Submitted to: Agricultural and Forest Meteorology Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: November 6, 1998
Publication Date: N/A
Technical Abstract: The aerodynamic properties of roughness length and displacement height of corn and soybean canopies play an important role in the transfer processes of heat and water vapor between the canopy and atmosphere. These two parameters can be estimated from profile measurements of wind speed and temperature above a canopy during neutral conditions. This approach often results in few data points over the course of a growing season which can lead to errors in understanding the seasonal dynamics of heat and water vapor transfer from corn and soybean canopies. A study was conducted in the Walnut Creek Watershed near Ames, IA to evaluate two aerodynamic properties, roughness length of the canopy surface and displacement height of the mean wind flow above a corn and soybean canopy for an entire season. Wind speed and temperature profiles were measured above the surface throughout the course of a growing season for two very different crops, both which began as bare soil and ended with 3 and 1 m tall corn and soybean canopies respectively. The chi squared minimization technique was performed on the data which allowed for evaluating roughness lengths and displacement heights under a wide range of conditions. Results showed that the chi squared method provides an approach for rigorously evaluating canopy aerodynamic parameters allowing for more data to be included in the process. Estimates for roughness lengths and displacement heights were consistent with those reported in the literature.