Strontium isotope and alkali element abundances in ultramafic rocks     

Alan M. Stueber  V. Rama Murthy 《Geochimica et cosmochimica acta》1966,30(12):1243-1259

The concentrations of the trace elements Na, K, Rb and Sr and the isotopic composition of Sr have been measured in a suite of ultramafic rocks, including alpine-type intrusions, inclusions in basalts and kimberlite pipes, zones from stratiform sheets, and a mica peridotite. From these data and those available in the literature the following conclusions can be drawn. Alpine-type ultramafic material appears to be residual in nature and can be neither the source material for the derivation of basalts nor the refractory residue of modern basalts. Alpine-type ultramafic intrusions appear to have no relationship with ultramafic zones in stratiform sheets and were probably derived from the upper mantle. A genetic relationship exists between basalts and their ultramafic inclusions, but it is extremely doubtful that this inclusion material could give rise to basalts by partial fusion. There is a possible genetic relationship between basalts and ultramafic inclusions in kimberlite pipes, and this ultramafic material is a potential source for the derivation of basalts. Ultramafic inclusions in basalts are probably not fragments of an alpine-type ultramafic zone in the mantle. An attempt has been made to synthesize the data and interpretations of this study by way of speculations on the role of ultramafic rocks in the differentiation history of the earth.  相似文献   

A search for correlation between seismicity and radon anomaly in hot springs     

B S Amin  Rama 《Journal of Earth System Science》1982,91(1):15-19

Measurements of radon contents of the exholved gas emanating from several hot water springs along the Western Coast of India are reported here. Concentration of radon in gas phase of individual springs varied in general, directly with the surface temperature of the water emerging from the respective springs, and showed little variation with time. Radon measurements were carried out continuously for about two years at two hot springs located at Ganeshpuri and Sathivali in the coastal area of Northern Maharashtra. The distant tremors did not cause any variation in the radon content. There was no marked local seismic activity during the period of observations, and the levels of radon stayed essentially constant. The measurements were also carried out at a hot spring in Assam, for about 8 months. These also did not show any significant variation; this period too lacked any marked local seismicity.  相似文献   

Strontium isotope geochemistry of alpine tectonite lherzolites: Data compatible with a mantle origin     

Martin M. Menzies  V. Rama Murthy 《Earth and Planetary Science Letters》1978,38(2):346-354

Constituent minerals from three alpine lherzolites (Beni Bouchera, Morocco; Lanzo, Italy; and Ronda, Spain) and a clinopyroxene from the Othris complex, Greece, reveal the following range in Sr isotopic composition: clinopyroxenes, 0.70228–0.70370; orthopyroxenes, 0.70265–0.70429; and olivines, 0.70290–0.70831. Collectively the data: (1) indicate that whole-rock lherzolites (weighted recalculations of ⁸⁷Sr/⁸⁶Sr= 0.7025–0.7028) have isotopic compositions which attest to a simple mantle origin and not the complex models proposed to date; (2) are incompatible with the published range for alpine peridotites 0.7063–0.7290; (3) reveal either similar or different isotopic compositions for coexisting minerals, the latter possibly being the result of Rb mobility and introduction of radiogenic Sr into the peridotite system; and (4) indicate the past existence of liquids with “alkalic” affinities within the lherzolite framework. The lherzolites are therefore believed to be residual, having experienced a small degree of partial melting.  相似文献   

Palaeo-tectonic environment of the Precambrian basaltic mafic dykes on the application of chemical discriminants     

T. Ramamohana Rao  B. V. Satyanarayana Raju  M. V. Rama Raju 《Journal of Earth System Science》1986,95(3):351-361

Dykes of Chitaldurg and Newer Dolerite I are OFB and represent early attempts to rift and to generate oceanic crust. Shimoga dykes are CAB and belong to orogenic phase. Guntur dykes and Ananthapur-Chittoor dykes are OIB and these are related to ‘hot spot’. Newer Dolerite II is CONB and belongs to healing and filling of fractured crust. The Cuddapah dykes are transitional to all magma types and these represent a compound event of rifting and filling of fractured continental crust.  相似文献   

