COMPARISON OF INITIAL AND LATERAL BOUNDARY-CONDITION SENSITIVITY FOR A LIMITED-AREA MODEL

The sensitivities of two forecast aspects with respect to perturbation s of initial and lateral boundary conditions are determined using an a djoint of a limited-area model. Sensitivities are presented as gradien t fields. Some characteristics of the sensitivity fields have simple d ynamical explanations, such as their strong dependence on winds, and d o not require an adjoint model to reveal them. Other characteristics w ould be difficult to ascertain without an adjoint model, although they , too, in retrospect, have simple dynamical explanations. Still others , although equally important and undoubtedly dependent on the dynamics , would be practically impossible to determine without an adjoint. The quantity and quality of information provided by the adjoint solutions render the adjoint model a tool that is indispensable for sensitivity analysis.