The Inclusion of 3D Prognostic Cloud and Precipitation Variables in Adjoint Calculations

The potential of the inclusion of two prognostic variables for cloud condensate and precipitation content in adjoint calculations has been investigated in the framework of Météo-France's operational spectral global model, ARPEGE. The tangent linear and adjoint versions of the recently developed explicit large-scale cloud and precipitation scheme have been coded and tested. In particular, the validity of the linear hypothesis has been checked when finite-size perturbations are applied to the initial model state vector. Then, the new explicit cloud and precipitation scheme and its adjoint version have been integrated in a set of sensitivity experiments. These allowed the assessment of the relative impacts of initial perturbations imposed on each model variable on the variations of various meteorological aspects of the forecast that relate either to the dynamics or to the cloud and precipitating activity of some extratropical cloud systems.