Understanding the turbulent structure of the atmospheric boundary layer: A diagnostic approach     

M Chatterjee  G K Sen  D K Sinha 《Journal of Earth System Science》1996,105(1):63-80

In this paper, we have attempted a diagnostic study of the turbulence characteristics of the ABL by means of two one-dimensional models. The first model uses a first order non-local closure, based on the Transilient Turbulence Theory, for parameterizing turbulent fluxes. while the second model uses second order local closure for parameterizing these. The models have been applied to conduct case studies using the Kytoon data taken at Kharagpur, during 17th–21st June, 1990, as part of the MONTBLEX programme. Our findings bring out various interesting features regarding the non-local and local turbulent statistics such as kinematic fluxes, turbulence kinetic energy, vertical velocity variance, the contribution of the eddies of various sizes to the fluxes at different level and the mixing lengths. The one-dimensional anisotropy of the turbulent eddies has been revealed by the findings from the transilient model. The vertical variation of the turbulence kinetic energy, as computed directly by the second order model, is found to be strongly correlated with the vertical velocity variance. In particular, for stably stratified boundary layers, identification of two distinct zones of the turbulence kinetic energy and corresponding vertical velocity maxima is possible, which has been interpreted as positive evidence of patchy turbulence in the boundary layer.  相似文献   

Physical and chemical response of zircons to deformation   总被引：1，自引：0，他引：1  

David M. Wayne  A. Krishna Sinha 《Contributions to Mineralogy and Petrology》1988,98(1):109-121

An investigation of U-Pb isotopic systematics in zircons from mylonitized Henderson Gneiss (Sinha and Glover 1978) revealed that selected zircon fractions from the mylonite zone suffered total loss of radiogenic Pb at 460 m.y. To further investigate the relationship between Pb loss, U gain, and grain size reduction associated with increasing strain in the shear zone, we have characterized the chemistry and morphology of zircons in the mylonitic rocks, using both electron microprobe analysis and scanning electron microscopy.SEM photographs of the zircons indicate that strain-correlated fracturing and size reduction of the zircons accompanied Pb loss throughout the mylonite zone. Stresses imposed by the expansion of initially U-rich, -damaged portions of the crystal resulted in microfracturing of the more brittle crystalline material proximal to the U-rich zones. During mylonitization, fractures propagated preferentially along these zones allowing metamorphic fluids to penetrate the easily-leached, -damaged portions of the zircons. Removal of 75% of the radiogenic Pb from zircons in the least-deformed zone of the mylonites may have occurred via this mechanism.Irregular, porous zircon overgrowths are also evident from the SEM photographs. Overgrowths are strongly enriched in U, Y and P with respect to the relict, Henderson Gneiss-derived cores, and tend to increase in volume from the protomylonite to the blastomylonite. Thus, the development of overgrowths on the zircons accounts for the U gain observed by Sinha and Glover (1978), and indicates that the transport of high field strength cations (e.g., Zr⁴⁺, Hf⁴⁺, U⁴⁺, etc.) occurred during prograde mylonitization at 460 m.y.A retrograde shearing event at 273 m.y. caused no further disturbance in the U-Pb isotopic systematics of the zircons. Pb retention by zircons during the later episode may have been the result of 1) the participation of H₂O-rich, relatively noncorrosive fluids and/or 2) the lack of further fracturing and size reduction in a strain gradient of lower magnitude than the prograde event.  相似文献   

The Influence of a Teleost Clarias batrachus (L.) on the Behaviour of Different Species of Nitrogen in Water     

B. B. Jana  S. Sengupta  M. Sinha 《洁净——土壤、空气、水》1986,14(4):375-384

Different experimental conditions (fed large, fed small, starved large, starved small groups, batch offered ration during experiment and low fish loading for a constant volume of water) of the carnivorous fish Clarias batrachus resulted in marked changes in the concentration of different N species (ammonium-N, nitrate-N, nitrate-N, organic-N as well as the sum of all forms of N) in aquaria water. Organic forms of nitrogen were the most important species of nitrogen excreted by the test fish. The maintenance nitrogen excretion rate was distinctly higher in larger fishes than in smaller ones. Different species of N were found to differ significantly depending upon the fed or starved conditions as well as small or large groups. A reduced level of oxygen in experimental aquaria inhibited the synthesis of nitrate which was maximum in control aquaria with considerably higher values of oxygen.  相似文献   

