Trend in Observed and Projected Maximum and Minimum Temperature over N-W Himalayan Basin     

Dharmaveer SINGH  Sanjay K JAIN  Rajan Dev GUPTA 《山地科学学报》2015,(2):417-433

Recently, study in past trends of climate variables gained significant consideration because of its contribution in adaptions and mitigation strategies for potential future changes in climate, primarily in the area of water resource management. Future interannual and inter-seasonal variations in maximum and minimum temperature may bring significant changes in hydrological systems and affect regional water resources. The present study has been performed to observe past(1970-2010) as well as future(2011-2100)spatial and temporal variability in temperature(maximum and minimum) over selected stations of Sutlej basin located in North-Western Himalayan region in India. The generation of future time series of temperature data at different stations is done using statistical downscaling technique. The nonparametric test methods, modified Mann-Kendall test and Cumulative Sum chart are used for detecting monotonic trend and sequential shift in time series of maximum and minimum temperature. Sen’s slope estimator test is used to detect the magnitude of change over a period of time on annual and seasonal basis. The cooling experienced in annual TMax and TMin at Kasol in past(1970-2010) would be replaced by warming in future as increasing trends are detected in TMax during 2020 s and 2050 s and in TMin during 2020 s, 2050 s and 2080 s under A1 B and A2 scenarios. Similar results of warming are also predicted at Sunnifor annual TMin in future under both scenarios which witnessed cooling during 1970-2010. The rise in TMin at Rampur is predicted to be continued in future as increasing trends are obtained under both the scenarios. Seasonal trend analysis reveals large variability in trends of TMax and TMin over these stations for the future periods.  相似文献   

Constraints on the Mantle Sources of the Deccan Traps from the Petrology and Geochemistry of the Basalts of Gujarat State (Western India)   总被引：6，自引：3，他引：3  

MELLUSO  L.; BECCALUVA  L.; BROTZU  P.; GREGNANIN  A.; GUPTA  A. K.; MORBIDELLI  L.; TRAVERSA  G. 《Journal of Petrology》1995,36(5):1393-1432

The late Cretaceous-early Tertiary flood basalts in the Gujaratarea of the northwestern Deccan Traps (Kathiawar peninsula,Pavagadh hills and Rajpipla) exhibit a wide range of compositions,from picrite basalts to rhyolites; moreover, the basaltic rockshave clearly distinct TiO₂ contents at any given degree of differentiationand strongly resemble the low-titanium and hightitanium basaltsfound in most of the Gondwana continental flood basalt (CFB)suites. Four magma groups are petrologically and geochemicallydistinguished: (1) A low-Ti group, characterized by rocks with varying SiO²saturation, and with TiO₂ <1•8 wt%, extremely low incompatibletrace element abundances, low Zr/ (av- 3•8), Ti/ V (av.27), and a very slight large ion lithophile element (LJLE) enrichmentover high field strength elements (HFSE). These rocks sharesome features with the Bushe Formation of the Western Ghatsfarther south, but have distinct geochemical characters, inparticular the strong depletion in most incompatible trace elements. (2) A high-Ti group, characterized by a more K-rich characterthan the low-Ti rocks, and with a strong enrichment in incompatibleelements, similar to average ocean island basalt (OIB), e.g.high TiO₂ (>1•8 wt% in picrites), Nb (>19 p.p.m.)Zr/ (av. 6•5) and Tt/V (av. 47). (3) An intermediate-Ti group, with TiO₂ contents slightly lowerthan the high-Ti rocks at the same degree of evolution, andwith correspondingly lower incompatible trace element contentsand ratios, in particular K₂O, Nb, Ba and Zr/Y (av. 5•2). (4) A potassium-rich group (KT), broadly similar in geochemicalcharacter to the high-Ti group but showing more extreme K, Rband Ba enrichment (av. K₂0/Na₂0l; Ba/Y20). The most primitive low-Ti and high-Ti picrites, when correctedfor low-pressure olivine fractionation, show distinct major(and trace) element geochemistry, in particular for CaO/AI₂O₃,CaO/TiO₂ and Al₂O₃/TiO₂, and moderate but significant variationsin their SiO₂ and Fe₂O_st contents; these characteristics stronglysuggest the involvement of different mantle sources, more depletedfor the low-Ti picrites, and richer in cpxfor the high-Ti picrites,but with broadly the same pressures of equilibration (27–14kbar). This, in turn, suggests a strong lateral heterogeneityin the Gujarat Trap mantle. Low-Ti picrites and related differentiatesin Kathiawar are reported systematically for the first timehere, and suggest the existence of HFSE-depleted mantle in thenorthwestern Deccan Traps, with extension at least to the SeychellesIslands and to the area of the Bushe Formation near Bombay inthe pre-drift position, before the development of the CarlsbergRidge. The absence of correlations between LILE/HFSE ratiosand SiO₂ argues against crustal contamination processes actingon the low-Ti picrites, possibly owing to their probably rapiduprise to the surface. Consequently, the mantle region of thisrock group was probably re-enriched by small amounts of ULE-richmaterials. The substantially higher, trace element enrichmentof the least differentiated high-Ti picrites, relative to thebasalts of the Ambe-noli and Mahableshwar Formations of theWestern Ghats, testifies also to the presence of more incompatibleelement rich, OIB4ike mantle sources in northern and northwesternGujarat. These sources were geochemicaily similar to the present-dayReunion mantle sources. KEY WORDS: Deccan Traps; geochemistry; petrology; picrite basalts; western India ^*Corresponding author, e-mail: mellujo{at}ds.cued.unina.it  相似文献   

Holocene Floral and Faunal Remains Revealed Concealed Neotectonic Disturbance (Saria Tal, Kumaun Himalaya, India)   总被引：1，自引：1，他引：0  

