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Summary A study of the wavelength exponent of aerosol scattering in the Ångström relation for extinction by aerosol has been made from the ground-based measurments of direct solar radiation using Ångström pyrheliometer with and without Schott filters. It has been observed that in India, mainly for the middle part of the year this exponent is zero or even negative which means that the aerosol scattering is nearly neutral which is in marked contrast with the condition prevailing in middle latitudes. It is evident from the -values that the aerosol size distribution in India is far different from that prevailing in middle latitudes. At four representative stations in India, the values of the wavelength exponent and the atmospheric turbidity coefficient have been determined using the method introduced byÅngström [1,2]) and are discussed here. 相似文献
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Though entropy production is forbidden in standard FRW Cosmology, Berman and Som presented a simple inflationary model where
entropy production by bulk viscosity, during standard inflation without ad hoc pressure terms can be accommodated with Robertson–Walker’s
metric, so the requirement that the early Universe be anisotropic is not essential in order to have entropy growth during
inflationary phase, as we show. Entropy also grows due to shear viscosity, for the anisotropic case. The intrinsically inflationary
metric that we propose can be thought of as defining a polarized vacuum, and leads directly to the desired effects without
the need of introducing extra pressure terms. 相似文献
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Optical constants in a broad temperature and wavelength range are important input parameters in radiative transfer models used in studies of planetary atmospheres. In the laboratory, the refractive index values of ices at the HeNe laser wavelength (632.8 nm) are often used to monitor the growth rate and thickness of ice films. In this report we present laboratory measurements determining the refractive index at 632.8 nm of ammonia and hydrocarbon ices in the temperature range 80-100 K. Thin ice films are vapor-deposited on a cryogenically cooled mirror located inside a high-vacuum apparatus. The real component of the refractive index of these ice films is determined by a two-angle interferometric technique. Optical modeling calculations of the transmittance and reflectance through the thin ice films assist in the interpretation of the experimental results. We discuss our results and compare them with other measurements available in the literature. The results reported here are relevant to the spectroscopy of icy objects in the solar system; they are needed to perform laboratory characterization of ices, derive optical constants, and model spectra. 相似文献
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Geomorphology,sedimentology and minimum exposure ages of streamlined subglacial landforms in the NW Himalaya,India 
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下载免费PDF全文 Sourav Saha Milap C. Sharma Madhav K. Murari Lewis A. Owen Marc W. Caffee 《Boreas: An International Journal of Quaternary Research》2016,45(2):284-303
Streamlined subglacial landforms that include drumlins in three study areas, the upper Chandra valley around Chandra Tal, the upper Spiti Valley and the middle Yunam Valley of the NW Himalaya of India were mapped and studied using geomorphic, sedimentological and geochronological methods. These streamlined subglacial landforms include a variety of morphological types, including: (i) half egg‐shaped forms; (ii) complex superimposed forms; (iii) dome‐shaped forms; (iv) inverse forms; and (v) flat‐topped symmetrical forms. Sedimentological data indicate that subglacial deformational processes are responsible for the formation of the streamlined subglacial landforms in the Chandra Tal and upper Spiti Valley study areas. In contrast, streamlined landforms in the middle Yunam Valley are the result of melt‐out and subglacial erosional processes. In the Yunam Valley study area, 11 new cosmogenic 10Be surface exposure ages were obtained for boulders inset into the crests of streamlined subglacial landforms and moraines, and also for a bedrock surface. The streamlined landforms date to 8–7 ka, providing evidence of an early Holocene valley glaciation, and older moraines date to ～17–15 and 79–52 ka, representing other significant valley glacial advances in the middle Yunam Valley. The subglacial landforms in the Chandra Valley provide evidence for a ≥300‐m‐thick Lateglacial glacier that advanced southeast, overtopping the Kunzum Range, and advancing into the upper Spiti Valley. The streamlined subglacial landforms in these study areas of the NW Himalaya highlight the usefulness of such landforms in developing glacial chronostratigraphy and for understanding the dynamics of Himalayan glaciation. 相似文献
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Jean Riotte Laurent Ruiz Stéphane Audry Benjamin Baud Jean-Pierre Bedimo Bedimo Laurie Boithias Jean-Jacques Braun Bernard Dupré Jean-Louis Duprey Mikael Faucheux Christelle Lagane Jean-Christophe Marechal Hemanth Moger Mandalagiri Subbarayappa Mohan Kumar Harshad Parate Olivier Ribolzi Emma Rochelle-Newall Buvaneshwari Sriramulu Murari Varma Muddu Sekhar 《水文研究》2021,35(5):e14196