The numerical simulation of storm surges along the Bangladesh coast     

S. K. Dube  P. C. Sinha  G. D. Roy 《Dynamics of Atmospheres and Oceans》1985,9(2):121-133

Using a set of basic hydrodynamic equations governing the motion in a sea, a vertically-integrated coastal zone numerical model has been developed for the simulation of storm surges generated by the tropical stroms striking the Bangladesh coast. The model is fully nonlinear and uses a conditionally stable semi-explicit finite difference scheme for solving the relevant equations. In this model the analysis area extends from 87°E to 93°E along the south coast of Bangladesh and there are three open-sea boundaries situated along 87°E, 93°E and 19°N. With this analysis area it is possible to record, on average, 24 h of the surge generating capacity of most of the severe cyclones before landfall at the Bangladesh coast.Numerical experiments are performed with the help of this model to simulate the surges generated by several severe cyclonic storms which struck the Bangladesh coast durin the past 25 y. To compare the model predicted surges with the observed sea-surface elevations, three cyclonic storms have been chosen for which reliable observations regarding storm characteristics and the associated surges were available. The predicted peak sea-surface elevations compare well with the observed values at Chittagong port.  相似文献   

Strontium isotopic and selected trace element variations between two Aleutian volcanic centers (Adak and Atka): implications for the development of arc volcanic plumbing systems     

James D. Myers  Bruce D. Marsh  A. Krishna Sinha 《Contributions to Mineralogy and Petrology》1985,91(3):221-234

Major and trace element concentrations and initial ⁸⁷Sr/⁸⁶Sr ratios of lavas from the Aleutian volcanic centers of Adak and Atka have been used to study the evolution of their respective lithospheric plumbing systems. The centers are within 150 km of one another and show similar overall silica ranges (47–67%), but Adak (40 km³) is smaller than Atka (200 km³). Adak's lavas are chemically and isotopically heterogeneous (⁸⁷Sr/⁸⁶Sr:0.70285–0.70330) and two units contain lithospheric xenoliths. The lavas of the much larger Atka, on the other hand, have much less variability in major and trace elements as well as ⁸⁷Sr/⁸⁶Sr (0.70320–0.70345). We suggest that these characteristics are a measure of the relative maturity and cleanliness of the lithospheric plumbing systems that supply magma to these centers. Because Aleutian volcanic centers often remain fixed for relatively long periods of time (5 m.y.), once established, magmatic passageways are repeatedly used. Young plumbing systems are relatively cool and contain large amounts of wallrock contaminant, and ascending magmas undergo contamination as well as concurrent crystallization and fractionation. With time, however, heat and mass transfer between ascending magmas and wallrock produce thermal and chemical boundary layers that insulate subsequent magmas. In effect, the plumbing system matures. The chemical heterogeneity displayed by young, dirty systems (like Adak) reflects not only the magma source but also the wallrock encountered during ascent and possibly the effects of extensive crystal fractionation. Thus, it is the petrologic data of mature, clean systems, like Atka, that yield the most direct and unambiguous information on the ultimate origin of the lavas and their near surface evolution.  相似文献   

The Influence of the Fish Clarias batrachus on the Physicochemical Properties of Water under Laboratory Conditions     

B. B. Jana  M. Sinha  S. Gupta 《洁净——土壤、空气、水》1984,12(1):107-113

  相似文献   

Book reviews     

Carol Stoker  S. K. Sinha  David Pimentel 《Climatic change》1984,6(1):99-102

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Storm Surges from Extra-Tropical Cyclones   总被引：1，自引：0，他引：1  

Danard  M. B.  Dube  S. K.  Gönnert  G.  Munroe  Adam  Murty  T. S.  Chittibabu  P.  Rao  A. D.  Sinha  P. C. 《Natural Hazards》2004,32(2):177-190

