Impact of background error statistics on 3D-Var assimilation: case study over the Indian region     

V. Rakesh  P. Goswami 《Meteorology and Atmospheric Physics》2011,112(1-2):63-79

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Analysis of buried pipelines subjected to reverse fault motion     

Shantanu Joshi  Amit Prashant  Arghya Deb  Sudhir K. Jain 《Soil Dynamics and Earthquake Engineering》2011

Presently available simplified analytical methods and semi-empirical methods for the analysis of buried pipelines subjected to fault motion are suitable only for the strike-slip and the normal-slip type fault motions, and cannot be used for the reverse fault crossing case. A simple finite element model, which uses beam elements for the pipeline and discrete nonlinear springs for the soil, has been proposed to analyse buried pipeline subjected to reverse fault motion. The material nonlinearities associated with pipe-material and soil, and geometric nonlinearity associated with large deformations were incorporated in the analysis. Complex reverse fault motion was simulated using suitable constraints between pipe-nodes and ground ends of the soil spring. Results of the parametric study suggest that the pipeline's capacity to accommodate reverse fault offset can be increased significantly by choosing a near-parallel orientation in plan with respect to the fault line. Further improvement in the response of the pipeline is possible by adopting loose backfill, smooth and hard surface coating, and shallow burial depth in the fault crossing region. For normal or near normal orientations, pipeline is expected to fail due to beam buckling at very small fault offsets.  相似文献   

Geotechnical properties of the bank sediments along the Dhansiri River channel, Assam     

P. Kotoky  M. K. Dutta  R. Goswami  G. C. Borah 《Journal of the Geological Society of India》2011,78(2):175-183

The bank sediments along the extremely meandered Dhansiri River channel, a south bank tributary of the mighty Brahmaputra River, with erosion potentiality have been investigated to evaluate its certain geotechnical characteristics. The study has shown that the bank sediments are basically composed of CL and ML types of soil. These types of sediments are very much prone to liquefaction which in turn related to erosion susceptibility. The bank stability analysis has differentiated the studied stretch into unstable, at risk and stable zones. Most of the erosion affected zones along the channel reach under study are located within the unstable or at risk zones. The field study around Butalikhowa, Barguriagaon, Golaghat and Duchmuagaon areas along the channel with active erosion activity has supported our contention and practical utility of the present study. It is expected that such type of study will help in providing certain inevitable baseline information for various channel management practices for this extremely flood prone areas of Northeast India.  相似文献   

Floral biodiversity and geology of the Talcher Basin,Orissa, India during the Permian–Triassic interval     

Shreerup Goswami  Kamal Jeet Singh 《Geological Journal》2013,48(1):39-56

The review paper provides an updated account of the previous and recently published records concerning the palaeobiology and the geology of the Talcher Basin of Orissa State, India. We conclude that fossil floral species in this basin originated in the earliest Permian Talchir Formation and evolved and diversified through the Karharbari Fm., Barakar Fm., Barren Measures Fm. and the uppermost Kamthi Fm. (Late Permian–Triassic). The megaflora and the palynology of the different formations of the basin are also discussed briefly. The geological setting of the basin along with the status of different formations (especially the Kamthi Formation) has been redefined. The post‐Barakar Fm. rocks, earlier retained in the Raniganj/Kamthi, Panchet and Mahadeva formations in this basin, have been critically assessed and redefined as the Lower and Upper Kamthi formations of Late Permian and Triassic ages, respectively. Accordingly, the geological map of the basin has been modified. Permian deposits (particularly the Barakar and the lower Kamthi formations) not only have the best preserved flora but also possess the highest diversity, whereas the upper Kamthi Triassic sediments have a meagre number of taxa. The plant diversity of the basin has been discussed in detail to interpret the development of the flora, evolutionary trends and palaeoenvironments of the basin. The patchy Gangamopteris vegetation of the Talchir glacial phase has ultimately evolved and diversified through time (Karharbari Fm. to Lower Kamthi Fm.) and gave rise to the thick dense swampy forests consisting of large Glossopteris trees and other shade‐loving under‐storied pteridophytes. Several groups of plants including spores and pollen have disappeared in a ladder pattern during the Permian–Triassic interval (Lower Kamthi–Upper Kamthi Fm.) and, similarly, in steps, many new fore‐runners appeared in the Upper Kamthi Formation. Records of marine acritarchs and ichnofossils in this basin at various Permian–Triassic levels demonstrate that there were marine influences. These features suggest a paralic (coastal marine to deltaic) mode of origin of the coal beds and associated sediments in the basin. The present study also advocates the continued survival of plants, rather than a mass extinction near the vicinity of the Permian–Triassic (P–T) boundary in this basin. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Granitic basement below Deccan Traps Unearthed by drilling in the Koyna seismic zone, Western India     

Sukanta Roy  N. P. Rao  Vyasulu V. Akkiraju  Deepjyoti Goswami  Mrinal Sen  B. K. Bansal  Shailesh Nayak 《Journal of the Geological Society of India》2013,81(2):289-290

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Simulation of high-impact tropical weather events: comparative analysis of three heavy rainfall events   总被引：1，自引：0，他引：1  

