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Nikhil Ghodichore R Vinnarasi C T Dhanya Somnath Baidya Roy 《Journal of Earth System Science》2018,127(8):115
Various reanalyses have been utilized in numerous climate related researches around the globe, however, there exists considerable biasedness in these products, especially in precipitation and temperature data. The ability of these reanalysis products to simulate the precipitation and temperature patterns is observed to be satisfactory at global scale, while it differs significantly at regional scale, especially over regions of high spatio-temporal heterogeneity such as India. Therefore, it is essential to evaluate the applicability and robustness of reanalyses in climate related research. The annual and seasonal variability in spatio-temporal patterns and trends of precipitation and temperature data, with respect to the IMD gridded data over 34 yrs, are evaluated for six global reanalyses namely, NCEP/NCAR Reanalysis (NCEP R1), NCEP-DOE AMIP-2 Reanalysis (NCEP R2), Climate Forecast System Reanalysis (CFSR), ECMWF Interim Reanalysis (ERA-Interim), Modern Era Retrospective Analysis for Research and Application Land only model (MERRA-Land) and JMA 55-year Reanalysis (JRA-55). The ability of the reanalyses was tested based on several factors such as statistical and categorical indices, spells and trends, for annual and seasonal daily values. Several regional and seasonal differences were observed, particularly over high rainfall regions such as Western Ghats and northeastern India. MERRA-Land is found to give the best results for precipitation over India, which is attributed to the updated forcing data using gauge-based precipitation observations. Similarly, ERA-Interim and JRA-55 exhibit better performance for temperature than other datasets. All reanalyses failed to correctly reproduce the trends in IMD data, for both precipitation and temperature. These observations will provide a better perception on the reliability and applicability of reanalyses for climate and hydrological studies over India. 相似文献
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Coda Q in the Kachchh Basin, Western India Using Aftershocks of the Bhuj Earthquake of January 26, 2001 总被引：1，自引：0，他引：1
S. C. Gupta Ashwani Kumar A. K. Shukla G. Suresh P. R. Baidya 《Pure and Applied Geophysics》2006,163(8):1583-1595
QC-estimates of Kachchh Basin in western India have been obtained in a high frequency range from 1.5 to 24.0 Hz using the aftershock
data of Bhuj earthquake of January 26, 2001 recorded within an epicentral distance of 80 km. The decay of coda waves of 30
sec window from 186 seismograms has been analysed in four lapse time windows, adopting the single backscattering model. The
study shows that Qc is a function of frequency and increases as frequency increases. The frequency dependent Qc relations obtained for four lapse-time windows are: Qc=82 f1.17 (20–50 sec), Qc=106 f1.11 (30–60 sec), Qc=126f1.03 (40–70 sec) and Qc=122f1.02 (50–80 sec). These empirical relations represent the average attenuation properties of a zone covering the surface area of
about 11,000, 20,000, 28,000 and 38,000 square km and a depth extent of about 60, 80, 95, 110 km, respectively. With increasing
window length, the degree of frequency dependence, n, decreases marginally from 1.17 to 1.02, whereas Q0 increases significantly from 82 to 122. At lower frequencies up to 6 Hz, Qc−1 of Kachchh Basin is in agreement with other regions of the world, whereas at higher frequencies from 12 to 24 Hz it is found
to be low. 相似文献
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Reliability analysis for bearing capacity of surface strip footing using fuzzy finite element method
Rajarshi Pramanik Dilip Kumar Baidya Nirjhar Dhang 《Geomechanics and Geoengineering》2020,15(1):29-41
