Simplified and Regular Physical Parameterizations for Incremental Four-Dimensional Variational Assimilation

A set of physical parameterizations has been developed for inclusion in incremental four-dimensional variational assimilation (4D-Var). The goal for this physical package is that it be simple, regular (for the efficiency of the minimization in 4D-Var), and at the same time realistic enough. The package contains a simplified computation of radiative fluxes, vertical turbulent diffusion, orographic gravity waves, deep convection, and stratiform precipitation fluxes. Its tangent-linear and adjoint counterparts have also been developed. The validations of the simplified physical parameterizations and of the tangent-linear model with those included have been done. The importance of regularization (removing some thresholds in physical parameterizations that can affect the range of validity of the tangent-linear approximation), which arises during validation of the tangent-linear model, is assessed.