Development and test of a multifactorial parameterization scheme of land surface aerodynamic roughness length for flat land surfaces with short vegetation

The Weather Research and Forecasting (WRF) modeling system obtains the aerodynamic roughness length (z0) from a land use (LU) lookup table. The effective aerodynamic roughness length (z0eff) was estimated for the island of Taiwan by considering the individual roughness lengths (z0i) of the underlying LU types within a modeling grid box. Two z0eff datasets were prepared: one using the z0i from the default LU lookup table and the other using the observed z0i for three LU types (urban, dry cropland and pasture, and irrigated cropland and pasture). The spatial variability of the z0eff distribution was higher than that of the LU table-based z0 distribution. Three WRF sensitivity experiments were performed: (1) dominant LU table-based z0 (namely, S1), (2) z0eff estimated from the default z0i (namely, S2), and (3) z0eff estimated from the observed z0i (namely, S3). Comparisons of the thermal field, temperature, and surface sensible and latent heat fluxes revealed no significant differences among the three simulations. The wind field overestimation and surface momentum flux underestimation in S1 were reduced in S2 and S3, and these improvements were more prominent over areas with highly heterogeneous land surface conditions.

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

Hydrology and Earth System Sciences ◽

10.5194/hess-14-2661-2010 ◽

2010 ◽

Vol 14 (12) ◽

pp. 2661-2669 ◽

Cited By ~ 21

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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The influences of thermodynamic characteristics on aerodynamic roughness length over land surface

Acta Meteorologica Sinica ◽

10.1007/s13351-013-0209-5 ◽

2013 ◽

Vol 27 (2) ◽

pp. 249-262 ◽

Cited By ~ 2

Author(s):

Qiang Zhang ◽

Tong Yao ◽

Ping Yue ◽

Liyang Zhangf ◽

Jian Zeng

Keyword(s):

Land Surface ◽

Roughness Length ◽

Thermodynamic Characteristics ◽

Aerodynamic Roughness Length ◽

Aerodynamic Roughness

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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

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-5-2933-2012 ◽

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.

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