Jm. Jacobs et W. Brutsaert, Momentum roughness and view-angle dependent heat roughness at a Southern Great Plains test-site, J HYDROL, 211(1-4), 1998, pp. 61-68
Surface roughness parameters were determined for harvested wheat fields ove
r level terrain at the US Department of Energy's Cloud and Radiation Testbe
d (CART) site in north-central Oklahoma. Measurements of wind speed and tem
perature were made by radiosondes and instruments mounted on 2 and 10 m tow
ers during neutral and unstable atmospheric conditions in the atmospheric s
urface layer. Surface temperatures were measured radiatively over 750 m tra
jectories. Roughness heights were calculated for the region using the Monin
-Obukhov similarity theory. The scalar roughness and the local momentum rou
ghness were determined using wind speed measurements at 10 m and temperatur
e measurements at 2 m combined with eddy correlation measurements for u(*).
The scalar roughness z(oh) was determined to be 0.0021 and 0.0038 m for th
e nadir and the off-nadir viewing angle, respectively. It was estimated tha
t the displacement height d is negligible. A regional momentum surface roug
hness of z(o) = 0.15 m was determined by means of the radiosonde profiles.
Good agreement (r = 0.92) between measured and calculated sensible heat flu
x values was found using an independent data set of radiosonde profiles. (C
) 1998 Elsevier Science B.V. All rights reserved.