Simple scaling anisotropy in the atmosphere, an exploratory study

Motivation: we investigate scaling anisotropy in cloud images. Even if these images look much the same in all directions, we can observe anisotropic structure at different scales. Scaling anisotropy measurement method: we propose a simple method to visualize and measure basic exponents of scaling anisotropy in all directions, assuming weak anisotropy. MODIS satellite images are used to measure scaling anisotropy on cloud fields. Main results: a smooth variation of the structure function exponent with the geographic direction has been observed and the behaviour of the function corresponds to what is mathematically expected. There is also a clear difference between the exponents in the North-South and East-West directions. The variation in the value of the exponent between the two axes is one quarter of the exponent, with a higher exponent in the East-West axis.