In order to establish the relations between different scale rainfall fields, a space-time multifractal analysis on Doppler radar rainfall from HUBEX was proposed and scaling anisotropy parameters were estimated by spectral analysis. The results indicated that space-time rainfall can be considered to be a self-similar multifractal process approximately.The advection velocities of rainfall fields estimated through tracking techniques were adopted to rescale the time dimension to space dimension.The log-Poisson distribution with two parameters was used as stochastic cascade generator,and the multifractal rainfall space-time downscaling model was developed based on stochastic cascade.The relations between parameters of the log-Poisson distribution and rainfall intensity on larger scale and the coefficient of variation of rainfall fields was studied, and the characteristics of simulated rainfall fields through downscaling model was compared with the radar observed rainfall fields. The results showed that the simulated rainfall fields match scaling behaviors and preserve characteristic properties very well with those for the observed rainfall fields.
