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Predictability of convective systems by numerical models is limited by the rapidly evolving non-hydrostatic dynamics and by the strong non-linearities present in moist thermodynamic processes.
The system under consideration is the convection-resolving, non-hydrostatic atmospheric model MOLOCH, running at about 2.3 km resolution over northern Italy, including an Alpine area and portions of both the Ligurian Sea and the Adriatic Sea. A perturbation breeding technique is used to estimate the local unstable structures that characterize the dynamic growth of small perturbations and errors. The non-linear evolution of states perturbed by organized bred vectors is studied and the growth of perturbations is characterized by estimating the growth exponent and the doubling time. Linearity indicators (proposed by Hohenegger et al., 2006) are computed to estimate the time period of validity of the tangent linear approximation along the non-linear evolution. |
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