Prediction of monsoon rainfall with a nested grid mesoscale limited area model     

S. K. Roy Bhowmik 《Journal of Earth System Science》2003,112(4):499-519

At the India Meteorological Department (IMD), New Delhi, a 12-level limited area model with 100 km horizontal resolution has been in use for weather forecasting. The present study uses this model together with a higher horizontal resolution (50 km) and vertical resolution (16-levels) model to examine the impact of increased resolution to simulate mesoscale features of rainfall during monsoon disturbances. The model was run for 22 days in the month of August 1997 and one week in September 1997 during three monsoon depressions and one cyclonic storm in the Bay of Bengal. The model results are compared with observations. The study shows that the model can capture mesoscale convective organization associated with monsoon depression.  相似文献   

Motion of the Scotia Sea plates   总被引：2，自引：0，他引：2  

Christine Thomas  Roy Livermore  Fred Pollitz 《Geophysical Journal International》2003,155(3):789-804

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Seyfert galaxies and the radio–far-infrared correlation     

A. L. Roy    R. P. Norris    M. J. Kesteven    E. R. Troup  & J. E. Reynolds 《Monthly notices of the Royal Astronomical Society》1998,301(4):1019-1030

We have observed a sample of 149 Seyfert galaxies and radio-quiet quasars at 13 cm with both a 275-km radio interferometer and the 6-km compact array of the Australia Telescope. The high-resolution observations searched for the presence of compact, high-brightness-temperature radio emission from the active nucleus. The low-resolution observations measured the total radio emission from the galaxy disc and Seyfert core and lobes. From these we draw the following conclusions. (i) Seyfert galaxies that lack compact radio cores display a correlation between radio and far-infrared (FIR) emission similar to the correlation displayed by normal spirals, albeit with greater scatter. The correlation is found to be intrinsic and is not an artefact of the richness effect. (ii) A very different radio–FIR correlation is displayed by those Seyferts that harbour compact radio cores. These tend to be more radio-loud than either normal spirals or the Seyferts that lack compact cores. The compact core emission thus seems to be responsible for the generally poor radio–FIR correlation displayed by Seyfert galaxies. (iii) The radio–FIR correlation is not significantly improved by subtracting off the 0.1-arcsec (20- to 200-pc) compact radio emission from the total radio emission. This suggests that the emission from the active galactic nucleus has significant structure on scales larger than 0.1 arcsec. Perhaps these structures are the 'linear' radio features that have been seen previously in Seyfert nuclei.  相似文献   

Technical Note Characteristics of ground vibrations and structural response to surface and underground blasting     

Pijush Pal Roy 《Geotechnical and Geological Engineering》1998,16(2):151-166

The author considers the structural response of various types of surface structures along with their resonance characteristics as well as magnification and attenuation problems. Experimental data from 20 different mines in India, are compiled and analysed to develop simple general equations for use in field conditions. Interpretation of low frequency waves and their active role in enhancing damage probability of structures is also discussed. Particular situations are examined where low and high dominant band frequencies could obtain. It is suggested that a response analysis be undertaken before establishing damage threshold values of any type of structure. © Rapid Science Ltd. 1998  相似文献   

Young Students' Conceptions of the Marine Environment and Their Role in the Development of Aquaria Exhibits   总被引：1，自引：0，他引：1  

Roy Ballantyne 《GeoJournal》2004,60(2):159-163

Informal learning settings such as aquaria are well-placed to help young students understand the nature and importance of marine environments. In order to achieve this, it is important to incorporate pedagogical principles into exhibit design. Using a constructivist perspective, this paper explores young students' conceptions of the marine environment. The findings indicate that although students are interested in marine life and are familiar with terms such as currents, tides and waves, their understanding of these concepts is limited and confused. It is suggested that by addressing children's limited conceptions in their exhibits and educational programmes, aquaria can foster an understanding of the environmental processes that support marine life, thus contributing to habitat conservation and species survival. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Shear wave anisotropy beneath the Cascadia subduction zone and western North American craton   总被引：3，自引：0，他引：3  

Claire A. Currie  John F. Cassidy  Roy D. Hyndman  Michael G. Bostock 《Geophysical Journal International》2004,157(1):341-353

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A graphical approach to polar paths: Paleomagnetic cycles and global tectonics     

W.A. Morris  P.W. Schmidt  J.L. Roy 《Physics of the Earth and Planetary Interiors》1979,19(1):85-99

Some problems of the conventional “minimum polar distance” approach to Precambrian pole path construction are discussed. An alternative technique, based on a less restricted approach, is proposed and assessed by using all presently-available Precambrian and Paleozoic data from the world. In the construction of any pole path, assumptions are always made on the shape of the path through regions of apparently missing data. Many different assumptions are possible. Assuming that the Precambrian tectono-stratigraphic record conforms to repeated sequences of geological events suggests we should observe cycles in the paleomagnetic data. Empirically, it is found that the pole paths for the periods Cambrian-Devonian, and 750–1000 Ma, define cycles of pole motion from equator, up to and over the pole, and back down to the equator. Similar cycles of 250-Ma periodicity can be identified in paleomagnetic data back to 2500-Ma. Global wide changes in the phase of the cycles appears to be coincident with the major subdivisions of geological time i.e., Phanerozoic + Hadrynian, Helikian, Aphebian, and Archean. Finally, the geological implications of these cyclic changes in Precambrian pole paths are briefly discussed.  相似文献   