P. Goswami  S. Himesh  B. S. Goud 《Natural Hazards》2013,65(3):1703-1722

Episodes of heavy rainfall, although relatively rare, significantly contribute to the hydrological cycle due to the large quantum of rainfall in a short span of time. Accurate simulation of such heavy or extreme rainfall events therefore is an important benchmark for a model. Here, we consider the simulation of three heavy rainfall events (Mumbai, Bangalore and Chennai) that occurred over the Indian monsoon region in different geographical locations and seasons during 2005, using a mesoscale meteorological model, namely MM5V3. Simulations have been carried out at high resolution (2 km) to resolve orographic features and land–ocean gradients over the event locations with a 3-nest, 2-way configuration. The primary objective of this study is to carry out a multi-event, multi-location evaluation of the model configuration for simulating a class of heavy rainfall events and to compare some important meteorological features of the events. Our results have shown that a very high relative humidity, low-level convergence, convective instability in terms of equivalent potential temperature, high vertical velocity, smaller mixing ratio at low level and higher mixing ratio at upper level essentially dominated and sustained the convective dynamics in all the three events. It was also found that the latent heat flux (LHF) dominated coastal events (Mumbai and Chennai) with relatively much higher values compared to sensible heat flux (SHF) throughout the event life cycle. In the case of the Bangalore event, both LHF and SHF are comparable during the event life cycle.  相似文献   

Nowcasting Bordoichila with a composite stability index     

Sutapa Chaudhuri  Jayanti Pal  Anirban Middey  Sayantika Goswami 《Natural Hazards》2013,66(2):591-607

In operational forecast, the stability indices either individually or in combination are utilized to assess the predictability of local severe storms over a region. The objective of the present study is to identify such stability indices to assess the predictability of Bordoichila of Guwahati, India, during the pre-monsoon season (April–May) aiming to formulate a composite stability index using the most pertinent indices for nowcasting Bordoichila with considerable precision. Bordoichila, meaning the angry daughter of Assam, represents local severe storms of Guwahati during the pre-monsoon season. Precise forecast of Bordoichila is essential to mitigate the associated catastrophe over Guwahati. The forecast quality detection parameters are computed with the available indices during the period from 1997 to 2006 to select the most relevant stability indices for the prevalence of Bordoichila. The method of normal probability distribution is implemented to identify the threshold ranges of the selected indices. The stability indices that are selected with appropriate ranges are lifted index, Showalter index (SI), cross total index (CTI), vertical total index, totals total, convective available potential energy, convective inhibition energy, SWEAT and bulk Richardson number. The forecast skill scores are estimated with the selected indices. The best predictor indices identified for the prevalence of Bordoichila are the cross total index (CTI) and Showalter index (SI). A composite stability index, Bordoichila prediction index, is formulated with CTI and SI with proper weightages. The forecast with BPI is validated with the observations of India Meteorological Department for the year 2007 and is implemented for real-time forecast for the years 2009 and 2011.  相似文献   

Metamorphism of Proterozoic agpaitic nepheline syenite gneiss from North Singhbhum Mobile Belt, eastern India     

Bapi Goswami  Swades Kumar Basu 《Mineralogy and Petrology》2013,107(4):517-538

Sushina nepheline syenite gneisses of Early Proterozoic North Singhbhum Mobile Belt (NSMB), eastern India suffered regional metamorphism under greenschist-amphibolite transitional facies condition. The Agpaitic Sushina nepheline syenite gneisses consist of albite, K-feldspar, nepheline (close to Morozewicz-Buerger composition), aegirine, biotite, epidote, piemontite, sodalite, cancrinite, natrolite and local alkali amphibole. Accessory phases include zircon, hematite, magnetite, rare pyrochlore and occasional eudialyte and manganoan calcic zirconosilicates. Mineral chemistry of albite, K-feldspar, nepheline, aegirine, alkali amphibole, natrolite and zirconium silicate minerals are described. The detailed textural features together with chemical data of some minerals indicate metamorphic overprint of these rocks. A new reaction is given for the genesis of metamorphic epidote. Metamorphic piemontite suggests greenschist facies metamorphism under high fO₂ (Hematite-Magnetite buffer). Up to 15.34 mol% of jadeite component in aegirine suggests that the metamorphic grade of the nepheline syenite gneiss reached at least to greenschist-amphibolite transitional facies or higher. Nepheline geothermometry suggests temperature of metamorphism <500 °C, which is consistent with greenschist facies metamorphism of surrounding chlorite-biotite-garnet phyllite country rock.  相似文献   

A study of solar modulation of medium energy primary cosmic ray nuclei     

Projit K. Das  T. D. Goswami 《Journal of Astrophysics and Astronomy》1985,6(1):57-60

The energy spectra of primary cosmic rays were studied in the energy interval 150 to 450 MeV/nucl by using balloon-borne cellulose-nitrate solid-state plastic detector. Effects of solar modulation were studied using the theoretical spectrum ofH ₁ nuclei near the solar minimum in 1964 as the demodulated spectrum. The ‘force-field’ potential which fit the experimental results was estimated to be 270 MeV/nucl.  相似文献   

Abundance analysis of the long period southern cepheid RZ Vel     

Sunetra Giridhar  A. Arellano Ferro  Aruna Goswami 《Journal of Astrophysics and Astronomy》1991,12(1):27-37

The long period classical cepheid RZ Vel (HD 73502) is known to be a member of an OB association, Vel OB1 in Vela, and a high metallicity is ascribed to it by the photometric work of Eggen (1982). We have done an abundance analysis for this long period (P = 20.4 days) and hence young (age ≈ 1.80×10⁷ yr) classical cepheid using high resolution CCD spectra with good S/N ratio. We have used a detailed model atmosphere method to derive the abundances of the light elements C, O, A1, S and of many Fe-peak elements and a few s-process elements. Our present work indicates near solar abundance for most of the elements for RZ Vel and hence we do not confirm the high metallicity derived photometrically by Eggen (1982) for this star  相似文献