Turbulent transfer mechanisms in the atmospheric surface layer

Abstract

The objective of this study was to investigate the turbulent transfer mechanism near the surface. ‘Direct’ measurements of the turbulent fluxes of momentum, heat, and moisture were made in the atmospheric surface layer 2 m above a grass surface at Ladner, Canada. The spectral correlation coefficients were considered to be a measure of the transfer efficiency as a function of scale size. For momentum transfer the efficiency decreased at all scales as instability increased. It is postulated that this was due to greater amounts of momentum being transferred in bursts of short duration, thus making the spectral correlation coefficient, averaged over sufficient time, smaller. The Ladner results for heat transfer showed that its transfer efficiency increased at all scales when instability increased. The ratio of the transfer efficiency of heat to that of momentum was greater than 1 for most scales, even for near neutral stratifications, and increased to between 2 and 3 for more unstable conditions. The efficiency of moisture transfer was usually smaller than that for heat transfer and was found to depend on the correlation between moisture fluctuations and those of temperature.

Turbulent transport processes of momentum and sensible heat in the surface layer over a paddy field

“…The correlation coefficient I,,,~ is positive in the unstable regime and increases with increasing instability, visible in spite of large scatter. The dependency of correlation coefficients r,, and r,,,, on the stability parameter -(z -d)/L agrees fairly well with the results of Haugen et al (1971), McBean and Miyake (1972), , and Takeuchi et al (1980). The dependency of correlation coefficients r, .…”

“…+ 2.5 (for daytime conditions). Thus, some of the flux may have been lost as noted by McBean and Miyake (1972). A correction was not made in the following anaIysis.…”

Latent and sensible heat flux predictions from a uniform pine forest using surface renewal and flux variance methods

“…Some dissimilarity between heat and water vapour fluctuations (Q') at large wavermmbers was also reported in the study by Katul and Parlange (1994) for a uniform bare soil site. Measurements presented by McBean and Miyake (1972) above a grass su&ace at Ladner in Canada also suggests that the efficiency of moisture transfer from the ground surface is strongly dependent on &Q, (see also Busch, 1973). Measurements by Lang et al (1983) demonstrate that the ratio of eddy diffusivities for T and q is different for advective conditions suggesting a dissimilarity between T and Q.…”

Pressure and humidity effects on optical refractive-index fluctuations

“…The correlation req ranged between 0.3 and 0.9 except for the one case already noted where it was negative (roq = -0.3). McBean and Miyake (1972) postulated that the correlation between 8 and 4 depended on surface and mesoscale conditions and should not be assumed to be unity in all cases. Over the ocean req varies in the vertical with values between 0.6 and 0.9 for r/Zi < 0.1, then decreasing to become negative in the upper half of the boundary layer (Wyngaard et al, 1978) (Zi is height of the boundary layer).…”