ABSTRACTThis paper presents the reliability analysis on the basis of the foundation failure against bearing capacity using the concept of fuzzy set theory. A surface strip footing is considered for the analysis and the bearing capacity is estimated using the conventional Finite Element Method (FEM). The spatial variability of the variables is taken into consideration to capture the physical randomness of the soil parameters for an isotropic field. A variation of the probability of failure (Pf) against a varying limiting applied pressure (q) is presented for different Coefficient of Variation (COV) of the variables and different scale of fluctuation (θ). The results reveal that the friction angle of soil (?) is the most influencing parameter among the other variables. Further, the influence of the scale of fluctuation (θ) on the probability of failure (Pf) is also examined. It is observed that for a particular COV of ?, higher value of θ predicts higher Pf whereas, Pf increases as COV of ? increases for a particular θ value. Later, a comparison study is accomplished to verify the viability of the present method and it can be noticed that the present method compares well with the other reliability method (First Order Reliability Method) to a reasonably good extent. 相似文献
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The present experimental investigations study the effect of layering over rigid base on the dynamic behavior of foundation under vertical mode of vibration. Model block vibration tests were conducted on a rigid surface footing resting on different layered soil systems underlain by rigid base. The rigid base was used to simulate the presence of bedrock. The tests were carried out in a pit of size 2.0?m?×?2.0?m?×?1.9?m (deep) using a concrete footing of size 0.4?m?×?0.4?m?×?0.1?m. A rotating mass type mechanical oscillator was used for inducing vibration in vertical direction. Different layered soil systems were prepared within the total depth of 1,200?mm over the rigid base. Locally available gravel and fly ash were used to form different layered soil systems. In total, 132 nos. model block vibration tests in vertical mode were conducted for different layering and loading combinations. The experimentally obtained results are also compared with the results obtained from the analysis by mass-spring-dashpot and equivalent half-space theory. 相似文献
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Dynamic Response of Machine Foundation on Layered Soil: Cone Model Versus Experiments 总被引：1，自引：0，他引：1
P. K. Pradhan A. Mandal D. K. Baidya D. P. Ghosh 《Geotechnical and Geological Engineering》2008,26(4):453-468
This paper presents the experimental validation of analytical solution based on cone model for machine foundation vibration
analysis on layered soil. Impedance functions for a rigid massless circular foundation resting on a two layered soil system
subjected to vertical harmonic excitation are found using cone model. Linear hysteretic material damping is introduced using
correspondence principle. The frequency-amplitude response of a massive foundation is then computed using impedance functions.
To verify the solution field experiments are conducted in two different layered soil systems such as gravel layer over in situ
soil and gravel layer over concrete slab (rigid base). A total 72 numbers of vertical vibration tests on square model footing
were conducted using Lazan type mechanical oscillator, varying the influencing parameters such as depth of top layer, static
weight of foundation and dynamic force level. The frequency-amplitude response in general and in particular the resonant frequencies
and resonant amplitudes predicted by cone model is compared with the results of experimental investigation, which shows a
close agreement. Thus the cone model is reliable in its application to machine foundation vibration on layered soil. 相似文献
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Natural Hazards - The recurring flooding causes loss of life and damage to buildings and other structures, including bridges, sewerage systems, roadways and canals. It also frequently damages power... 相似文献
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Saurodeep Chatterjee Supriya Mondal Debesh Gain Tapan Kr Baidya Dipanjan Mazumdar 《Journal of Earth System Science》2018,127(6):89
