The Estimation of Regional Precipitation Recycling. Part I: Review of Recycling Models

This review preceding a description of a new recycling model (Part II of this paper) discusses one aspect of the regional precipitation recycling studies, namely, the mathematical modeling of the recycling process. Several recycling models developed in recent decades are discussed within a unified framework of equations of the conservation of atmospheric water vapor mass. Most of the recycling models may be considered as modifications and generalizations of Budyko's model. In spite of different forms, into which authors present their models, every recycling model is based on two equations of conservation of mass for two fractions of precipitable water in the atmosphere—written under some common assumptions—and the equation expressing the condition that these two fractions are well mixed. If any of these three equations is missing the model is incomplete and its results inconsistent. Different models differ by additional assumptions made in order to simplify either the equations or their solution or to circumvent a solution. The unified approach permits the showing of the principles and assumptions that are common to all the models and identify additional assumptions made by a specific model and related limitations. In addition, it makes the derivation of the results more straightforward and frequently less complicated than in the original works.