Translating wind measurements from weather stations to agricultural crops

Allen, Richard G. and Wright, James L. (1997) Translating wind measurements from weather stations to agricultural crops. Journal of Hydrologic Engineering. 2(1):26-35.

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Abstract

Wind-speed profiles within the internal boundary layer
(IBL) are determined by the roughness of the underlying surface
and the general velocity of the air mass. Most evapotranspiration
(ET) estimation equations, especially the Penman or
Penman-Monteith types, employ this principle by measuring
weather data at an elevation z above the ground surface. Aerodynamic
resistance algorithms used in the Penman-Monteith
equation assume that wind speeds measured at height z are
characteristic of the crop being evaluated and can be extrapolated
to the vegetation surface using logarithmic profiles
characteristic of the crop roughness and height. In many studies,
however, meteorological data are from standard types of
weather stations situated over clipped grass or bare soil, rather
than the surface in question. Differences in aerodynamic
roughness affect measured wind velocities and the subsequent
predictions of aerodynamic resistance (ra). Magnitudes of ra,
and bulk surface (stomatal) resistance for agricultural crops
are often similar, averaging about 40-60 s/m-1 when wind
speeds 2 m above the crops range from 2 to 3 m/s-1. Although
surface resistance is generally known with less certainty than
ra, it still may be important to translate wind-speed data to
better predict ra, and ET using the Penman-Monteith equation
for a specific crop.

Item Type:	Article
NWISRL Publication Number:	0934
Subjects:	Research methodology Mass Import - autoclassified (may be erroneous)
Depositing User:	Dan Stieneke
Date Deposited:	20 Nov 2010 21:54
Last Modified:	22 Nov 2016 20:10
Item ID:	676
URI:	https://eprints.nwisrl.ars.usda.gov/id/eprint/676