FRACTAL PROPERTIES OF TEMPERATlTRE FLUCTUATIONS IN THE CONVECTIVE SURFACE LAYER

Abstract. Temperature fluctuations in a convective surface layer were investigated. Box counting analysis was performed to investigate fractal properties of surfaces of constant temperature and was performed on sets of points obtained by setting thresholds on detrended records. Results indicate that surfaces of constant temperature have fractal properties for thresholds far from the mean. Estimated fractal dinlensions of one-dimensional cuts through these surfaces varied between 0.23 and 0.66, increasing with threshold value approaching the nlean temperature. For thresholds close to the mean, no fractal behavior was found. Asymmetry in results for thresholds above and below the mean temperature was attributed to the asymmetry between updrafts and downdrafts in the convective surface layer. The tenlperature dissipation rate (TD) was also investigated. It was found to be strongly inter mittent with large fluctuations of the intermittency exponent. Moments were analyzed in order to investigate multifractal properties of TD. Results indicate scaling in the range of 50TJ-l OOOTJ (where TJ is the Kolmogorov scale) and multifractal properties resembling those observed for passive scalar dissipation in laboratory flows. 1