Recent changes in the spatio-temporal characteristics of monsoon intraseasonal oscillations     

Joseph  Susmitha  Sahai  A. K.  Shabu  Hindhiya  Chattopadhyay  R.  Kaur  Manpreet 《Theoretical and Applied Climatology》2022,147(1-2):251-264

Theoretical and Applied Climatology - Monsoon intraseasonal oscillations (MISOs) define a significant proportion of intraseasonal variability of the Indian summer monsoon. In the backdrop of...  相似文献   

Alkaline intrusion in a granulite ensemble in the eastern ghats belt,India: Shear zone pathway and a pull-apart structure     

S.?BhattacharyaEmail author  Rajib?Kar 《Journal of Earth System Science》2004,113(1):37-48

The alkaline complex of Koraput, Orissa, India, is one of several bodies in the high-grade Eastern Ghats belt, but this one is an integral part of the high-grade belt and remote from the western boundary against the Bastar craton. The Koraput complex forms a lozenge-shaped intrusion into the metapelitic granulites and is bounded by shear zones. The combined effect of movement along these shear zones, is a northeasterly elongated sygmoidal cavity with maximum width along the northwesterly trending Reidel shear. Thus the Koraput alkaline complex can be considered to have been emplaced in a pull-apart structure, developed in the granulitic country rocks. Moreover, in view of the fact that the western margin of the high-grade Eastern Ghats belt bears clear evidence of collisional features, rather than that of rifting or break-up, the rift-valley model for the alkaline magmatism in this high-grade belt appears untenable.  相似文献   

Hydroclimatic modelling of local sea level rise and its projection in future     

A.?Naren  Rajib?MaityEmail author 《Theoretical and Applied Climatology》2017,127(3-4):761-767

Based on the National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalysis temperature dataset in the period of 1948–2014, the temperature contrast between the Arctic and equator in the pre- and post periods of the 1976/1977 regime shift is compared. An index measuring the temperature contrast is defined as the difference between the Arctic zone (70° N–90° N) and the equatorial region (10° S–10° N). The variations of the temperature contrast can be mainly explained by the local sea ice variations through sea ice–albedo–temperature feedback before 1976/1977 and the energy transportation to the Arctic together with the local sea ice after 1976/1977. The impacts of the Arctic minus equator (AmE) temperature contrast on the high-level westerly jet, and the polar easterlies show a significant difference during the two periods. A strong temperature anomaly associated with the temperature contrast in the two periods is found in the high latitude, but different patterns are observed at the high and low levels. The correlated water vapor appeared in the Indian Ocean and Maritime Continent before 1976/1977 and moved to northeastern Canada and eastern North America after 1976/1977.  相似文献   

The initiation and linkage of surface fractures above a buried strike-slip fault: An experimental approach   总被引：1，自引：0，他引：1  

N. Ghosh  A. Chattopadhyay 《Journal of Earth System Science》2008,117(1):23-32

Surface fractures in the overburdened sedimentary rocks, formed above a deep-seated basement fault, often provide important information about the kinematics of the underlying master fault. It has already been established that these surface fractures dynamically evolve and link one another with progressive displacement on the master fault below. In the present study, two different series of riedel-type experiments were carried out with clay analogue models under different boundary conditions viz., (i) heterogeneous simple shear of the cover rocks above a buried strike slip fault (wrench system) and (ii) heterogeneous simple shear with a component of shear-normal compression of the overburden package above a basement fault (transpressional system), to observe the initiation and linkage of surface fractures with varying T′ (where T′ = thickness of the overburden normalized with respect to the width of the master fault). In the wrench system, Riedel (R) shears were linked by principal displacement (Y) shears at early stages (shear strain of 0.8 to 1) in thin (2 < T′ < 18) models and finally (at a minimum shear strain of 1.4) gave rise to a through-going fault parallel to the basement fault without development of any other fracture. Conjugate Riedel (R′) shears develop only within the thicker (T′ > 18) clay models at a minimum shear strain of 0.7. With increasing deformation (at a minimum shear strain of 1.2) two R′ shears were joined by an R shear and finally opened up to make a sigmoidal vein with an asymmetry antithetic to the major fault-movement sense. Under transpression, the results were similar to that of heterogeneous simple shear for layers 2 < T′ < 15. In layers of intermediate thickness (15 < T′ < 25) early formed high angle R shears were cross cut by low angle R shears (at a minimum shear strain of 0.5 and shortening of 0.028) and “Riedel-within-Riedel” shears were formed within thick (T′ > 25) models (at minimum shear strain of 0.7 and shortening of 0.1), with marked angularity of secondary fault zone with the master fault at depth.  相似文献   

Application of criteria and indicators in community based sustainable mangrove management in the Sunderbans,India     

Debajit Datta  P. Guha  R.N. Chattopadhyay 《Ocean & Coastal Management》2010,53(8):468-477

Management of mangroves in a sustainable ecological as well as economic way is a difficult proposition and needs multi-disciplinary intervention. This paper highlights the importance of criteria and indicators to evaluate the status of performance of communities in managing their mangroves sustainably. The framework developed on the basis of 6 principles, 12 criteria, 36 indicators and 47 verifiers had been applied for assessment of Eco-Development Committees of the Sunderbans, India. Results show the presence of a highly positive correlation between performance of the committees and condition of the mangrove environment. Level of implementation of legal and institutional management strategies to protect mangroves proves to be the essential pre-condition in achieving sustainability. The study further demonstrates the effectiveness of the developed framework in the context of community forestry since the methodology was designed to be simple and flexible so as to apply it in forest management unit level without any major difficulty.  相似文献   

North Indian heavy rainfall event during June 2013: diagnostics and extended range prediction     

