Recession of samudra tapu glacier, chandra river basin, Himachal Pradesh     

Anil V. Kulkarni  Sunil Dhar  B. P. Rathore  Babu Govindha Raj K.  Rajeev Kalia 《Journal of the Indian Society of Remote Sensing》2006,34(1):39-46

Himalayas possess one of the largest resources of snow, ice and glaciers that act as a huge freshwater reservoir. Monitoring the glaciers is important to assess the overall reservoir health of the Himalayas. Samudra Tapu is one of the largest glaciers in Chandra basin of district Lahaul and Spiti, Himachal Pradesh. Based on the field investigations and the remote sensing techniques. features such as accumulation area, ablation area snowline/equilibrium line, moraine-dammed lakes and permanent snowfields were mapped. The glacial terminus was identified using moraine-dammed lake, as lake is located at down streamside of the terminus. The total recession of glacier during the period of 38 years (1962–2000) is about 742 m with an average rate of 19.5 m/yr. In addition, glacial extent is reduced from 73 to 65 km² between 1962 and 2000. suggesting overall deglaciation of 11%. During field investigation. three stages of glaciation using terminal moraine were identified. These moraines were mapped by merging LISS-II1 and PAN data. At the peak of glaciation. the glacial terminus was extended 3.18 km downstream of terminus position in year 2000. Total area during peak of glaciation period has been observed to be 77.67 km², which is 12.67 km² higher than the present glacier extent.  相似文献   

Paleo-uplift and cooling rates from various orogenic belts of India, as revealed by radiometric ages—reply (2)     

Kewal K. Sharma  K.D. Bal  Rajinder Prashad  Lal Nand  K.K. Nagpaul 《Tectonophysics》1984,107(1-2)

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Extra-terrestrial influx rates of cosmogenic isotopes and platinum group elements: realizable geochemical effects     

Devendra Lal 《Geochimica et cosmochimica acta》2003,67(24):4925-4933

We present estimates of “realizable” influx of selected cosmogenic isotopes, ³He, ¹⁰Be, ²⁶Al, and ¹⁴C, and platinum group elements, Ir, Os, and Re on the earth via influx of meteoroids. We define realizable as the particulate fraction of mass influx which is included in standard geochemical analyses of terrestrial sediments. This is the surviving mass fraction of size < 0.5-1 cm, which gets mixed with terrestrial samples, and is analyzed in normal terrestrial assays of sediments. Larger surviving meteoroid fragments, of the order of cm to m or larger, obviously belong to the non-realizable flux category, since (i) their distribution in terrestrial samples would be very patchy, resulting in a highly variable density matrix, and (ii) they would also generally (except in wide-diameter cores) be excluded from sediment cores. We estimate the realizable influx of meteoritic particles, based on a recent model describing production of smaller size fragments arising during the atmospheric entry of meteoroids. Implicit in this work is the assumption that the secondary fragments are not subject to much heating and therefore most of the initial ³He (and noble gases) would be preserved in the secondary fragments since after break-up they are not subjected to much heating. Under this assumption, production of small size fragments in the ablation process constitutes a “safe” landing mechanism for parts of the meteoroid. In this paper, we show that the meteoritic ablation/fragmentation process produces a significant flux of ³He, platinum group metals, and cosmogenic ²⁶Al. In fact, measurements of these isotopes in ocean sediments should allow a reasonable estimate of temporal variations in the flux of meteoroids of 50 cm to 5 m radii, which produce most of the secondary fragments in the size range <1 cm.We would like to state here that, as pointed out in our previous work, stratospheric collections would be biased towards collection of the primary incident extra-terrestrial particles, whereas terrestrial accumulations representing large (area × time) accumulations, as in the case of ocean sediments, would efficiently sample the fragmented particles.  相似文献   

Modeling of the strong ground motion of 25th April 2015 Nepal earthquake using modified semi-empirical technique     

Sohan Lal  A. Joshi  Sandeep  Monu Tomer  Parveen Kumar  Chun-Hsiang Kuo  Che-Min Lin  Kuo-Liang Wen  M. L. Sharma 《Acta Geophysica》2018,66(4):461-477