Isotopic anomalies of noble gases in meteorites and their origins—III. LL-chondrites     

Leo Alaerts  Roy S Lewis  Edward Anders 《Geochimica et cosmochimica acta》1979,43(9):1399-1415

Nine LL-chondrites were studied by a selective etching technique, to characterize the noblegas components in three mineral fractions: HF-HCl-solubles (silicates, metal, troilite, etc.; comprising ～ 99% of the meteorite), chromite and carbon (～ 0.3–0.7%) and Q (a poorly characterized mineral defined by its solubility in HNO₃, comprising ～ 0.05% of the meteorite but containing most of the Ar, Kr, Xe and a neon component of ${}^{20}\text{Ne}{}^{22}\text{Ne}\text{= 10.9 ± 0.8}$). The ${}^{20}\text{Ne}{}^{36}\text{Ar}$ ratio in Q falls wi petrologic type and rising ³⁶Ar content, as expected for condensation from a cooling solar nebula, but contrary to the trend expected for metamorphic losses. Chondrites of different petrologic types therefore cannot all be derived from the same volatile-rich ancestor, but must have formed over a range of temperatures, with correspondingly different intrinsic volatile contents.The CCFXe (carbonaceous chondrite fission) component varies systematically with petrologic type. The most primitive LL3s (Krymka, Bishunpur, Chainpur) contain substantial amounts of CCFXe in chromite-carbon, enriched relative to primordial Xe as shown by high ${}^{136}\text{Xe}{}^{132}\text{Xe}$ (0.359–0.459, vs 0.310 for primordial Xe). These are accompanied by He and by Ne with ${}^{20}\text{Ne}{}^{22}\text{Ne}\text{≈ 8.0}$ and by variable amounts of a xenon component enriched in the light isotopes. The chromite in these meteorites is compositionally peculiar, containing substantial amounts of Fe(III). These meteorites, as well as Parnallee (LL3) and Hamlet (LL4) also contain CCFXe in phase Q, heavily diluted by primordial $\text{Xe}\text{(}{}^{136}\text{Xe}{}^{132}\text{Xe}\text{= 0.317–0.329)}$. On the other hand, LL5s and 6s (Olivenza, St. Séverin, Manbhoom and Dhurmsala) contain no CCFXe in either mineral. This deficiency must be intrinsic rather than caused by metamorphic loss, because Q in these meteorites still contains substantial amounts of primordial Ne.If CCFXe comes from a supernova, then its distribution in LL-chondrites requires three presolar carrier minerals of the right solubility properties, containing three different xenon components in certain combinations. These minerals must be appropriately distributed over the petrologic types, together with locally produced Q containing primordial gases, and they must be isotopically normal, in contrast to the gases they contain. On the other hand, if CCFXe comes from fission of a volatile superheavy element, then its decrease from LL3 to LL6 can be attributed to progressively less complete condensation from the solar nebula. Ad hoc assumptions must of the host phase Q, its association with ferrichromite and the origin of the associated xenon component enriched in the light isotopes.Soluble minerals in LL3s and LL4s contain a previously unobserved, solar xenon component, which, however, is not derived from the solar wind. Three types of ‘primordial’ xenon thus occur side-by-side in different minerals of the same meteorite: strongly fractionated Xe in ferrichromite and carbon, lightly fractionated Xe in phase Q, and ‘solar’ Xe in solubles. Because the first two can apparently be derived from the third by mass fractionation, it seems likely that all were trapped from the same solar nebula reservoir, but with different degrees of mass fractionation.  相似文献   

The ambient environment of the Gangetic sediments of chalcolithic period     

D P Agrawal  M N Deshpande  S N Rajaguru  Bhaskar Roy 《Journal of Earth System Science》1978,87(3):23-28

There is considerable controversy regarding the mode of deposition of the OCP culture-associated sediments in the Gangetic valley and their ecological implications. SEM and sedimentologic studies show a fluvial mode of deposition of sediments originally derived from a glacial environment.  相似文献   

Decomposition of hydroxy amino acids in foraminiferal tests; kinetics,mechanism and geochronological implications     

Jeffrey L. Bada  Ming-Yung Shou  Eugene H. Man  Roy A. Schroeder 《Earth and Planetary Science Letters》1978,41(1):67-76

The diagenesis of the hydroxy amino acids serine and threonine in foraminiferal tests has been investigated. The decomposition pathways of these amino acids are complex; the principal reactions appear to be dehydration, aldol cleavage and decarboxylation. Stereochemical studies indicate that the α-amino-n-butyric acid (ABA) detected in foraminiferal tests is the end product of threonine dehydration pathway. Decomposition of serine and threonine in foraminiferal tests from two well-dated Caribbean deep-sea cores, P6304-8 and -9, has been found to follow irreversible first-order kinetics. Three empirical equations were derived for the disappearance of serine and threonine and the appearance of ABA. These equations can be used as a new geochronological method for dating foraminiferal tests from other deep-sea sediments. Preliminary results suggest that ages deduced from the ABA kinetics equation are most reliable because “species effect” and contamination problems are not important for this nonbiological amino acid. Because of the variable serine and threonine contents of modern foraminiferal species, it is likely that the accurate age estimates can be obtained from the serine and threonine decomposition equations only if a homogeneous species assemblage or single species sample isolated from mixed natural assemblages is used.  相似文献