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Nombre de programmes trouvés : 75
Conférences

le (28m58s)

Modelling Forced and Internal Climate Variability During the Last Millennium

At hemispheric scale, the surface temperature is strongly influenced by the 28 variations of the natural (solar and volcanic) and anthropogenic (land-use, sulphate aerosols, greenhouse gas concentrations) forcings. By contrast, at regional scale, the internal variability, which is purely due to the internal dynamics of the climate system, can mask the forced response. As a consequence, before the 20th century, cold or warm periods are rarely global, homogenous phenomena. Furthermore, the response to the forcing could be associated with changes in the frequency of some modes of variability. This interplay between the response of the climate system to the various ...
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Label UNT Conférences

le (54m24s)

Seismic tomography : A giiant inverse problem

In this talk I shall give an overview of the development of seismic tomography: constructing images of elastic properties in the Earth's interior from seismic observations at its surface. The use of ray-theoretical approximations allows us to image long-wavelength structure. To increase resolution, however, we cannot escape using the wave equation. Modeling the waveforms themselves is highly nonlinear, but the nonlinearity of the problem can be kept under control by using secondary observables such as delays of time- and frequency windowed waveforms. The resulting ...
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