On 25th April, 2015 a hazardous earthquake of moment magnitude 7.9 occurred in Nepal. Accelerographs were used to record the Nepal earthquake which is installed in the Kumaon region in the Himalayan state of Uttrakhand. The distance of the recorded stations in the Kumaon region from the epicenter of the earthquake is about 420–515 km. Modified semi-empirical technique of modeling finite faults has been used in this paper to simulate strong earthquake at these stations. Source parameters of the Nepal aftershock have been also calculated using the Brune model in the present study which are used in the modeling of the Nepal main shock. The obtained value of the seismic moment and stress drop is 8.26 × 10²⁵ dyn cm and 10.48 bar, respectively, for the aftershock from the Brune model .The simulated earthquake time series were compared with the observed records of the earthquake. The comparison of full waveform and its response spectra has been made to finalize the rupture parameters and its location. The rupture of the earthquake was propagated in the NE–SW direction from the hypocenter with the rupture velocity 3.0 km/s from a distance of 80 km from Kathmandu in NW direction at a depth of 12 km as per compared results.  相似文献   

Oxygen isotope records of Globigerina bulloides across a north-south transect in the south-western Indian Ocean     

Neloy Khare  Subodh Kumar Chaturvedi  Rajeev Saraswat 《Ocean Science Journal》2009,44(2):117-123

Along a north-south transect (9.69°N to 55.01°S) in the southwestern Indian Ocean during the Indian Pilot Expedition to Southern Ocean (PESO), the oxygen isotopic analysis of planktic foraminifera (Globigerina bulloides) from 23 surface sediment samples was carried out to assess the relationship between isotopic composition of G. bulloides and the prevailing physical (seawater temperature and salinity) conditions of the ambient seawater. An increasing trend in the δ¹⁸O value is noticed towards higher latitude. Apparently such an increase in δ¹⁸O values is inversely related to the temperature changes along the transect. However, slight mismatch is observed at a few stations due to calcification out of optimum conditions or due to the salinity changes. The preliminary results of the present study, if extended to the subsurface sediments coupled with other parameters, may contribute to the reconstruction of the paleohydrography of the region, especially the position of various seawater fronts during the geologic past albeit with areal limitation.  相似文献   

Species diversity and population status of threatened plants in different landscape elements of the Rohtang Pass,western Himalaya     

K. N. Singh  Gopichand  Amit Kumar  Brij Lal  N. P. Todaria 《山地科学学报》2008,5(1):73-83

This paper highlights the quantitative estimates of plant species diversity and ecosystems of the Rohtang Pass,which is one of the most preferred visiting spots by tourists in Himachal Pradesh （H.P.）,India. In spite of high pressure of anthropogenic activities,the Rohtang Pass still harbours a variety of flowering plants with economic value,including various medicinal herbs. In order to observe species diversity in different landscape elements （LSEs）,ground surveys were conducted in nine unique LSEs within the elevation range between 3624 m and 4332 m. Plant community structure in each LSE was studied using stratified random sampling where a total 56 quadrats of 1 m^2 in size for herbs and 7 quadrats of 25 m^2 for shrubs were made. Of the total 50 plant species belonging to 15 families recorded in different random quadrats,24 species were found of medicinal value. Maximum species richness （18） and value of Shannon diversity （H＇=2.2648） were observed on northeast-facing slope in Picrorhiza kurrooa dominated LSE in moist area,followed by Rheum emodi LSE （species richness = 17 and H＇ = 2.4141） distributed on south-facing slope. Maximum values of species richness and Shannon diversity in Rheum emodi LSE were observed between 8 ～ 12 and 1.4797 ～ 2.1911,respectively. Rhododendron anthopogon dominated LSE on northwest-facing slope was found least diverse in terms of species richness where the Simpson index of dominance （D） was 0.4205. The species were equal in abundance in P. kurrooa LSE on east-facing slope and Pleurospermum candollii LSE on north-facing slope,showing the maximum similarity in terms of species distribution between the two LSEs. Low turnover of species across common LSEs gives an idea regarding their limited distribution. Five species of threatened category according to the IUCN criteria were observed in seven LSEs. The largest population of threatened medicinal plants was recorded on northeast and northwest-facing slopes where population density of Bergenia stracheyi （  相似文献   

