Rd. Crago et W. Brutsaert, THE ESTIMATION OF SURFACE MOMENTUM FLUX UNDER UNSTABLE CONDITIONS FROM THE ATMOSPHERIC-PRESSURE FIELD, Water resources research, 30(3), 1994, pp. 617-623
Data from FIFE (the First International Satellite Land Surface Climato
logy Project (ISLSCP) Field Experiment) were used in an atmospheric bo
undary layer bulk similarity formulation to derive values of the frict
ion velocity, u (i.e., the shear stress), from surface geostrophic wi
nd measurements under unstable conditions. Several stability-dependent
forms for the similarity functions B (corresponding to the x directio
n geostrophic wind, u(g)) and B(w) (corresponding to the scalar geostr
ophic wind speed, G) were tested. Formulations to calculate u from G
were more successful than those which used only u(g). However, the dep
endency of B, B(w), or the geostrophic drag coefficient, C(G) = mu/G,
on either stability or baroclinicity was observed to be relatively we
ak. For FIFE, a constant value of B(w) = 1.99 agreed with the referenc
e u values almost as well as the best stability-dependent formulation
s. A constant value Of C(G) = 0.0883, used with measured values of G,
gave an unbiased estimate of u, on average, with a correlation r = 0.
80.