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61.
Snow is a highly reflecting object found naturally on the Earth and its albedo is highly influenced by the amount and type
of contamination. In the present study, two major types of contaminants (soil and coal) have been used to understand their
effects on snow reflectance in the Himalayan region. These contaminants were used in two categories quantitatively – addition
in large quantity and addition in small quantity. Snow reflectance data were collected between 350 and 2500 nm spectral ranges
and binned at 10 nm interval by averaging. The experiment was designed to gather the field information in controlled conditions,
and radiometric observations were collected. First derivative, band absorption depth, asymmetry, percentage change in reflectance
and albedo in optical region were selected to identify and discriminate the type of contamination. Band absorption depth has
shown a subtle increasing pattern for soil contamination, however, it was significant for small amounts of coal contamination.
The absorption peak asymmetry was not significant for soil contamination but showed a nature towards left asymmetry for coal.
The width of absorption feature at 1025 nm was not significant for both the contaminations. The percentage change in reflectance
was quite high for small amount of coal contamination rather than soil contamination, however, a shift of peak was observed
in soil-contaminated snow which was not present in coal contamination. The albedo drops exponentially for coal contamination
rather than soil contamination. 相似文献
62.
A set of large deformation experiments are presented to simulate folding pattern at various energy states during formation.
In order to numerically simulate this phenomenon, a rectangular layer of shale is generated and compressed at various strain
rates. The results reveal the variation in distribution of stress along the length of the bed. The stress distribution during
elastic behaviour of shale bed at low compression rate and the change in stress distribution leading to rupture at high compression
rates is discussed. Wavelength, limb length, bulk shortening, stress distribution, displacement of particles along the length
of the bed is considered for comparative study of the fold pattern generated at various compression rates. The nature and
position of crack generated during the formation of fold is also explained. After rupture in shale bed, the generation of
fault and stress distribution in limbs of fold sliding over one another is also described. 相似文献
63.
V. S. SINGH 《水文科学杂志》2013,58(4):589-594
Abstract Well storage effect is generally considered while interpreting pumping test data from large diameter wells. However, in an aquifer of low permeability, the well storage is found to be significant during pumping tests conducted on bore wells. The interpretation of such data gives ambiguous results unless well storage effect is taken into account. A field example is presented to illustrate the difficulty in interpretation of the pumping test data. In order to take into account the well storage effect, a finite difference approach of interpreting pumping test data is suggested. 相似文献
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Abstract Streamflow in the Himalayan rivers is generated from rainfall, snow and ice. The distribution of runoff produced from these sources is such that the streamflow may be observed in these rivers throughout the year, i.e. they are perennial in nature. Snow and glacier melt runoff contributes substantially to the annual flows of these rivers and its estimation is required for the planning, development and management of the water resources of this region. The average contribution of snow and glacier melt runoff in the annual flows of the Satluj River at Bhakra Dam has been determined. Keeping in view the availability of data for the study basin, a water balance approach was used and a water budget period of 10 years (October 1986-September 1996) was considered for the analysis. The rainfall input to the study basin over the water budget period was computed from isohyets using rainfall data of 10 stations located at different elevations in the basin. The total volume of flow for the same period was computed using observed flow data of the Satluj River at Bhakra Dam. A relationship between temperature and evaporation was developed and used to estimate the evapotranspiration losses. The snow-covered area, and its depletion with time, was determined using satellite data. It was found that the average contribution of snow and glacier runoff in the annual flow of the Satluj River at Bhakra Dam is about 59%, the remaining 41% being from rain. 相似文献
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L. YILMAZ Vijay P. SINGH S.K. MISHRA D. D. ADRIAN J. J. SANSALONE Civil Engineering Faculty Hydraulic Division Technical University of Istanbul Maslak Istanbul Turkey 《国际泥沙研究》2002,17(1)
1 INTRODUCTION River erosion is a complex phenomenon. The rate of bank retreat is determined by flow, bed topography, sediment transport, bank properties, and water quality. Prediction of future river planform changes and the knowledge of river erosion and river meandering are required for land use planning in alluvial river valleys and determining locations for bridges and hydraulic structures. The control of riverbank erosion requires prediction of flow and bed features in a meanderin… 相似文献
69.
Thermal perturbation during charnockitization and granulite facies metamorphism in southern India 总被引：1，自引：0，他引：1
Abstract We have deduced the steady-state lithospheric geotherm at c. 1 Ga in the south Indian shield area using the available data on the concentration of radioactive elements, and the P-T conditions of Proterozoic mantle xenoliths in the south Indian kimberlites as constraints. The geotherm was adjusted back to 2.5 Ga by keeping the surface temperature constant and calculating the temperature change at the top of convecting upper mantle. The reduced or mantle heat flux, which was treated as an adjustable parameter, was 20.9–21.3 mW/m2 at 1–2.5 Ga. Comparison of the calculated steady-state geotherm with the available P-T data of the Archaean (c. 2.5 Ga) charnockites and granulites from southern India suggests that the granulite facies metamorphism in this region had resulted from a major thermal perturbation, which was c. 400° C at 25 km. Seismic tomographic and gravity data essentially preclude any significant magma underplating of the granulitic crust in southern India. Previous workers have suggested that the formation of charnockites in this region was associated with copious CO2 influx from a deep-seated source, possibly the mantle. In this work, we have evaluated both the transient and steady-state thermal effects of the heat convected by CO2 outgassing from upper mantle. It is shown that the thermobarometric array of charnockites and granulites can be produced by the convective perturbation of the steady-state geotherm, and that a flux of CO2 of ±90 mol/m2 yr (corresponding to Darcy velocity of ±0.30 cm/yr) for a period of ±30 Ma was needed to produce the required perturbation. This is c. 150 times the average CO2 flux through the tectonically active area of the Earth's crust at the present time. There is, however, an uncertainty of a factor of 3 in this value. Seismic tomographic and gravity data independently suggest thickening of the crust beneath the granulite terrane compared with the adjacent Dharwar craton. This suggests thermal perturbation due to overthrusting as a major potential cause for the granulite facies metamorphism in south India. Overthrusting of a 30–35-km-thick thrust block was needed to produce the required thermal effect. The estimated thickness of the original crust from geobarometric and seismic tomographic data south of the orthopyroxene isograd or ‘transition zone’is compatible with the emplacement of a thrust block of this magnitude. However, the latter fails to match the estimated pre-uplift crustal thickness at the transition zone, if it is assumed that the crust has not thinned by non-erosional processes since the Archaean. Thus, we propose a combination of overthrusting and CO2 fluxing from a deep-seated source as the cause for the formation of charnockites in this zone. The required focusing of CO2 in this case is c. 40% of that estimated in the model where CO2 fluxing was considered to be the sole reason for thermal perturbation. This combined thrusting—CO2 fluxing model also helps explain the development of patchy charnockites in the transition zone from amphibolite facies rocks. 相似文献
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