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1.
Occurrence of carbonatite is reported from the Munnar area, Kerala, where an alkali granite-syenite-carbonatite association is seen emplaced along the intersection zone of the Attur and Kerala fault-lineaments. The carbonatites are of two varieties, a calcite-rich sovite and a very coarse grained, calcite and dolomite bearing alvikite. Higher levels of SiO2, Al2O3 and CaO are characteristic of these as compared to the composition of typical carbonatites. The transition element levels are high whereas the incompatible elements show lower values. The low Sr values, lower amount of apatite and absence of rare metal minerals preclude a primary carbonatite magma. The associated syenite and alkali granite have higher K2O, K2O/Na2O, K/Rb, K/Ba and transition element levels. Petrochemical features suggest the rock association to be a result of separation of an immiscible fraction of less viscous carbonate liquid during cooling and ascent from a more viscous polymerized alkali silicate phase. The pre-requisites for melt equilibration and liquid immiscibility were achieved through volatile degassing related to crustal warping and rifting. The unique alkaline association of Munnar, which shows spatial relationships with deep-seated faults as well as a probable triple-point junction, is suggested to be a signature of late Precambrian alkaline magmatism which manifested in the Indian shield as a precursor to the rifting of the continental margin. 相似文献
2.
C. J. Thampi 《Journal of the Indian Society of Remote Sensing》1983,11(1):23-29
The paper discusses the use of Remote Sensing techniques for the integrated economic land use planning in Andaman and Nicobar Islands, agricultural land use being the main objective. Broad aspects of physiography, soil, land use etc. have been described. An idea about the soil environment and erosion hazards is given. A land use pattern on the basis of land capability and land suitability classification together with cropping pattern has been evolved and the model has been developed for the Island. 相似文献
3.
S. Abhilash Someshwar Das S. R. Kalsi M. Das Gupta K. Mohankumar John P. George S. K. Banerjee S. B. Thampi D. Pradhan 《Pure and Applied Geophysics》2007,164(8-9):1491-1509
Pre-monsoon rainfall around Kolkata (northeastern part of India) is mostly of convective origin as 80% of the seasonal rainfall
is produced by Mesoscale Convective Systems (MCS). Accurate prediction of the intensity and structure of these convective
cloud clusters becomes challenging, mostly because the convective clouds within these clusters are short lived and the inaccuracy
in the models initial state to represent the mesoscale details of the true atmospheric state. Besides the role in observing
the internal structure of the precipitating systems, Doppler Weather Radar (DWR) provides an important data source for mesoscale
and microscale weather analysis and forecasting. An attempt has been made to initialize the storm-scale numerical model using
retrieved wind fields from single Doppler radar. In the present study, Doppler wind velocities from the Kolkata Doppler weather
radar are assimilated into a mesoscale model, MM5 model using the three-dimensional variational data assimilation (3DVAR)
system for the prediction of intense convective events that occurred during 0600 UTC on 5 May and 0000 UTC on 7 May, 2005.
In order to evaluate the impact of the DWR wind data in simulating these severe storms, three experiments were carried out.
The results show that assimilation of Doppler radar wind data has a positive impact on the prediction of intensity, organization
and propagation of rain bands associated with these mesoscale convective systems. The assimilation system has to be modified
further to incorporate the radar reflectivity data so that simulation of the microphysical and thermodynamic structure of
these convective storms can be improved. 相似文献
4.
The sensitivity of heave response predictions for long riserless drill strings hanging from a floating vessel are examined. A general analytical procedure is presented which is suitable for a variety of deepwater pipe systems. The dynamic response behavior is characterized in terms of the dynamic magnification, phase angle and total stress. The examples presented here focus on drill string systems, which vary in length from 9000 ft (2743 m) to 27,000 ft (8230 m) and can include a large package to be lowered to the seafloor. A procedure for evaluating the undamped natural periods and the corresponding mode shapes is presented. The sensitivity of the natural period estimates to hydrodynamic added mass approximations is examined. Numerical results for both design wave and random sea simulations are used to illustrate the sensitivity of the dynamic response in near resonant conditions and the possibility of exciting higher modes for very long riserless drill string systems. Finally, the sensitivity of the displacement predictions to reasonable variations in skin friciton and viscous drag coefficients are presented and discussed. 相似文献
5.
