COSMO data. Field data showed that κB−1 values decreased as the areal fraction of vegetation increased. The observed dependency of the bulk transfer coefficient on atmospheric stability in the COSMO data could be reproduced using the regressed function of Re* and κB−1, together with a Monin–Obukhov similarity framework.

scholarly journals Comparison of satellite microwave backscattering (ASCAT) and visible/near-infrared reflectances (PARASOL) for the estimation of aeolian aerodynamic roughness length in arid and semi-arid regions

2012 ◽  
Vol 5 (2) ◽  
pp. 2933-2957
Author(s):  
C. Prigent ◽  
C. Jiménez ◽  
J. Catherinot
Keyword(s):  
Arid Regions ◽  
Near Infrared ◽  
Roughness Length ◽  
Aerodynamic Roughness Length ◽  
Sources Of Information ◽  
Transport Models ◽  
Dust Transport ◽  
Infrared Observations ◽  
Aerodynamic Roughness ◽  
Semi Arid

Abstract. Previous studies examined the possibility to estimate the aeolian aerodynamic roughness length from satellites, either from visible/near-infrared observations or from microwave backscattering measurements. Here we compare the potential of the two approaches and propose to merge the two sources of information to benefit from their complementary aspects, i.e. the high spatial resolution of the visible/near-infrared (PARASOL part of the A-Train) and the independence from atmospheric contamination of the active microwaves (ASCAT on board MetOp). A global map of the aeolian aerodynamic roughness length at 6 km resolution is derived, for arid and semi-arid regions. It shows very good consistency with the existing information on the properties of these surfaces. The dataset is available to the community, for use in atmospheric dust transport models.

The Percolation of Liquid Through a Compliant Seal—An Experimental and Theoretical Study

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Sorin-Cristian Vlădescu ◽  
Carmine Putignano ◽  
Nigel Marx ◽  
Tomas Keppens ◽  
Tom Reddyhoff ◽  
...  
Keyword(s):  
Surface Energy ◽  
Capillary Pressure ◽  
Contact Pressure ◽  
Roughness Length ◽  
Theoretical Study ◽  
Theoretical Explanation ◽  
Channel Section ◽  
Hydrophilic Surfaces ◽  
New Apparatus ◽  
The Impact

New apparatus is described to simulate a compliant seal interface, allowing the percolation of liquid to be viewed by a fluorescence microscope. A model, based on the boundary element (BE) methodology, is used to provide a theoretical explanation of the observed behavior. The impact of contact pressure, roughness, and surface energy on percolation rates are characterized. For hydrophilic surfaces, percolation will always occur provided a sufficient number of roughness length scales are considered. However, for hydrophobic surfaces, the inlet pressure must overcome the capillary pressure exerted at the minimum channel section before flow can occur.

scholarly journals Aerodynamic roughness length estimation from very high-resolution imaging LIDAR observations over the Heihe basin in China

2010 ◽  
Vol 14 (12) ◽  
pp. 2661-2669 ◽  
Author(s):  
J. Colin ◽  
R. Faivre
Keyword(s):  
Remote Sensing ◽  
Surface Roughness ◽  
Land Cover ◽  
River Basin ◽  
Land Surface ◽  
Surface Density ◽  
Roughness Length ◽  
Aerodynamic Roughness Length ◽  
Passive Remote Sensing ◽  
Aerodynamic Roughness

Abstract. Roughness length of land surfaces is an essential variable for the parameterisation of momentum and heat exchanges. The growing interest in the estimation of the surface turbulent flux parameterisation from passive remote sensing leads to an increasing development of models, and the common use of simple semi-empirical formulations to estimate surface roughness. Over complex surface land cover, these approaches would benefit from the combined use of passive remote sensing and land surface structure measurements from Light Detection And Ranging (LIDAR) techniques. Following early studies based on LIDAR profile data, this paper explores the use of imaging LIDAR measurements for the estimation of the aerodynamic roughness length over a heterogeneous landscape of the Heihe river basin, a typical inland river basin in the northwest of China. The point cloud obtained from multiple flight passes over an irrigated farmland area were used to separate the land surface topography and the vegetation canopy into a Digital Elevation Model (DEM) and a Digital Surface Model (DSM) respectively. These two models were then incorporated in two approaches: (i) a strictly geometrical approach based on the calculation of the plan surface density and the frontal surface density to derive a geometrical surface roughness; (ii) a more aerodynamic approach where both the DEM and DSM are introduced in a Computational Fluid Dynamics model (CFD). The inversion of the resulting 3-D wind field leads to a fine representation of the aerodynamic surface roughness. Examples of the use of these three approaches are presented for various wind directions together with a cross-comparison of results on heterogeneous land cover and complex roughness element structures.

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