The possible influence of climate change on the tracks of the extra-tropical cyclones as well as storm surges is studied. Two differentdata bases have been used: one for the Great Lakes of North America and the otherfor the German Bight in the North Sea of Europe. For the Great Lakes region,significant east-west and north-south shifts in the tracks of ETC'S with decadal periodicities have been observed. However, there was no trend in the amplitudes of storm surges. The most important result for the Great Lakes is that, depending upon its position relative to the constantly shifting storm tracks, a given location could eitherexperience a major storm surge or could miss out completely.The storm surges in the German Bight in general, and at Cuxhaven in particular, appear to show a slightly increasing trend in the latterpart of the 20th century. However, the most significant result for the German Bightis that the number of storm tides (i.e., multiple peaks in a given storm surge event)definitely has shown an increase in the second half of the 20th century. This increase isinterpreted as due to the influence of meso-scale weather systems embedded in the synoptic scale ETCs.  相似文献   

A Breadth Averaged Numerical Model for Suspended Sediment Transport in Hooghly Estuary,East Coast of India   总被引：2，自引：0，他引：2  

Sinha  P. C.  Guliani  Pragya  Jena  G. K.  Rao  A. D.  Dube  S. K.  Chatterjee  A. K.  Murty  Tad 《Natural Hazards》2004,32(2):239-255

Sedimentation is of vital concern in the conservation, development and utilization ofour soil and water resources. The suspended sediment in estuarine waters is hazardousto navigation in estuaries, which have important ports and harbours. A breadth-averagednumerical model to study circulation and sediment transport is presented in this paper.The model is applied to Hooghly estuary, along the east coast of India. The model is fullynon-linear and uses a semi-explicit finite difference scheme to solve mass, momentum andadvection diffusion equation for suspended sediments in a vertical plane. The erosion anddeposition have been computed by empirically developed source and sink terms in thesuspended sediment equation.  相似文献   

Determination of zircon/melt trace element partition coefficients from SIMS analysis of melt inclusions in zircon   总被引：3，自引：0，他引：3  

J.B Thomas  R.J BodnarN Shimizu  A.K Sinha 《Geochimica et cosmochimica acta》2002,66(16):2887-2901

Partition coefficients (^zircon/meltD_M) for rare earth elements (REE) (La, Ce, Nd, Sm, Dy, Er and Yb) and other trace elements (Ba, Rb, B, Sr, Ti, Y and Nb) between zircon and melt have been calculated from secondary ion mass spectrometric (SIMS) analyses of zircon/melt inclusion pairs. The melt inclusion-mineral (MIM) technique shows that D_REE increase in compatibility with increasing atomic number, similar to results of previous studies. However, D_REE determined using the MIM technique are, in general, lower than previously reported values. Calculated D_REE indicate that light REE with atomic numbers less than Sm are incompatible in zircon and become more incompatible with decreasing atomic number. This behavior is in contrast to most previously published results which indicate D > 1 and define a flat partitioning pattern for elements from La through Sm. The partition coefficients for the heavy REE determined using the MIM technique are lower than previously published results by factors of ≈15 to 20 but follow a similar trend. These differences are thought to reflect the effects of mineral and/or glass contaminants in samples from earlier studies which employed bulk analysis techniques.D_REE determined using the MIM technique agree well with values predicted using the equations of Brice (1975), which are based on the size and elasticity of crystallographic sites. The presence of Ce⁴⁺ in the melt results in elevated D_Ce compared to neighboring REE due to the similar valence and size of Ce⁴⁺ and Zr⁴⁺. Predicted ^zircon/meltD values for Ce⁴⁺ and Ce³⁺ indicate that the Ce⁴⁺/Ce³⁺ ratios of the melt ranged from about 10⁻³ to 10⁻². Partition coefficients for other trace elements determined in this study increase in compatibility in the order Ba < Rb < B < Sr < Ti < Y < Nb, with Ba, Rb, B and Sr showing incompatible behavior (D_M < 1.0), and Ti, Y and Nb showing compatible behavior (D_M > 1.0).The effect of partition coefficients on melt evolution during petrogenetic modeling was examined using partition coefficients determined in this study and compared to trends obtained using published partition coefficients. The lower D_REE determined in this study result in smaller REE bulk distribution coefficients, for a given mineral assemblage, compared to those calculated using previously reported values. As an example, fractional crystallization of an assemblage composed of 35% hornblende, 64.5% plagioclase and 0.5% zircon produces a melt that becomes increasingly more enriched in Yb using the D_Yb from this study. Using D_Yb from Fujimaki (1986) results in a melt that becomes progressively depleted in Yb during crystallization.  相似文献