The Regional Ocean Modeling System (ROMS) is a full-featured, well-engineered, production-ready ocean dynamics model provided by a distributed and shared memory parallelized kernel with nesting and restart capabilities.
ROMS is a free-surface, terrain-following, primitive equations ocean model widely used by the scientific community for a diverse range of applications (e.g., Haidvogel et al., 2000; Marchesiello et al., 2003; Peliz et al., 2003; Di Lorenzo, 2003; Dinniman et al., 2003; Budgell, 2005; Warner et al., 2005a, b; Wilkin et al., 2005). The algorithms that comprise the ROMS computational nonlinear kernel are described in detail in Shchepetkin and McWilliams (2003, 2005), and the tangent linear and adjoint kernels and platforms are described in Moore et al. (2004). ROMS includes accurate and efficient physical and numerical algorithms and several coupled models for biogeochemical, bio-optical, sediment, and sea ice applications. The sea ice model is described in Budgell (2005). It also includes several vertical mixing schemes (Warner et al., 2005a), multiple levels of nesting, and composed grids.
The dynamical kernel of ROMS comprises four separate models: nonlinear (NLM), tangent linear (TLM), representative tangent linear (RPM), and adjoint (ADM). Several drivers run each model (NLM, TLM, RPM, and ADM) separately and together.
The drivers shown in the propagator group are used for Generalized Stability Theory (GST) analysis (Moore et al., 2004) to study the dynamics, sensitivity, and stability of ocean circulations to naturally occurring perturbations, errors, or uncertainties in the forecasting system, and adaptive sampling. The driver for adjoint sensitivities (ADSEN) computes the response of a chosen function of the model circulation to variations in all physical attributes of the system (Moore et al., 2006). It includes drivers for strong (S4DVAR, IS4DVAR) and weak (W4DVAR) constraint variational data assimilation (Arango et al., 2006; Di Lorenzo et al., 2006).
A driver for ensemble prediction is available to perturb forcing and/or initial conditions along the most unstable directions of the state space using singular vectors. Finally, several drivers are included in the sanity check group to test the accuracy and correctness of TLM, RPM, and ADM algorithms.