Spectral reflectance studies on certain fuel wood species     

P. H. V. Vasudeva Rao  E. Amminedu  S. Sudhakar  B. V. Nageswara Rao  R. V. Rama Rao 《Journal of the Indian Society of Remote Sensing》1987,15(2):13-21

Spectral reflectance studies are carried out on certain fuel wood species with reference to IRS bands 1, 2, 3 and 4. The reflectance values are correlated with different types of soil substratum, spacing and leaf area index. The radiometric responses of adaxial and abaxial surfaces of leaves, reflectance from canopy and transmittance through canopy are studied. Variations in the values are discussed in relation to the above parameters.  相似文献   

Spectral responses of jojoba under salinity stress     

P. H. V. Vasudeva Rao  E. Amminedu  R. V. Rama Rao 《Journal of the Indian Society of Remote Sensing》2000,28(4):281-291

Spectral reflectance characteristics of jojoba (Simmondsia chinensis (Link) Schneid.), a dioecious member of Buxaceae have been studied, especially under salinity stress. Reflectance is minimum at bands 1 and 2 (450–520 nm and 520–590 run) of visible range and maximum at bands 3 and 4 (620–680 nm and 770–860 nm) of near infrared range. At all wavelength intervals, male plants have greater reflectance than females. Reflectance in near infrared range (band 4) decreases with increasing age and leaf area index (LAI). A reverse trend occurs at band 3. Absorptance increases in visible as well as Infrared ranges with increasing salinity from control to 10 PSU of sea water concentration.  相似文献   

Albedo enhancement of marine clouds to counteract global warming: impacts on the hydrological cycle     

G. Bala  Ken Caldeira  Rama Nemani  Long Cao  George Ban-Weiss  Ho-Jeong Shin 《Climate Dynamics》2011,37(5-6):915-931

Recent studies have shown that changes in solar radiation affect the hydrological cycle more strongly than equivalent CO₂ changes for the same change in global mean surface temperature. Thus, solar radiation management ??geoengineering?? proposals to completely offset global mean temperature increases by reducing the amount of absorbed sunlight might be expected to slow the global water cycle and reduce runoff over land. However, proposed countering of global warming by increasing the albedo of marine clouds would reduce surface solar radiation only over the oceans. Here, for an idealized scenario, we analyze the response of temperature and the hydrological cycle to increased reflection by clouds over the ocean using an atmospheric general circulation model coupled to a mixed layer ocean model. When cloud droplets are reduced in size over all oceans uniformly to offset the temperature increase from a doubling of atmospheric CO₂, the global-mean precipitation and evaporation decreases by about 1.3% but runoff over land increases by 7.5% primarily due to increases over tropical land. In the model, more reflective marine clouds cool the atmospheric column over ocean. The result is a sinking motion over oceans and upward motion over land. We attribute the increased runoff over land to this increased upward motion over land when marine clouds are made more reflective. Our results suggest that, in contrast to other proposals to increase planetary albedo, offsetting mean global warming by reducing marine cloud droplet size does not necessarily lead to a drying, on average, of the continents. However, we note that the changes in precipitation, evaporation and P-E are dominated by small but significant areas, and given the highly idealized nature of this study, a more thorough and broader assessment would be required for proposals of altering marine cloud properties on a large scale.  相似文献   

Numerical simulation of cloud burst event on August 05, 2010, over Leh using WRF mesoscale model   总被引：1，自引：1，他引：0  

M. Sravana Kumar  M. S. Shekhar  S. S. V. S. Rama Krishna  M. R. Bhutiyani  A. Ganju 《Natural Hazards》2012,62(3):1261-1271

