[Lcefiec] [Coloquios] COLOQUIO EXTRAORDINARIO JUEVES 5/3 13HS AULA A CONFIRMAR: "Space-Time Gaussian fields on spheres of Planet Earth"

[Coloquios CIMA-DCAO]

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                         Coloquio del
  Departamento de Ciencias de la Atmósfera y los Océanos DCAO)/
  Centro de Investigaciones del Mar y la Atmósfera (CIMA)

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JUEVES 5/3 13HS-AULA: A CONFIRMAR!

Space-Time Gaussian fields on spheres of Planet Earth
Emilio Porcu
Universidad Federico Santa Maria
Departamento de Matemáticas
Valparaiso, Chile


We propose stationary covariance functions for processes that evolve 
temporally over a sphere, as well as cross-covariance functions for 
multivariate random fields defined over a sphere. For such processes, 
neither the Euclidean nor the chordal distances are appropriate to 
describe spatial dependences over a sphere. We illustrate several 
methods of construction and provide closed-form expressions for both 
spatio-temporal and multivariate cases. A simulation study assesses the 
discrepancy between the great circle distance, chordal distance and 
Euclidean distance based on map projection both in terms of estimation 
and prediction in a space-time and bivariate spatial setting, where the 
space is in this case the Earth. We revisit the analysis of Total Ozone 
Mapping Spectrometer (TOMS) data and investigate differences in terms of 
estimation and prediction between the aforementioned distance-based 
approaches. Both simulation and real data highlight sensible differences 
in terms of estimation. As far as prediction is concerned, the 
differences can be appreciated only when the interpoint distances are 
large, as demonstrated by an illustrative example.

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Grupo Coloquios
Departamento de Ciencias de la Atmósfera y los Océanos (FCEN-UBA)
Centro de Investigaciones del Mar y la Atmósfera (CONICET-UBA)
Ciudad Universitaria, 2do piso.
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