The Estimation of Regional Precipitation Recycling. Part II: A New Recycling Model

A new two-dimensional analytical recycling model is presented. The model may be thought of as a generalization of the existing (mostly Budyko type) models considered in Part I, which incorporates the additional effects of inhomogeneity of the fluxes and the nonparallel flow effects. The model results are given by a general analytical formula for the recycling ratio distribution. This formula may be applied both for theoretical studies of the influence of regional parameters and flow fields on precipitation recycling and for estimating the recycling ratio from observational data. To study the effects of different flow fields in precipitation recycling a decomposition of the two-dimensional flow field into components of pure flow types is used. In addition to the exact results, simple analytical formulas giving lower bounds of the estimates by the new model are obtained for some basic flow fields. The estimates produced by the model are compared with those given by existing recycling models, and the range of validity of those models is discussed in the context of scale dependence of the recycling phenomenon. The results show that, in general, the effects of a nonparallel flow field in precipitation recycling are significant and may result in more than a twofold increase of the recycling ratio. At the same time, the increase in the degree of precipitation recycling differs considerably for different flow fields and also depends on the region's geometry.