Adjoint Sensitivity with a Nested Limited Area Atmospheric Model

Abstract

A one-way interactive nesting capability was added to the tangent linear and adjoint models of a limited area atmospheric forecasting system. In the tangent linear model , perturbation information is passed through the lateral boundaries to higher resolution nests. Gradient information moves through the lateral boundaries in the direction of the lower resolution parent domains in the adjoint model. The system was demonstrated by forcing the adjoint model over a small volume resolved on the finest nest and constructing optimal perturbations from the gradient information on the parent domain. Small perturbations (<1 m s\(^{-1}\) in wind speed) on the coarsest domain resulted in relatively large changes in the boundary layer flow over the localized area on the finest scale nest where the adjoint model was originally forced.