The Convective-Atmospheric-Boundary-Layer Height and its dependence upon Meteorological Variables At a Tropical Coastal Station during Onshore and Offshore Flows     

Davis  Edwin V.  Rajeev  K.  Sambhu Namboodiri  K. V. 《Boundary-Layer Meteorology》2022,183(1):143-166

Boundary-Layer Meteorology - The height of the atmospheric boundary layer (ABL) plays a crucial role in the vertical transport of energy, moisture, and pollutants from the surface. We investigate...  相似文献   

Abundance and size variation of Globorotalia menardii in the Northeastern Indian Ocean during the late quaternary     

Swati Bhonsale  Rajeev Saraswat 《Journal of the Geological Society of India》2012,80(6):771-782

Variation in absolute abundance, size and coiling direction ratio of the planktic foraminifera Globorotalia menardii during the late Quaternary have been studied in three cores, collected along a north-south transect from the northeastern Indian Ocean. Increased abundance and larger size is observed during the warm interglacial period, whereas, smaller and fewer G. menardii specimens are noted during the cold glacial periods. A comparatively better match between absolute abundance, size and oxygen isotopic composition of foraminifera as compared to carbon isotopic composition at all the locations indicates that the abundance and size of G. menardii is more affected by seawater temperature and salinity as compared to productivity changes. The amplitude and frequency of temporal changes in the abundance and size of G. menardii vary from core-to-core, indicating the influence of site-specific physico-chemical conditions. In comparison to the abundance and size, the coiling direction of G. menardii does not show any systematic change in any of the cores. The majority of the specimens coil sinistrally. We conclude that the absolute abundance and variation in the average size of G. menardii can be used to infer past climatic changes. However, the variation in coiling direction of G. menardii appears to be unaffected by late Quaternary paleoclimatic variations in the north-eastern Indian Ocean.  相似文献   

Preliminary phase equilibria of the nepheline-diopside system under variable pressures (up to 28 kb) and temperatures     

Puniti Singh  Rajeev Chopra  Alok K Gupta 《Journal of Earth System Science》1990,99(1):49-55

The nepheline-diopside join defines the ultra-alkaline portion of the basalt tetrahedron and the bulk composition of nephelinitic rocks lie in this join. Schairer and others established that under atmospheric pressure, the join cuts through the primary phase volumes of olivine_ss, carnegieite_ss and nepheline_ss. Melilite coexists with nepheline_ss, olivine_ss and diopside_ss below 1160±10°C and olivine reacts out at low temperature. Experimental studies on seven compositions show the presence of a pseudoeutectic at Ne₇₀Di₃₀ and 1420°C, where diopside_ss, nepheline_ss and liquid are in equilibrium. Olivine and melilite do not appear in the system and the assemblage below 1225±20°C is diopside_ss+nepheline_ss.  相似文献   

Lateral Variation of the Vertical Stress in Underground Mine Stopes Filled with Granular Backfills   总被引：1，自引：0，他引：1  

P. Rajeev  P. R. Sumanasekera  N. Sivakugan 《Geotechnical and Geological Engineering》2016,34(2):481-492

Marston’s theory and its modifications are widely used to predict the average vertical stress variation with depth within mine stopes. However, this does not model the lateral variation in vertical stress at a particular depth. In this study, a mathematical expression to simulate the vertical stress variation is developed using the experimental shear stress data of granular backfill. The developed model is validated against average vertical stress measured in the experiment. Therefore, the developed model has the advantage of determining both the average vertical stress and its distribution respectively, at a particular depth and a cross sectional area of the mine stope.  相似文献   

Drift of icebergs in the grand banks     

P.S. Cheema  H.N. Ahuja 《Ocean Engineering》1978,5(2):95-103

Canada's eastern continental shelf has been the focal point of an extensive search for hydrocarbons in recent years. International petroleum companies have spent millions of dollars in explorations during this time. Off the Newfoundland and Labrador coasts, 42 wildcat wells have been drilled. One of the major hostile elements to the oil drilling rig operators in this region is the threat of drifting icebergs.  相似文献   

Erratum to: Use of remote sensing in characterization and management of Dhamni micro-watershed of Chandrapur District of Maharashtra     

Elvis A. Shukla  Jagdish Prasad  M.S.S. Nagaraju  Rajeev Srivastava  D.L. Kauraw 《Journal of the Indian Society of Remote Sensing》2009,37(2):334

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Modelling crop canopy and residue rainfall interception effects on soil hydrological components for semi‐arid agriculture     

Joseph A. Kozak  Lajpat R. Ahuja  Timothy R. Green  Liwang Ma 《水文研究》2007,21(2):229-241

Crop canopies and residues have been shown to intercept a significant amount of rainfall. However, rainfall or irrigation interception by crops and residues has often been overlooked in hydrologic modelling. Crop canopy interception is controlled by canopy density and rainfall intensity and duration. Crop residue interception is a function of crop residue type, residue density and cover, and rainfall intensity and duration. We account for these controlling factors and present a model for both interception components based on Merriam's approach. The modified Merriam model and the current modelling approaches were examined and compared with two field studies and one laboratory study. The Merriam model is shown to agree well with measurements and was implemented within the Agricultural Research Service's Root Zone Water Quality Model (RZWQM). Using this enhanced version of RZWQM, three simulation studies were performed to examine the quantitative effects of rainfall interception by corn and wheat canopies and residues on soil hydrological components. Study I consisted of 10 separate hypothetical growing seasons (1991–2000) for canopy effects and 10 separate non‐growing seasons (1991–2000) for residue effects for eastern Colorado conditions. For actual management practices in a no‐till wheat–corn–fallow cropping sequence at Akron, Colorado (study II), a continuous 10‐year RZWQM simulation was performed to examine the cumulative changes on water balance components and crop growth caused by canopy and residue rainfall interception. Finally, to examine a higher precipitation environment, a hypothetical, no‐till wheat–corn–fallow rotation scenario at Corvallis, Oregon, was simulated (study III). For all studies, interception was shown to decrease infiltration, runoff, evapotranspiration from soil, deep seepage of water and chemical transport, macropore flow, leaf area index, and crop/grain yield. Because interception decreased both infiltration and soil evapotranspiration, no significant change in soil water storage was simulated. Nonetheless, these findings and the new interception models are significant new contributions for hydrologists. Published in 2006 John Wiley & Sons, Ltd.  相似文献   

Pressure-induced phase transition in Mg0.8Fe0.2O ferropericlase     

Innokenty Kantor  Leonid Dubrovinsky  Catherine McCammon  Anastasia Kantor  Sakura Pascarelli  Giuliana Aquilanti  Wilson Crichton  Maurizio Mattesini  Rajeev Ahuja  Jailton Almeida  Vadim Urusov 《Physics and Chemistry of Minerals》2006,33(1):35-44

Combined X-ray powder diffraction, Mössbauer, and XANES spectroscopy in situ experiments revealed the transformation of cubic (Mg_0.8Fe_0.2)O ferropericlase to a rhombohedrally distorted phase at 35(1) GPa and room temperature. The Mössbauer spectroscopy results show that the rhombohedral distortion does not involve magnetic ordering. Combined with data from the literature, our results imply that the cubic to rhombodedral transition occurs in (Mg,Fe)O under conditions of non-hydrostatic stress over a wide range of composition (0.2≤x _Fe≤1).  相似文献   

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   

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