Modeling of the Global Water Cycle - Analytical Models

Both numerical and analytical models of coupled atmosphere and its underlying ground components (land, ocean, ice) are useful tools for modeling the global and regional water cycle. Unlike complex three-dimensional climate models, which need very large computing resources and involve a large number of complicated interactions often difficult to interpret, analytical models are able to provide more direct and intuitive figures of variability and processes in a highly simplified system. They can be a good and efficient alternative modeling tool, especially for studying continental water cycle. This article describes the analytical models developed based on the soil and atmospheric water and energy conservation equations. A fourth-order model is used to illustrate the perturbation equation, solutions, and physical interpretation. Our understanding of some water cycle variability issues, including timescale, persistence, and major physical parameters and processes, obtained from the analytical models is presented.