A DYNAMIC AND SPATIAL SCALING APPROACH TO ADVECTION FORECASTING

摘要

SPROG is an advection based nowcasting system that exploits the observation that rain fields commonly exhibit both spatial and dynamic scaling dependent properties i.e. the lifetime of a feature in the field is on the scale of the feature (large features evolve more slowly than small features) and that features at all scales between the outer and inner observed scales are present in the field. A Fourier notch filter is used to disaggregate the rain field into a multiplicative hierarchy or cascade of fields, where each level in the cascade represents features in the rain field at a particular scale. The Lagrangian temporal evolution of each level in the cascade is modelled using a simple autoregressive (lag two) model, which automatically causes the forecast field to become smooth as the structures at the various scales evolve through their life times