An efficient way of contrasting model behavior is to devise an efficient set of process-oriented test problems in which alternative numerical formulations can be assessed against standards of merit (cost, accuracy, robustness, most smooth solution, etc). Several types of process-oriented test cases are posted on this web site. Analytical or semi-analytical solutions exist for all these problems, and they form the basis for model comparison. This approach has proven useful in atmosphere models (Williamson et al., 1992) and ocean models (Haidvogel and Beckmann, 1999).