The present work deals with the generations of Fe–Ti oxides and the variation in magnetic fabrics of the Dalma lavas and associated meta-sediments of the Singhbhum Mobile Belt (SMB) in relation to tectonics. Generations of the Fe–Ti oxides are different in meta-sediments and volcanics, the former preserving upliftment related oxidised grains, whereas the latter contains fresh grains prompting towards their upliftment due to plume upwelling before the volcanic eruption. In the meta-sediments, the magnetic fabric has close accordance with \(\hbox {D}_{2}/\hbox {F}_{2}\) event revealing synchronous development with \(\hbox {D}_{2}\). The Dalma thrust developed a sudden break in the homogeneity of the magnetic fabrics of the rocks where the magnetic foliations are all parallel to the Dalma thrust. This also causes \(P_{j}\) to be highest in this sector. The magnetic fabrics of volcanic rocks are different from the meta-sediments and record no signature of deformation. The pattern of distribution of susceptibility axes are in accordance with the subaerial lava flows. However, their \(\hbox {K}_{1}\) and \(\hbox {K}_{2}\) dispersed throughout the periphery with \(\hbox {K}_{3}\) clustering at the centre. This infers towards the fact that although the volcanism took place in a subaerial environment, calm aqueous environment was locally present where the oblate grains settled on the eruption surface with their \(\hbox {K}_{3}\) vertical. 相似文献
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S. K. Singh J. F. Pacheco M. Ordaz R. S. Dattatrayam G. Suresh P. R. Baidya 《Natural Hazards》2012,64(2):1491-1510
In this paper, we report that the ratio of broadband energy (0.01?C2?Hz) to high-frequency energy (0.3?C2?Hz), E r, estimated from regional seismograms of India, might be a useful parameter in estimating tsunami potential of earthquakes in the Sumatra?CAndaman region. E r is expected to be sensitive to the depth as well as to the source characteristics of an earthquake. Since a shallow and slow earthquake has a greater tsunamigenic potential, E r may be a useful diagnostic parameter. We base our analysis on broadband seismograms of the great earthquakes of Sumatra?CAndaman (2004, M w?~?9.2) and Nias (2005, M w 8.6), 41 of their aftershocks, and the earthquakes of north Sumatra (2010, M w 7.8) and Nicobar (2010, M w 7.4) recorded at VISK, a station located on the east coast of India. In the analysis, we also included the two recent, great strike-slip earthquakes of north Sumatra (2012, M w 8.6, 8.2) recorded at VISK and three south Sumatra earthquakes (2007, M w 8.5; 2007, M w 7.9; 2010, M w 7.8) recorded at PALK, a station in Sri Lanka. We find that E r is a function of depth; shallower earthquakes have higher E r values than the deeper ones. Thus, E r may be indicative of tsunamigenic potential of an earthquake. As M w and E r increase so does the tsunami potential. In addition to the parameter E r, the radiated seismic energy, E s, may be estimated from the regional seismograms in India using empirical Green??s function technique. The technique yields reliable E s for the great Sumatra and Nias earthquakes. E r and E s computed from VISK data, along with M w and focal mechanism, may be useful in estimating tsunami potential along the east coast of India from earthquakes in the Sumatra?CAndaman region in less than ~20?min. 相似文献
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Virupaxa K Banakar Sweta Baidya Alexander M Piotrowski D Shankar 《Journal of Earth System Science》2017,126(6):87
The deglacial transition from the last glacial maximum at \(\sim \)20 kiloyears before present (ka) to the Holocene (11.7 ka to Present) was interrupted by millennial-scale cold reversals, viz., Antarctic Cold Reversal (\(\sim \)14.5–12.8 ka) and Greenland Younger Dryas (\(\sim \)12.8–11.8 ka) which had different timings and extent of cooling in each hemisphere. The cause of this synchronously initiated, but different hemispheric cooling during these cold reversals (Antarctic Cold Reversal \(\sim \)3\(^{\circ }\hbox {C}\) and Younger Dryas \(\sim \)10\(^{\circ }\hbox {C}\)) is elusive because \(\hbox {CO}_{2}\), the fundamental forcing for deglaciation, and Atlantic meridional overturning circulation, the driver of antiphased bipolar climate response, both fail to explain this asymmetry. We use centennial-resolution records of the local surface water \(\delta ^{18}\hbox {O}\) of the Eastern Arabian Sea, which constitutes a proxy for the precipitation associated with the Indian Summer Monsoon, and other tropical precipitation records to deduce the role of tropical forcing in the polar cold reversals. We hypothesize a mechanism for tropical forcing, via the Indian Summer Monsoons, of the polar cold reversals by migration of the Inter-Tropical Convergence Zone and the associated cross-equatorial heat transport. 相似文献