The variability of adjoint sensitivity with respect to model physics and basic-state trajectory

Adjoint sensitivity fields have generally been viewed deterministically in the atmospheric science literature. However, uncertainty exists in the components of the adjoint model, such as the physics and the basic-state trajectories used to calculate the sensitivity fields. In this paper, the variability of adjoint sensitivity fields is examined for two collections of trajectories, each valid over a single time window: one supplied by three global operational models, and the other from a regional, operational ensemble Kalman filter system. Adjoint sensitivities are also compared using a dry adjoint and dry basic state, a moist adjoint and moist basic state, and a moist basic state and dry adjoint. The goal of these latter experiments is to explore the differences in mesoscale sensitivity fields with and without moisture, and to examine how sensitivities degrade when adjoint models utilize simplified physics. In all cases, 24-hr sensitivities are produced with a low-level pres