CONDITIONAL SAMPLING OF COHERENT STRUCTURES IN ATMOSPHERIC-TURBULENCEUSING THE WAVELET TRANSFORM

The development and evaluation of a technique to detect and retrieve c oherent structures embedded in a record of atmospheric surface-layer t emperature fluctuations is described. This new detection scheme, based on a local wavelet transform, is used to conditionally sample the org anized structures from the more random background turbulence. This met hod provides a much needed alternative to the commonly used but not so objective variable interval time averaging. When conditional sampling using the wavelet transform is applied, the series is decomposed into two signals, one with high wavelet coefficients and one with low coef ficients, corresponding to the strong events and to random turbulence of the flow, respectively. A test of the method shows it to be success ful in detecting and retrieving localized structures in a record of te mperature fluctuations.