Asha GUPTA 《《地质学报》英文版》2010,84(1):69-76

Palynological and paleontological investigations supported by the radiocarbon dates of the lacustrine sediments of two profiles from the temperate lake Saria Tal, in Naini Tal District, Kumaun Himalaya, have revealed the presence of a concealed fold at the region. The profile from bore cores represents the upper part of the Late Holocene and the profile from exposed sections from the Middle Holocene to the over middle part of the Late Holocene. The data generated from different investigations have uniformly indicated that the former profile represents normal superposition, while the latter represents the reverse order. The contemporary pollen as well as molluscan zones of both profiles are situated at different elevations but consist of similar bioremains – indicating continuation of the same strata in two profiles. The presence of reverse order of superposition, continuation of the same strata in two profiles at different elevations, and the orientation of biozones, have indicated that the revealed folding is of syncline type. The present study has also given an idea about the origin of this lake.  相似文献   

Efficient two-dimensional magnetotellurics modelling using implicitly restarted Lanczos method     

KRISHNA KUMAR  PRAVIN K GUPTA  SRI NIWAS 《Journal of Earth System Science》2011,120(4):595-604

This paper presents an efficient algorithm, FDA2DMT (Free Decay Analysis for 2D Magnetotellurics (MT)), based on eigenmode approach to solve the relevant partial differential equation, for forward computation of two-dimensional (2D) responses. The main advantage of this approach lies in the fact that only a small subset of eigenvalues and corresponding eigenvectors are required for satisfactory results. This small subset (pre-specified number) of eigenmodes are obtained using shift and invert implementation of Implicitly Restarted Lanczos Method (IRLM). It has been established by experimentation that only 15–20% smallest eigenvalue and corresponding eigenvectors are sufficient to secure the acceptable accuracy. Once the single frequency response is computed using eigenmode approach, the responses for subsequent frequencies can be obtained in negligible time. Experiment design results for validation of FDA2DMT are presented by considering two synthetic models from COMMEMI report, Brewitt-Taylor and Weaver (1976) model and a field data based model from Garhwal Himalaya.  相似文献   

Improvements in medium range weather forecasting system of India     

V S PRASAD  SAJI MOHANDAS  SURYA KANTI DUTTA  M DAS GUPTA  G R IYENGAR  E N RAJAGOPAL  SWATI BASU 《Journal of Earth System Science》2014,123(2):247-258

Medium range weather forecasts are being generated in real time using Global Data Assimilation Forecasting System (GDAFS) at NCMRWF since 1994. The system has been continuously upgraded in terms of data usage, assimilation and forecasting system. Recently this system was upgraded to a horizontal resolution of T574 (about 22 km) with 64 levels in vertical. The assimilation scheme of this upgraded system is based on the latest Grid Statistical Interpolation (GSI) scheme and it has the provision to use most of available meteorological and oceanographic satellite datasets besides conventional meteorological observations. The new system has an improved procedure for relocating tropical cyclone to its observed position with the correct intensity. All these modifications have resulted in improvement of skill of medium range forecasts by about 1 day.  相似文献   

Two layers of Australasian impact ejecta in the Indian Ocean?     

M. Shyam PRASAD  S. M. GUPTA  V. N. KODAGALI 《Meteoritics & planetary science》2003,38(9):1373-1381

Abstract— Only 2 Australasian tektites have been found in the Indian Ocean, and both are associated with surficial sediments. We collected cores from both locations where the tektites have been reported. The microtektites in these cores (and both the tektites, as reported earlier) have chemical compositions within the compositional range previously reported for Australasian tektites and microtektites. In both locations, while the tektites are occurring at the sediment/water interface, the microtektites are found buried in older horizons beneath the seafloor at stratigraphic levels, conforming to the radiometric age of the strewn field. Thus, at first glance, there appear to be 2 layers of Australasian impact ejecta in the Indian Ocean. However, the manganese nodules are associated with the tektites which, although millions of years old, are invariably resting on recent sediments. Therefore, the mechanism that retains nodules at the seafloor also seems to be operative on the tektites, thus leading to this apparent “age paradox” of tektite/microtektite distribution in the Indian Ocean, although they both belong to the same impact event.  相似文献   

Influence of rigid boundary on the propagation of torsional surface wave in an inhomogeneous layer     

GUPTA  SHISHIR  SULTANA  REHENA  KUNDU  SANTIMOY 《Journal of Earth System Science》2015,124(1):161-170

Journal of Earth System Science - The present work illustrates a theoretical study on the effect of rigid boundary for the propagation of torsional surface wave in an inhomogeneous crustal layer...  相似文献   

Use of radon for evaluation of atmospheric transport models: sensitivity to emissions     

MOHAN L. GUPTA  ANNE R. DOUGLASS  S. RANDOLPH KAWA  STEVEN PAWSON 《Tellus. Series B, Chemical and physical meteorology》2004,56(5):404-412

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AIRS observations of seasonal variability in meridional temperature gradient over Indian region at 100 hPa     

A GUPTA  S K DHAKA  V PANWAR  R BHATNAGAR  V KUMAR  SAVITA M DATTA  S K DASH 《Journal of Earth System Science》2013,122(1):201-213

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Soil gas radon–thoron monitoring in Dharamsala area of north-west Himalayas, India using solid state nuclear track detectors     

GULSHAN KUMAR  ARVIND KUMAR  VIVEK WALIA  JITENDER KUMAR  VIKASH GUPTA  TSANYAO FRANK YANG  SURINDER SINGH  BIKRAMJIT SINGH BAJWA 《Journal of Earth System Science》2013,122(5):1295-1301

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