A MULTICOMPONENT DECOMPOSITION OF SPATIAL RAINFALL FIELDS .2. SELF-SIMILARITY IN FLUCTUATIONS

In the first paper (Kumar and Foufoula-Georgiou, this issue) we develo ped a methodology for the segregation of large- and small-scale featur es (fluctuations) of spatial rainfall fields. In this paper we develop a framework for testing the presence and studying the nature of self- similarity in the fluctuations. It is found that rainfall fluctuations may be approximated by stable distributions and show scaling up to a certain scale. We define and estimate parameters that characterize the scaling and spatial dependence of the rainfall fluctuations and we us e these parameters, estimated for several radar rainfall frames (in ti me), to relate to and identify the evolutionary nature of rainfall. Tw o radar depicted rainfall fields have been extensively analyzed: a sev ere spring time midlatitude squall line storm and a mild midlatitude w inter type storm. The type of scaling in rainfall fluctuations shows s ignificant variation from one rainfall field to another.