Momentum roughness and view-angle dependent heat roughness at a Southern Great Plains test-site
Abstract
Surface roughness parameters were determined for harvested wheat fields over level terrain at the US Department of Energy's Cloud and Radiation Testbed (CART) site in north-central Oklahoma. Measurements of wind speed and temperature were made by radiosondes and instruments mounted on 2 and 10 m towers during neutral and unstable atmospheric conditions in the atmospheric surface layer. Surface temperatures were measured radiatively over 750 m trajectories. Roughness heights were calculated for the region using the Monin–Obukhov similarity theory. The scalar roughness and the local momentum roughness were determined using wind speed measurements at 10 m and temperature measurements at 2 m combined with eddy correlation measurements for . The scalar roughness zoh was determined to be 0.0021 and 0.0038 m for the nadir and the off-nadir viewing angle, respectively. It was estimated that the displacement height d is negligible. A regional momentum surface roughness of zo=0.15 m was determined by means of the radiosonde profiles. Good agreement (r=0.92) between measured and calculated sensible heat flux values was found using an independent data set of radiosonde profiles.
Department
Earth Systems Research Center
Publication Date
11-1-1998
Journal Title
Journal of Hydrology
Publisher
Elsevier
Digital Object Identifier (DOI)
Document Type
Article
Recommended Citation
Jacobs, J.M. and W. Brutsaert. 1998. Momentum roughness and view-angle dependent heat roughness at a Southern Great Plains test-site, Journal of Hydrology, 211, 61-68.
Rights
© 1998 Elsevier Science B.V. All rights reserved.