2,799 research outputs found
Data Assimilation by Artificial Neural Networks for an Atmospheric General Circulation Model: Conventional Observation
This paper presents an approach for employing artificial neural networks (NN)
to emulate an ensemble Kalman filter (EnKF) as a method of data assimilation.
The assimilation methods are tested in the Simplified Parameterizations
PrimitivE-Equation Dynamics (SPEEDY) model, an atmospheric general circulation
model (AGCM), using synthetic observational data simulating localization of
balloon soundings. For the data assimilation scheme, the supervised NN, the
multilayer perceptrons (MLP-NN), is applied. The MLP-NN are able to emulate the
analysis from the local ensemble transform Kalman filter (LETKF). After the
training process, the method using the MLP-NN is seen as a function of data
assimilation. The NN were trained with data from first three months of 1982,
1983, and 1984. A hind-casting experiment for the 1985 data assimilation cycle
using MLP-NN were performed with synthetic observations for January 1985. The
numerical results demonstrate the effectiveness of the NN technique for
atmospheric data assimilation. The results of the NN analyses are very close to
the results from the LETKF analyses, the differences of the monthly average of
absolute temperature analyses is of order 0.02. The simulations show that the
major advantage of using the MLP-NN is better computational performance, since
the analyses have similar quality. The CPU-time cycle assimilation with MLP-NN
is 90 times faster than cycle assimilation with LETKF for the numerical
experiment.Comment: 17 pages, 16 figures, monthly weather revie
The image of the throne in Ibn Gabirol and the Merkabah mysticism
The subject of the Throne is common to the three abrahamic monotheistic religions and it is an important presence in medieval thought. Specifically in Judaism it has a prominent place, since the first great trend in Jewish mysticism is characterized by the contemplation of the Merkabah (Charriot/Throne) images described from the vision of Prophet Ezekiel. At the same time, many medieval Jewish philosophers also mention the subject. Although the philosophical work of Ibn Gabirol is characterized by the absence of religious references, there is one single passage in the Fons vitae that seems to refer to the Throne. In this article we will try to improve the interpretation of this passage from the Fons vitae by verifying the presence of the Merkabah mystical images in Ibn Gabirol poetry in the light of the indications from the mystical literature and the Jewish imaginary
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