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461.
The spectral global baroclinic primitive equation model described in Part I of this paper has been extensively tested. The model has been run daily from operational analyses for over a year. From this large sample of forecasts, verification statistics have been collected and compared with similar statistics collected from three competitive grid‐point models. The spectral model is also compared with the grid‐point models in a synoptic case study. A second case study demonstrates the effect of horizontal resolution and physical effects on spectral model forecasts. The results of these experiments demonstrate that the spectral model is highly competitive with other models, in terms of both accuracy and computational efficiency. On 18 February 1976 the spectral model became the operational Canadian large‐scale forecast model. 相似文献
462.
The NCEP twentieth century reanalyis and a 500-year control simulation with the IPSL-CM5 climate model are used to assess the influence of ocean-atmosphere coupling in the North Atlantic region at seasonal to decadal time scales. At the seasonal scale, the air-sea interaction patterns are similar in the model and observations. In both, a statistically significant summer sea surface temperature (SST) anomaly with a horseshoe shape leads an atmospheric signal that resembles the North Atlantic Oscillation (NAO) during the winter. The air-sea interactions in the model thus seem realistic, although the amplitude of the atmospheric signal is half that observed, and it is detected throughout the cold season, while it is significant only in late fall and early winter in the observations. In both model and observations, the North Atlantic horseshoe SST anomaly pattern is in part generated by the spring and summer internal atmospheric variability. In the model, the influence of the ocean dynamics can be assessed and is found to contribute to the SST anomaly, in particular at the decadal scale. Indeed, the North Atlantic SST anomalies that follow an intensification of the Atlantic meridional overturning circulation (AMOC) by about 9 years, or an intensification of a clockwise intergyre gyre in the Atlantic Ocean by 6 years, resemble the horseshoe pattern, and are also similar to the model Atlantic Multidecadal Oscillation (AMO). As the AMOC is shown to have a significant impact on the winter NAO, most strongly when it leads by 9 years, the decadal interactions in the model are consistent with the seasonal analysis. In the observations, there is also a strong correlation between the AMO and the SST horseshoe pattern that influences the NAO. The analogy with the coupled model suggests that the natural variability of the AMOC and the gyre circulation might influence the climate of the North Atlantic region at the decadal scale. 相似文献
463.
Abdelilah Dekayir Marc Amouric Juan Olives Claude Parron Abdelilah Nadiri Abdelkader Chergui M.Abdeljalil El Hajraoui 《Comptes Rendus Geoscience》2004,336(12):1061-1070
In Volubilis, Roman mosaics are very beautiful and reveal, from the bottom to the surface, three layers: (i) ‘hedgehog’ layer, (ii) coarse grain mortar layer (rudus + nucleus) and (iii) tesselatum. Mineralogical analysis of coarse grain mortar sampled in Flavius Germanus mosaic shows that it consisted of quartz and calcite, with some feldspar and probably mica and dolomite. Fine-grained mortar in tesselatum is made from a mixture of calcite and quartz only. Limestone tesserae (white, pink and brown) show petrographic facies that change from micritic to oolithic limestone. Conversely, black and brick red tesserae are respectively made of marble, red sandstone and from fire clay. Other colours as yellow, blue, green and grey are obtained from artificial glass with different chemical compositions. To cite this article: A. Dekayir et al., C. R. Geoscience 336 (2004). 相似文献
464.
Hugues Leroux Jean Claude Doukhan Falko Langenhorst 《Physics and Chemistry of Minerals》1994,20(8):521-530
Transmission electron microscopy was used for characterizing the defect microstructure induced by shock experiments in a single crystal of diopside. The shock-induced defects found in the crystal can be divided in four distinct types:
- A high density and pervasive distribution of dislocations in glide configuration (glide systems (100)[0
- Mechanical twin lamellae, mostly parallel to (100), the (001) twin lamellae are less abundant. li]3)
- Heterogeneously distributed tiny molten zones (3 to 20 μm size) which, after cooling, appear as a glass with a chemical composition very close to the one of the original diopside.