Impatti, adattamento e vulnerabilita Le cause e le responsabilita dei cambiamenti climatici sono state trattate sul numero di ottobre della rivista Cda. Approfondiamo l’argomento presentando il documento: “Cambiamenti climatici 2007: impatti, adattamento e vulnerabilita” votato ad aprile 2007 dal secondo gruppo di lavoro del Comitato Intergovernativo sui Cambiamenti Climatici (Intergovernmental Panel on Climate Change). Si tratta del secondo di tre documenti che compongono il quarto rapporto sui cambiamenti climatici.

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Climate Change 2007: Impacts, Adaptation and Vulnerability.

Abstract A two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea. The domain includes a representation of part of Borneo as well as the sea so that the model can simulate the initiation of convection. Also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle. This allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck, which typically occupies several hundred kilometers of the domain. Frank and Cohen's cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area. The major conclusions are: Ice phase processes are important in determining the level of maximum large-scale heating and vertical motion because there is a strong anvil componen...

Numerical study of convection observed during the Winter Monsoon Experiment using a mesoscale two-dimensional model [presentation]

to be done in this area. Face recognition is a problem that scarcely clamoured for attention before the computer age but, having surfaced, has involved a wide range of techniques and has attracted the attention of some fine minds (David Mumford was a Fields Medallist in 1974). This singular application of mathematical modelling to a messy applied problem of obvious utility and importance but with no unique solution is a pretty one to share with students: perhaps, returning to the source of our opening quotation, we may invert Duncan's earlier observation, 'There is an art to find the mind's construction in the face!'.

Linear and nonlinear waves, by G. B. Whitham. Pp.636. £50. 1999. ISBN 0 471 35942 4 (Wiley).

United States. National Oceanic and Atmospheric Administration (Postdoctoral Fellowship Program)

Physically-based Assessment of Hurricane Surge Threat under Climate Change

[1] This paper presents a new, generalized two-phase debris flow model that includes many essential physical phenomena. The model employs the Mohr-Coulomb plasticity for the solid stress, and the fluid stress is modeled as a solid-volume-fraction-gradient-enhanced non-Newtonian viscous stress. The generalized interfacial momentum transfer includes viscous drag, buoyancy, and virtual mass. A new, generalized drag force is proposed that covers both solid-like and fluid-like contributions, and can be applied to drag ranging from linear to quadratic. Strong coupling between the solid- and the fluid-momentum transfer leads to simultaneous deformation, mixing, and separation of the phases. Inclusion of the non-Newtonian viscous stresses is important in several aspects. The evolution, advection, and diffusion of the solid-volume fraction plays an important role. The model, which includes three innovative, fundamentally new, and dominant physical aspects (enhanced viscous stress, virtual mass, generalized drag) constitutes the most generalized two-phase flow model to date, and can reproduce results from most previous simple models that consider single- and two-phase avalanches and debris flows as special cases. Numerical results indicate that the model can adequately describe the complex dynamics of subaerial two-phase debris flows, particle-laden and dispersive flows, sediment transport, and submarine debris flows and associated phenomena.

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A general two-phase debris flow model

The problem of the long wave runup on a beach is discussed in the framework of the rigorous solutions of the nonlinear shallow-water theory. The key and novel moment here is the analysis of the runup of a certain class of asymmetric waves, the face slope steepness of which exceeds the back slope steepness. Shown is that the runup height increases when the relative face slope steepness increases whereas the rundown weakly depends on the steepness. The results partially explain why the tsunami waves with the steep front (as it was for the 2004 tsunami in the Indian Ocean) penetrate deeper into inland compared with symmetric waves of the same height and length.

Runup of nonlinear asymmetric waves on a plane beach

 The main goal of this study is to give the preliminary estimates of the tsunami risks for the Lesser Antilles We investigated the available data of the tsunamis in the French West Indies using the historical data and catalogue of the tsunamis in the Lesser Antilles In total, twenty-four (24) tsunamis were recorded in this area for last 400 years; sixteen (16) events of the seismic origin, five (5) events of volcanic origin and three (3) events of unknown source Most of the tsunamigenic earthquakes (13) occurred in the Caribbean, and three tsunamis were generated during far away earthquakes (near the coasts of Portugal and Costa Rica) The estimates of tsunami risk are based on a preliminary analysis of the seismicity of the Caribbean area and the historical data of tsunamis In particular, we investigate the occurrence of historical extreme runup tsunami data on Guadeloupe, and these data are revised after a survey in Guadeloupe

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Evaluation of tsunami risk in the Lesser Antilles

The problem of the sea wave runup on a beach is discussed in the framework of the rigorous solutions of the nonlinear shallow-water theory. Key and novel moment here is the accounting of the asymmetric waves when the face slope steepness exceeds the back slope steepness. It is shown that the runup height growth with increase of the face slope steepness meanwhile the rundown characteristics are weakly depend from the face slope steepness. These results explain why the tsunami waves with steep front (as during the 2004 tsunami in the Indian Ocean) penetrate inland on large distances to compare with wave with symmetrical shape.

Runup of nonlinear deformed waves on a beach

A major collapse of a lava dome occurred at the Soufriere Hills Volcano (Montserrat, Lesser Antilles), culminating late in the evening (11:35 PM local time) on July 12, 2003 (03:35 GMT on 13 July) This generated a tsunami, which was recorded on Montserrat 2-4 km from the generating area and Guadeloupe, 50 km from Montserrat Results of field surveys are presented Tsunami wave height on Montserrat may have been about 4 m according to the location of a strandline of charred trees and other floating objects at Spanish Point on the east coast of the island The wave height on Guadeloupe according to “direct” witnesses was about 05-1 m at Deshaies and near Plage de la Perle The tsunami at Deshaies caused the scattering of boats as confirmed by fishermen and local authorities Data from the field survey are in agreement with the predicted tsunami scenario obtained by numerical simulation

Tsunami generated by the volcano eruption on July 12-13 at Montserrat, Lesser Antilles

. Tsunami wave generation by submarine landslides of a variable volume in a basin of variable depth is studied within the shallow-water theory. The problem of landslide induced tsunami wave generation and propagation is studied analytically for two specific convex bottom profiles (h ~ x4/3 and h ~ x4). In these cases the basic equations can be reduced to the constant-coefficient wave equation with the forcing determined by the landslide motion. For certain conditions on the landslide characteristics (speed and volume per unit cross-section) the wave field can be described explicitly. It is represented by one forced wave propagating with the speed of the landslide and following its offshore direction, and two free waves propagating in opposite directions with the wave celerity. For the case of a near-resonant motion of the landslide along the power bottom profile h ~ xγ the dynamics of the waves propagating offshore is studied using the asymptotic approach. If the landslide is moving in the fully resonant regime the explicit formula for the amplitude of the wave can be derived. It is demonstrated that generally tsunami wave amplitude varies non-monotonically with distance.

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Narcisse Zahibo

Papers

Runup of nonlinear asymmetric waves on a plane beach

Evaluation of tsunami risk in the Lesser Antilles

Runup of nonlinear deformed waves on a beach

Tsunami generated by the volcano eruption on July 12-13 at Montserrat, Lesser Antilles

Tsunami waves generated by submarine landslides of variable volume: analytical solutions for a basin of variable depth