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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Research » Publications at this Location » Publication #40351
Title: WINDBREAK SHELTER EFFECTS ON SURFACE ENERGY BALANCE COMPONENTS

Author
item Prueger, John
item Sauer, Thomas
item TAKLE EUGENE S - IOWA STATE UNIVERSITY
item LITVINA IRINA V - AGROPHYSICAL RES. INST.
item SCHMIDT R A - USDA-FOREST SERVICE
item BRANDLE JAMES R - UNIVERSITY OF NEBRASKA
item Hatfield, Jerry

Submitted to: Meteorological Observations and Instrumentation Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/31/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Wind barriers produce significant and complex changes in local microclimate. Previous investigations on the effect of windbreak shelter on agronomic crops have often evaluated crop yield and/or water use with distance from the shelter. The specific mechanisms responsible for the observed microclimate modification remain uncertain and hinder progress in shelterbelt design. The objective of this study was to use modern micrometeorological techniques to measure all surface energy balance components upwind and in the lee of wooded shelterbelts, to determine the effect of shelter on the partitioning of available energy at the plant surface. Measurements were taken at the University of Nebraska-Lincoln Field Laboratory, near Mead, Nebraska, over a 5-day period in July 1994. The shelterbelts were composed of two rows of 12-m-tall trees while the surfaces studied included wheat stubble, alfalfa, and alfalfa stubble. Sensible and latent heat fluxes were measured using eddy correlation techniques, while net radiometers and soil heat flow transducers were used to measure net radiation and conductive soil heat flux. More available energy was partitioned into latent than sensible heat flux for both the wheat and alfalfa stubble surfaces; however, the reverse was true for the alfalfa canopy, where nearly all the available energy was partitioned to sensible heat flux. Also, the leeward location had greater latent and sensible heat flux and lower conductive soil heat flux as compared to the upwind location for all surfaces except the alfalfa canopy. There was little difference in net radiation between the upwind and leeward positions. The higher latent and sensible heat fluxes behind shelter are likely due to turbulence created by the shelterbelt.