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United States Department of Agriculture

Agricultural Research Service

Title: Spatial and Temporal Variation in Evapotranspiration Using Raman Lidar

Authors
item Eichinger, William - UNIV. OF IA
item Cooper, Daniel - LOS ALAMOS NATIONAL LAB
item Hipps, Lawrence - UTAH STATE UNIVERSITY
item Kustas, William
item Neale, Christopher - UTAH STATE UNIVERSITY
item Prueger, John

Submitted to: Advances in Water Resources
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 5, 2006
Publication Date: June 5, 2006
Citation: Eichinger, W.E., Cooper, D.I., Hipps, L.E., Kustas, W.P., Neale, C.M., Prueger, J.H. 2006. Spatial and temporal variation in evapotranspiration using Raman Lidar. Advances in Water Resources. 29:369–381.

Interpretive Summary: A Light Detection And Ranging (LIDAR) instrument from Los Alamos National Laboratory has been used to make high resolution (25 m grid size) estimates of the evapotranspiration rate over adjacent corn and soybean canopies. The data used was taken during the Soil Moisture-Atmosphere Coupling Experiment (SMACEX) conducted in the Walnut Creek Watershed near Ames, Iowa in June and July, 2002. The LIDAR makes three-dimensional measurements of the water vapor content of the atmosphere directly above the canopy that are inverted using flux-gradient theory. This may be used to examine the relationship between evapotranspiration and surface moisture/soil type variability across a landscape. LIDAR estimates of evapotranspiration reveal a high degree of spatial variability over corn and soybean fields that may be associated with small elevation changes in the area. The spatial patterns in evapotranspiration are not related to a power law relationship for soil moisture found by other investigators. Therefore, other factors, such as terrain and soil type and crop cover variability must be considered.

Technical Abstract: The Los Alamos Raman lidar has been used to make high resolution (25m) estimates of the evapotranspiration rate over adjacent corn and soybean canopies. The lidar makes three-dimensional measurements of the water vapor content of the atmosphere directly above the canopy that are inverted using Monin-Obukhov similarity theory. This may be used to examine the relationship between evapotranspiration and surface moisture/soil type. Lidar estimates of evapotranspiration reveal a high degree of spatial variability over corn and soybean fields that may be associated with small elevation changes in the area. The spatial structure of the variability is characterized using a structure function approach. The power law relationship found by other investigators for soil moisture is not clear in the data. The data used was taken during the Soil Moisture-Atmosphere Coupling Experiment (SMACEX) conducted in the Walnut Creek Watershed near Ames, Iowa in June and July, 2002.

Last Modified: 9/2/2014
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