A wavelet-based method for multifractal image analysis. III. Applications to high-resolution satellite images of cloud structure

We apply the 2D wavelet transform modulus maxima (WTMM) method to high-reso lution LANDSAT satellite images of cloudy scenes. The computation of the ta u(q) and D(h) multifractal spectra for both the optical depth and the radia nce fields confirms the relevance of the multifractal description to accoun t for the intermittent nature of marine stratocumulus clouds. When assistin g the 2D WTMM method by the wavelet based deconvolution method designed to compute the self-similarity kernel, we show that our numerical tools are ve ry efficient to disentangle the anisotropic texture induced by the presence of convective rolls from the background radiance fluctuations which are li kely to display isotropic scale invariance. Moreover, this analysis reveals that with the available set of experimental data, there is no way to discr iminate between various phenomenological cascade models recently proposed t o account fur intermittency and their log-normal approximations. When furth er investigating the "two-point" space-scale correlation functions, we brin g definite proof of the existence of an underlying multiplicative structure from an "integral" coarsest scale which is given by the characteristic wid th of the convective patterns. We emphasize the log-normal random W-cascade model on separable wavelet orthogonal basis introduced in paper II (N. Dec oster, S.G. Roux, A. Ameodo, Fur. Phys. J. B 15, 739 (2000)), as a very att ractive model (at least as: compared to the models commonly used in the lit erature) of the cloud architecture. Finally, we comment on the multifractal properties of marine stratocumulus radiance fields comparatively to previo us experimental analysis of velocity and temperature fluctuations in high R eynolds number turbulence.