Potential temperature, specific humidity and wind profiles measured by radiosondes under unstable but windy conditions during FIFE in northeastern Kansas were analyzed within the framework of Monin-Obukhov similarity. Around 86% of these profiles were found to have a height range over which the similarity, formulated in terms of the Businger-Dyer functions, is valid and for which the resulting surface fluxes are in good agreement with independent measurements at ground stations. When scaled with the surface roughness z0= 1.05 m and the displacement height d0= 26.9 m, for the potential temperature this height range was 45 (±31) ≤ (z - d0)/z0≤ 104 (±54) and the comparison of the profile-derived surface fluxes with the independent measurements gave a correlation coefficient of r = 0.96. For the specific humidity these values are 42 (±29) ≤ (z - d0)/z0≤ 96 (±38) and r = 0.94. In terms of the height of the bottom of the inversion Hi, in the morning hours the upper limit of (z - d0) in the Monin-Obukhov layer is approximately 0.3 Hi, whereas for a fully developed ABL it is closer to 0.1 Hi. Probably, as a result of the short sampling times and perhaps also of the small gradients under the windy conditions, the exact height range of validity was difficult to establish from a mere inspection of these profiles. © 1990 Kluwer Academic Publishers.
