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A contribution to the problem of modelling the dispersion of pollutants in a time-varying, height-structured atmospheric boundary layer
No full textOn breakdowns of the Westerlies
No full textThe transition of the middle-latitude atmospheric circulation from “zonal” to “meridional” type is known to occur in connection with the growth of local disturbances characterized by a very low mobility. This process is very frequent over Europe, where it leads usually to a blocking situation. In this paper, the physical conditions that determine the growth and the motion of localized disturbances (wave packets) in a rotating (β-plane) westerly flow are analysed for various mechanisms of instability. The results are discussed in the light of what is known from available data
Local Multiple equilibria and Regional Atmospheric Blocking
No full textStationary flow of a barotropic fluid in a β channel has been shown by Charney and De Vore (1979) to possess multiple-equilibrium solutions when sinusoidal topographic forcing is exerted within the region of resonance near the wavenumber of stationary Rossby waves, and nonlinear effects are taken into account. Charney and De Vore associate the different solutions with zonal and blocking states of global circulation. However, real topography is non-sinusoidal and, most of the time, observed blocking configurations display a pronounced regional character. On the other hand, the problem of superimposing different harmonics is made difficult here by the essential role played by nonlinearity in the theory of multiple equilibria.
In this paper, the mathematical problem of determining the stationary states of flow of barotropic fluid in a β plane when topography is nonsinusoidal is analyzed with the help of the perturbative assumptions that the latitudinal scale of the flow is very large and topography has the form of a slowly modulated sinusoid.
The multiple states of stationary flow described by Charney and De Vore are found to exist simultaneously in different regions of the β plane. Theoretical solutions corresponding to different kinds of resonant forcing are analyzed.
The theoretical solutions are discussed in relationship to the problem of blocking as a “regional” phenomenon and are shown to have several different features in common with observed persistent blocking patterns
The effect of the boundary conditions on the simulation of the 4 November 1966 storm over Italy.
No full textAdvances in Geoscience
Hydrological verification of ECMWF and Limited Area Model simulations for the November 1966 catastrophic floods in Italy (Florence and Eastern Alps)
No full textExtended Abstract, Pubblications of Meteoswiss n°6
Previsioni di piena mediante un modello idrologico e un modello meteorologico ad area limitata: alcune esperienze applicative durante l'esperimento MAP-SOP
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