Localized deep cumulus convective clouds have a capability of giving enormous amount of rainfall over a limited horizontal area, within a short span of time. Such types of extreme rainfall events are most common over the high elevated areas of Northern India during the Southwest monsoon season which causes widespread damage to the property and lives. Therefore, it is necessary to predict such extreme events accurately to avoid damage associated with them. The numerical mesoscale model Weather Research and Forecasting has been used to simulate the cloud burst event of Leh on August 05, 2010, so as to capture the main characteristics of the various parameters associated with this localized mesoscale phenomenon. The model has been integrated with four nested domains keeping Leh and its adjoining area as center. Two cloud microphysics parameterization schemes namely WSM3 and WSM6 have been used for the sensitivity experiments and results have been analyzed to examine the performance of both the schemes in capturing such extreme localized heavy rainfall events. Results show that the WSM6 microphysics was able to simulate the precipitation near to the observation. WSM3 microphysics simulated the location of the circulation near to the observation. In addition, the results also show that the maximum magnitudes of meridional and vertical wind as simulated with WSM3 microphysics are 12 and 4 m/s, respectively.  相似文献   

Layered clouds in the Indian monsoon region     

M. K. Rama Varma Raja  G. C. Asnani  P. S. Salvekar  A. R. Jain  D. Narayana Rao  S. Venkoba Rao  P. Kishore  M. Hareesh 《Journal of Earth System Science》1999,108(4):287-295

Contrary to the prevalent belief that tropical region is characterized by convective clouds rather than by layer clouds, we have suggested that deep convective clouds occur on meso-scale, but layer clouds occur on larger synoptic-scale with a relatively small region of deep convective clouds. Sustenance of deep convective clouds is inhibited by the presence of inertio-gravity waves, which have alternating layers of upward and downward motion in the vertical. We have also shown that inertio-gravity waves generate regions of relatively strong horizontal velocity, vertically separated by layers of relatively weak horizontal velocity. Layers of strong horizontal velocity are created by inertio-gravity wave system through convergence of vertical flux of horizontal momentum. We have also suggested that horizontal convergence/divergence of moisture flux is generated by inertio-gravity waves, giving rise to vertically alternating layers of high/low humidity, and visible or sub-visible clouds. Layers of high humidity become layers of strong radar reflectivity at frequency of 53 MHz at which MST Radar at Gadanki, near Tirupati, India, operates. These observations, more than 2,50,000 in number, for vertical grid points, spread over all the months of the year, have helped us, among other observations, to arrive at these conclusions. Further, the analysis suggests that the main source of strong MST radar reflectivity is not mechanical turbulence as is commonly believed.  相似文献   

Size segregated aerosol mass concentration measurements over the Arabian Sea during ICARB     

Vijayakumar S. Nair  K. Krishna Moorthy  S. Suresh Babu  K. Narasimhulu  L. Siva Sankara Reddy  R. Ramakrishna Reddy  K. Rama Gopal  V. Sreekanth  B. L. Madhavan  K. Niranjan 《Journal of Earth System Science》2008,117(1):315-323

Mass concentration and mass size distribution of total (composite) aerosols near the surface are essential inputs needed in developing aerosol models for radiative forcing estimation as well as to infer the environment and air quality. Using extensive measurements onboard the oceanographic research vessel, Sagar Kanya, during its cruise SK223B in the second phase of the ocean segment of the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB), the spatial distribution of the mass concentration and mass size distribution of near-surface aerosols are examined for the first time over the entire Arabian Sea, going as far as 58°E and 22°N, within a span of 26 days. In general, the mass concentrations (M _T ) were found to be low with the mean value for the entire Arabian Sea being 16.7 ± 7 μg m^?3; almost 1/2 of the values reported in some of the earlier campaigns. Coarse mode aerosols contributed, on an average, 58% to the total mass, even though at a few pockets accumulation mode contribution dominated. Spatially, significant variations were observed over central and northern Arabian Sea as well as close to the west coast of India. In central Arabian Sea, even though the M _T was quite low, contribution ofs accumulation aerosols to the total mass concentration was greater than 50%. Effective radius, a parameter important in determining scattering properties of aerosol size distribution, varied between 0.07 and 0.4 μm with a mean value of 0.2 μm. Number size distributions, deduced from the mass size distributions, were approximated to inverse power-law form and the size indices (ν) were estimated. It was found to vary in the range 3.9 to 4.2 with a mean value of 4.0 for the entire oceanic region. Extinction coefficients, estimated using the number-size distributions, were well-correlated with the accumulation mode mass concentration with a correlation coefficient of 0.82.  相似文献