Abstract
The experimentally observed probability distribution of the acoustic echo-signal intensity associated with the temperature structure parameter C 2T was found to be markedly non-lognormal in the convective boundary layer. A two-regime model of thermal turbulence is suggested that combines a small-scale turbulence description with the concept of coherent structures. The probability density function of the logarithm of the temperature structure parameter C 2T is assumed to be approximated by a combination of two normal distributions taken with corresponding weights. It can be interpreted as the existence of two regimes of thermal turbulence, namely, light background turbulence and strong turbulence within convective plumes. This decomposition of the probability density function into ‘plume’ and ‘background’ parts provides an objective procedure for separating the statistics of these two regimes as well as to determine the probability of convective plume occurrence. It is shown that the conventionally measured overall mean C 2T , averaged over a long enough time interval, is determined mainly by the probability of plume occurrence, while the mean C 2T value within plumes changes slightly. The decrease of the total mean C 2T with height is caused mainly by the decrease of the probability of the plume occurrence with height.
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Petenko, I.V., Shurygin, E.A. A Two-Regime Model For The Probability Density Function Of The Temperature Structure Parameter In The Convective Boundary Layer. Boundary-Layer Meteorology 93, 381–394 (1999). https://doi.org/10.1023/A:1002015522817
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DOI: https://doi.org/10.1023/A:1002015522817