Susmitha Joseph  A. K. Sahai  S. Sharmila  S. Abhilash  N. Borah  R. Chattopadhyay  P. A. Pillai  M. Rajeevan  Arun Kumar 《Climate Dynamics》2015,44(7-8):2049-2065

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Generation of granitic plutons during Crustal orogenesis: An example from the Eastern Ghats granulite belt     

Rajib Kar 《Journal of the Geological Society of India》2012,80(5):653-666

Stock-like granite plutons in the Eastern Ghats belt and their host granulites exhibit similar solid state fabric. Both mineralogically and chemically these plutons are peraluminous and granitic in composition with S-type granite affinities. The granite plutons are product of a variety of mica dehydration melting reactions, as evident from their (1) compositional plots in the (FeO + MgO) ?? Na₂O.Al₂O₃ ?? K₂O.Al₂O₃ (MNK) pseudoternary diagram and (2) trace element contents. Muscovite and/or biotite breakdown reaction with or without plagioclase are the characteristic melting reactions. Restitic signature is evident in the host metapelitic granulites, locally known as khondalites (Qtz-Kfs-Grt-Sil-Fe-Ti oxides-bearing gneisses). The compositional variability of the associated khondalites can be a result of (1) original compositional variation and (2) they represent different stages of restites. Trace element monitoring following restite separation model suggests that these granite plutons are largely saturated equilibrium melts. The granites are chemically discriminated as syn-collisional. The plutons could also be the product of segregation during the regional exhumation of the Eastern Ghats terrain.  相似文献   

Assessment of the spatio-temporal distribution of soil properties in East Kolkata wetland ecosystem (A Ramsar site: 1208)     

S Pal  S Manna  A Aich  B Chattopadhyay  S K Mukhopadhyay 《Journal of Earth System Science》2014,123(4):729-740

The present investigation was made to characterize spatial and temporal variations in soil properties and to evaluate possible differences that could be dependent on the tannery effluent discharges, municipal sewage discharges, vegetation cover, soil settlement rate, crop rotation, etc. Soil total organic matter (TOM), cations like, Sodium (Na), Ammonium (NH₄), Potassium (K), Calcium (Ca) and Magnesium (Mg) contents in the bank soils and bottom sediments were recorded from seven different characteristic sites in East Kolkata wetland ecosystem, a Ramsar site (Ramsar site No. 1208). The profile maps were constructed by geostatistical methods to describe the spatial distribution as well as temporal variations of all the factors to identify the influences of composite wastewaters. The work was initiated to identify causes and consequences of the waste dumping in the concerned region for the past hundred years and thereby to suggest necessary precautionary measures to prevent further loss of soil quality.  相似文献   

Recording and analyzing geospatially accurate structural data through ‘digital mapping’ technique: A case study from the Canisp Shear Zone,NW Scotland     

A. Chattopadhyay  R. E. Holdsworth  K. J. W. McCaffrey  R. W. Wilson 《Journal of the Geological Society of India》2010,75(1):43-59

Spatial accuracy of structural data is an important factor for construction of a properly scaled model of crustal structures. Digital Geological Mapping methods can add the required spatial accuracy to the data, and also can improve the versatility of the geological/structural map in many ways, which are difficult to achieve through conventional mapping techniques. The present paper describes the methodology of digital mapping and discusses its applicability in structural analyses in the Canisp Shear Zone (CSZ) — a reactivated continental basement structure in the Precambrian Lewisian Gneiss complex of NW Scottish Highland. The CSZ is reinterpreted as a major dextral transpressional shear zone developed during Laxfordian deformation. It overprinted an earlier Inverian shear zone fabric, and was later reactivated and/or overprinted by brittle shearing of different phases and different scales. Spatial analyses within the ArcGISTM environment has helped bring out the geological relationships between different types of structural data in the shear zone, highlighting the partitioning of deformation into zones of high and low strain. A kinematic interpretation based on the geospatial data analysis, combined with conventional stereographic projection technique, is presented.  相似文献   

Structural evolution of a gneiss dome in the axial zone of the proterozoic South Delhi Fold Belt in central Rajasthan     

Dhruba Mukhopadhyay  Nandini Chattopadhyay  Tapas Bhattacharyya 《Journal of the Geological Society of India》2010,75(1):18-31

The structural geometry of the Anasagar gneiss dome in the axial zone of the South Delhi Fold Belt is controlled by polyphase folding. It is classified as a thrust-related gneiss dome and not as a metamorphic core complex. Four phases of deformation have affected both the gneiss and the enveloping supracrustal rocks. D₂ and D₃ deformations probably represent early and late stages of a progressive deformation episode in a simple shear regime combined with compression. The contact between the gneiss and the supracrustal rocks is a dislocation plane (thrust) with top-to-east sense of movement which is consistent with the vergence of the D₂ folds. The thrust had a ramp-and-flat geometry at depth. At the present level of exposure it is a footwall flat (that is, parallel to the gneissosity in the footwall), but it truncates the bedding of the hanging wall at some places and is parallel at others. The thrusting was probably broadly coeval with the D₂ folds and the thrust plane is locally folded by D₂. D₂ and D₃ folds have similar style and orientation as the first and second phases respectively of major folds in the Delhi Supergroup of the South Delhi Fold Belt and these are mutually correlatable. It is suggested that D1 may be Pre-Delhi in age. Available geochronological data indicate that the emplacement of the Anasagar gneiss predated the formation of volcanic rocks in the Delhi Supergroup and also predated the main crust forming event in the fold belt. The Anasagar gneiss and its enveloping supracrustal rocks are probably older than the Delhi Supergroup.  相似文献