The book is an outcome of the work carried out by the author during the course of his D. Phil. thesis at the University of Allahabad. It demonstrates how the insight gained from studying conceptual low-order models can be used to understand predictability properties of the complex atmosphere-ocean processes. The tools of nonlinear dynamical systems theory are applied to quantify the predictability of the atmosphere. Author hopes that the book shall be of interest to specialists as well as non-specialists of the subject.