Sensitivity of high resolution forecasts using the adjoint technique at the 10 km scale
Sensibilité des prévisions à haute résolution, utilisant la technique de l'adjoint à l'échelle 10 km
Soci, C. ; Fischer, C. ; Horanyi, A.
ABSTRACT
This paper provides an experimental framework designed to assess the performance and the evolution of<br>the diabatic Aire Limitée Adaptation Dynamique Développement International (ALADIN) adjoint model<br>at 10-km grid size. Numerical experiments are carried out with the goal of evaluating the adjoint model<br>solutions and the benefit of employing a complex linearized physical parameterization package in the<br>gradient computation. Sensitivity studies with respect to initial conditions at high resolution on real meteorological<br>events are performed. Numerical results obtained in the gradient computations show that, at<br>high resolution, a strong nonlinear flow over complex orography might be a potential source of numerical<br>instability in the absence of a robust dissipative physics employed in the adjoint model. Also, the scheme<br>of the linearized large-scale precipitation is a source of noise in precipitating areas. The results on one<br>particular case suggest that on the one hand the adjoint model is able to capture the dynamically sensitive<br>area, but on the other hand the subsequent sensitivity forecast is more sensitive to the sign and the<br>amplitude of the initial state perturbation rather than the structure of the gradient field.<br>
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