Despite the importance of tropical ecosystems for climate regulation, biodiversity, water and nutrient cycles, only a few Critical Zone Observatories (CZOs) are located in the tropics. Among these, most are in humid climates, while very few data exist for semi-arid and sub-humid climates, due to the difficulty of estimating hydro-geochemical balances in catchments with ephemeral streams. We contribute to fill this gap by presenting a meteorological and hydro-geochemical dataset acquired at the Mule Hole catchment (4.1 km2), a pristine dry deciduous forest located in a biosphere reserve in south India. The dataset consists of time series of variables related to (i) meteorology, including rainfall, air temperature, relative humidity, wind speed and direction, and global radiation, (ii) hydrology, including water level and discharge at the catchment outlet, (iii) hydrogeology, including manual (monthly) and/or automated (from 15 min to hourly) groundwater levels in nine piezometers and (iv) geochemistry, including suspended sediment content in the stream and chemical composition of rainfall (event based), groundwater (monthly sampling) and stream water (storm events, 15 min to hourly frequency with an automatic sampler). The time series extend from 2003 to 2019. Measurement errors are minimized by frequent calibration of sensors and quality checks, both in the field and in the laboratory. Despite these precautions, several data gaps exist, due to occasional access restriction to the site and instrument destruction by wildlife. Results show that large seasonal and interannual variations of climatic conditions were reflected in the large variations of stream flow and groundwater recharge, as well as in water chemical composition. Notably, they reveal a long-term evolution of groundwater storage, suggesting hydrogeological cycles on a decadal scale. This dataset, alone or in combination with other data, has already allowed to better understand water and element cycling in tropical dry forests, and the role of forest diversity on biogeochemical cycles. As tropical ecosystems are underrepresented by Critical Zone Observatories, we expect this data note to be valuable for the global scientific community. 相似文献
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N. P. Honkanadavar Nripendra Kumar Murari Ratnam 《Geotechnical and Geological Engineering》2014,32(4):1001-1015
Two types of modeled rockfill materials were collected from Renuka dam site, Himachal Pradesh, India and Salma dam site, Afghanistan. The rockfill material collected from Renuka dam site is rounded to sub-rounded in shape and the rockfill material collected from Salma dam site is angular to sub-angular in shape. The prototype gradation rockfill material consists maximum particle size larger than 1,000 mm. Therefore, for carrying out laboratory testing and modeling the bahaviour, the prototype rockfill material is scaled down to the maximum particle size (dmax) of 25, 50 and 80 mm for both projects material using parallel gradation technique. Triaxial compression and Index properties tests were conducted on both project rockfill materials and are presented. From the triaxial behaviour, it is observed that the stress–strain behaviour is non-linear, inelastic and stress dependent for both the materials. The material compresses during the initial shearing and shows dilation effect with further shearing. It is observed that the ?-value for alluvial rockfill material increases with increase in dmax and reverse trend is observed for blasted quarried rockfill material which shows the importance of the type of material. The stress–strain-volume change behaviour of both projects modeled rockfill material was predicted by using hierarchical single surface (HISS) model based on elasto plasticity and compared with the laboratory test results. From the comparison, it is observed that both results match closely. It is, therefore, suggested that the behaviour of both types of rockfill materials can be characterized successfully using HISS model. 相似文献
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R. Jayangondaperumal M.K. Murari P. Sivasubramanian N. Chandrasekar A.K. Singhvi 《Quaternary Research》2012,77(3):468-481
The Holocene and late Pleistocene environmental history of the teri (‘sandy waste’ in local parlance) red sands in the southeast coastal Tamil Nadu was examined using remote sensing, stratigraphy, and optically stimulated luminescence (OSL) dating. Geomorphological surveys enabled the classification of the teri red sands as, 1) inland fluvial teri, 2) coastal teri and, 3) near-coastal teri dunes. The inland teri sediments have higher clay and silty-sand component than the coastal and near-coastal teri, suggesting that these sediments were deposited by the fluvial process during a stronger winter monsoon around > 15 ka. The coastal teri dunes were deposited prior to 11.4 ± 0.9 ka, and the near-coastal dunes aggraded at around 5.6 ± 0.4 ka. We interpret that the coastal dunes were formed during a period of lower relative sea level and the near-coastal dunes formed during a period of higher sea level. Dune reddening is post deposition occurred after 11.4 ± 0.9 ka for the coastal teri dunes and after 5.6 ± 0.4 ka for the near-coastal teri dunes. Presence of microlithic sites associated with the coastal dunes suggest that the cultures existed in the region during 11.4 ± 0.9 ka and 5.6 ± 0.4 ka. 相似文献