Previous results of non-dimensional wind and temperature profiles as hmctions of c( = z/L) show systematic deviations between diierent experiments. These discrepancies are generally believed not to re8ect real differences but rather instrumental shortcomings. In particular, it is clear that flow distortion has not been adequately treated in most previous experiments. In the present paper, results are presented from a surface-layer field experiment where great care was taken to remove any effects from this kind of error and also to minimize other measuring errors. Data from about 90 30-min runs with turbulence measurements at three levels (3,6, and 14 m) and simultaneous profile data have been analysed to yield information on llux-gradient relationships for wind and temperature.The Bux measurements themselves show that the fluxes of momentum and sensible heat are constant within f 7 y0 on average for the entire 14 m layer in daytime conditions and when the stratification is slightly stable. For more stable conditions, the Bux starts to decrease systematically somewhere in the layer 6 to 14 m. From a large body of data for near-neutral conditions ( / cl 5 O.l), values are derived for von K&rmAn's constant: 0.40 f 0.01 and for &, at neutrally, 0.95 f 0.04. The range of uncertainty indicated here is meant to include statistical uncertainty as well as the effect of possible systematic errors. Data for @,,, and $,, for an extended stability range (1 > c > -3) are presented. Several formulas for &, and $,, appearing in the literature have been used in a comparative study. But 6rst all the formulas have been modified in accordance with the following assumptions: k = 0.40 and ($,Jc-c = 0.95; deviations from this result in the various studies are due to incomplete correction for flow distortion. After new corrections are introduced, the various formulas were compared with the present measurements and with each other.

Some of the fundamental issues of surface layer meteorology are critically reviewed. For the von Karman constant (Ic), values covering the range from 0.32 to 0.65 have been repotted. Most of the data are, however, found in a rather narrow range between 0.39 and 0.4 1. Plotting all available atmospheric data against the so-called roughness Reynolds number, Rq, = U+Z~/Y or against the surface Rossby number, Roa = G/f .zo gives no clear indication of systematic trend. It is concluded that k is indeed constant in atmospheric surface-layer flow and that its value is the same as that found for laboratory flows, i.e. about 0.40.Various published formulae for non-dimensional wind and temperature profiles, &, and tih respectively, are compared after adjusting the fluxes so as to give k = 0.40 and (dh/&)z,L=O = 0.95. It is found that for Iz/LI 2 0.5 the various formulae agree to within lO-20%. For unstable stratification the various formulations for ~$h continue to agree within this degree of accuracy up to at least z/L z -2. For drn in very unstable conditions results are still conflicting. Several recent data sets agree that for unstable stratification Ri M lSz/ L up to at least -z/L = 0.5 and possibly well beyond.For the Kolmogorov streamwise inertial subrange constant, (Y ,,, it is concluded from an extensive data set that aU = 0.52 f 0.02. The corresponding constant for temperature is much more uncertain, its most probable value being, however, about 0.80, which is also the most likely value for the corresponding constant for humidity.The turbulence kinetic energy budget is reviewed. It is concluded that different data sets give conflicting results in important respects, particularly so in neutral conditions. It is demonstrated that the inertial-subrange method can give quite accurate estimates of the fluxes of momentum, sensible heat and water vapour from high frequency measurements of wind, temperature and specific humidity alone, provided 'apparent' values of the corresponding Kolmogorov constants are used. For temperature and humidity, the corresponding values turn out to be equal to the 'true' constants, so PA M p Z 0.80. For momentum, however, the apparent constant (Y,A z 0.60. * Based on an invited paper presented at

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, appearing abruptly at wave age co/Uw equal to 1.2. Turbulence spectra of the horizontal components were shown not to scale with height above the water surface, in contrast to vertical velocity spectra for which such a variation was observed in the low-frequency range. In addition, spectral peaks in the horizontal wind spectra were found at a frequency as low as 10 -3 Hz. From a comparison with results from a previous study it was concluded that this turbulence is of the "inactive" kind, being brought down from the upper parts of the boundary layer by pressure transport.

[1] On the basis of an extensive data set from the air-sea interaction station Ö stergarnsholm in the Baltic Sea, the dependence of drag on the ocean of wave state parameters has been studied for near-neutral conditions. For developing sea, the drag depends on wave age, u * /c p (u * friction velocity and c p the phase speed of the dominant waves), in agreement with recent findings over the World Ocean, strongly supporting that the Ö stergarnsholm station can be relied upon to give results representative of open ocean conditions. For such conditions, it is demonstrated that the logarithmic wind law is indeed valid. For mixed sea/swell the logarithmic wind law is not valid and the drag coefficient, C D depends on two parameters representing the wave state: u * /c p and E 1 /E 2 , where E 1 is the energy of the relatively long waves (having a phase velocity larger than the wind speed at 10 m) and E 2 , the short wave energy. Thus, plotting C D as a function of u * /c p gives a clear ordering of the data in parallel, sloping bands according to the value of E 1 /E 2 . Thus, whereas very young and slow waves affect the atmospheric flow similar to rigid roughness elements, with the occurrence of longer waves, an entirely different mechanism gains successively more importance and dynamical coupling with the atmospheric turbulence occurs. It may be speculated that the often observed kink in the wind profile represents the upper bound of a wave-boundary-layer, which is thus an order of magnitude deeper than predicted and observed during growing sea conditions.

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