Climatic forcing before,during, and after the 8.2 Kyr B.P. global cooling event     

Devendra Lal  William G. Large  Stephan G. Walker 《Journal of Earth System Science》2007,116(3):171-177

This paper attempts at full characterization of the unique global 8.2 Kyr B.P. cooling event. Significant atmospheric cooling started during 9.5–8.5 Kyr B.P. when the Sun was extremely quiet during three periods of ∼ 50–100 years. The flood of melt water in the N. Atlantic from glacial lakes during the demise of the Laurentide ice sheet, starting at ∼ 8.5 Kyr B.P., adds to the atmospheric cooling. Climatic forcing events occurred at 8.5 Kyr B.P., at 8.2 Kyr B.P. and finally at 8.06 Kyr B.P., leading to concurrent increases or decreases in the atmospheric Δ¹⁴C levels, completely consistent with the climatic forcing proposed here.  相似文献   

New statistical models for long-range forecasting of southwest monsoon rainfall over India   总被引：2，自引：0，他引：2  

M. Rajeevan  D. S. Pai  R. Anil Kumar  B. Lal 《Climate Dynamics》2007,28(7-8):813-828

The India Meteorological Department (IMD) has been issuing long-range forecasts (LRF) based on statistical methods for the southwest monsoon rainfall over India (ISMR) for more than 100 years. Many statistical and dynamical models including the operational models of IMD failed to predict the recent deficient monsoon years of 2002 and 2004. In this paper, we report the improved results of new experimental statistical models developed for LRF of southwest monsoon seasonal (June–September) rainfall. These models were developed to facilitate the IMD’s present two-stage operational forecast strategy. Models based on the ensemble multiple linear regression (EMR) and projection pursuit regression (PPR) techniques were developed to forecast the ISMR. These models used new methods of predictor selection and model development. After carrying out a detailed analysis of various global climate data sets; two predictor sets, each consisting of six predictors were selected. Our model performance was evaluated for the period from 1981 to 2004 by sliding the model training period with a window length of 23 years. The new models showed better performance in their hindcast, compared to the model based on climatology. The Heidke scores for the three category forecasts during the verification period by the first stage models based on EMR and PPR methods were 0.5 and 0.44, respectively, and those of June models were 0.63 and 0.38, respectively. Root mean square error of these models during the verification period (1981–2004) varied between 4.56 and 6.75% from long period average (LPA) as against 10.0% from the LPA of the model based on climatology alone. These models were able to provide correct forecasts of the recent two deficient monsoon rainfall events (2002 and 2004). The experimental forecasts for the 2005 southwest monsoon season based on these models were also found to be accurate.  相似文献   

黄土高原黄土和红粘土~(10)Be地球化学特征   总被引：4，自引：0，他引：4       下载免费PDF全文

顾兆炎  D.Lal  郭正堂  J.Southon  M.W.Caffee  刘东生 《第四纪研究》2000,20(5)

充分认识元素和同位素在不同环境条件下的地球化学行为,是运用元素和同位素示踪环境变化的前提。对来自于黄土高原的黄土、古土壤和红粘土样品的宇宙成因核素10Be测量和化学成分分析,以及各种化学淋溶实验表明：10Be主要以吸附状态赋存于粉尘沉积物粘粒矿物的表面,部分已结合进自生的粘土矿物中;在粉尘沉积物风化过程中10BC与9Be和Al的活动性相似,基本没有发生迁移,其原因是连续沉积的粉尘含有大量的碱性物质,阻止了10Be的解吸附和淋滤;沉积和风化作用导致了10Be浓度与化学指标在黄土－古土壤和红粘土剖面中的协同变化。  相似文献   

Development of hyperspectral model for rapid monitoring of soil organic carbon under precision farming in the Indo-Gangetic Plains of Punjab,India     

Rajeev Srivastava  Dipak Sarkar  Siddhartha S. Mukhopadhayay  Anil Sood  Manjeet Singh  Ravindra A. Nasre  Sanjay A. Dhale 《Journal of the Indian Society of Remote Sensing》2015,43(4):751-759

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