Doppler weather radar based nowcasting of cyclone Ogni 总被引:3,自引:0,他引:3
Soma Sen Roy V. Lakshmanan S. K. Roy Bhowmik S. B. Thampi 《Journal of Earth System Science》2010,119(2):183-199
In this paper, we describe offline analysis of Indian Doppler Weather Radar (DWR) data from cyclone Ogni using a suite of
radar algorithms as implemented on NEXRAD and the advanced algorithms developed jointly by the National Severe Storms Laboratory
(NSSL) and the University of Oklahoma. We demonstrate the applicability of the various algorithms to Indian radar data, the
improvement in the quality control and evaluate the benefit of nowcasting capabilities in Indian conditions. New information
about the tropical cyclone structure, as derived from application of the algorithms is also discussed in this study. 相似文献
6.
G. Resmi Santosh G. Thampi S. Chandrakaran 《Journal of the Geological Society of India》2011,77(1):42-46
Clay liners are widely used as barriers to arrest the migration of pollutants. These liners are subjected to leaching of various
chemicals and hazardous wastes. Migration of heavy metals through the liner material may lead to changes in the soil properties
and this, in turn, may affect the performance of liners. In this paper, the change in index and engineering properties of
clayey soil due to migration of lead is presented. Pronounced changes in soil properties are noticed when the soil is contaminated
with high concentrations of lead. The findings from the present study are important while designing liners in landfills used
for containment of pollution due to heavy metals and hazardous wastes. 相似文献
7.
Analysis of contaminant transport through fractured crystalline rocks has received considerable attention, particularly with regard to subsurface nuclear waste repositories. Most of the studies have employed the dual continuum approach, with the fractures and the rock matrix as the two continuums, assuming that fractures control the overall conductivity of the rock and the porous matrix just provides storage. However, field observations of rock fractures have shown that the real situation can be very complex. Based on some recent investigations, it has been reported that the portion of the rock matrix adjacent to many open fractures is physically and chemically altered. These alterations, referred to as the fracture skin, can have different sorption and diffusion properties compared to those of the undisturbed rock matrix and this may influence the transport of solutes through such formations. In the present study, a numerical model is developed to simulate conservative solute transport in a fractured crystalline rock formation using the triple continuum approach ?? with the fracture, fracture skin and the rock matrix as the three continuums. The model is solved using a fully implicit finite difference scheme. Contaminant migration in the fractured formation with and without skin has been simulated. It is observed that contaminant penetration along the fracture is enhanced at large flow velocities. The effect of flow velocity on conservative solute transport is investigated for different fracture apertures and fracture skin thicknesses. The influence of flow velocity on contaminant transport is demonstrated to be more with change in fracture aperture than with change in skin thickness. 相似文献
8.
S. K. Roy Bhowmik Soma Sen Roy Kuldeep Srivastava B. Mukhopadhay S. B. Thampi Y. K. Reddy Hari Singh S. Venkateswarlu Sourav Adhikary 《Meteorology and Atmospheric Physics》2011,111(3-4):133-147
This paper demonstrates the usefulness of Indian Doppler Weather Radar (DWR) data for nowcasting applications, and assimilation into a mesoscale Numerical Weather Prediction (NWP) model. Warning Decision Support System Integrated Information (WDSS-II) developed by National Severe Storm Laboratory (NSSL) and Advanced Regional Prediction System (ARPS) developed at the Centre for Analysis and Prediction, University of Oklahoma are used for this purpose. The study reveals that the WDSS-II software is capable of detecting and removing anomalous propagation echoes from the Indian DWR data. The software can be used to track storm cells and mesocyclones through successive scans. Radar reflectivity mosaics are created for a land-falling tropical cyclone??Khaimuk of 14 November 2008 over the Bay of Bengal using observations from three DWR stations, namely, Visakhapatnam, Machilipatnam and Chennai. Assimilation of the quality-controlled radar data (DWR, Chennai) of the WDSS-II software in a very high-resolution NWP model (ARPS) has a positive impact for improving mesoscale prediction. This has been demonstrated for a land-falling tropical cyclone Nisha of 27 November 2008 of Tamil Nadu coast. This paper also discusses the optimum scan strategy and networking considerations. This work illustrates an important step of transforming research to operation. 相似文献
9.
Manoj Kumar Mishra K. Rajeev Bijoy V. Thampi K. Parameswaran Anish Kumar M. Nair 《Journal of Atmospheric and Solar》2010,72(17):1251-1259
A large aerosol plume with optical depth exceeding 0.7 engulfs most parts of the Arabian Sea during the Asian summer monsoon season. Based on Micro Pulse Lidar observations during the June–September period of 2008 and 2009, the present study depicts, for the first time, the existence of an elevated dust layer occurring very frequently in the altitude band of 1–3.5 km over the west coast of peninsular India with relatively large values of linear depolarization ratio (δL). Large values of δL indicate the dominance of significantly non-spherical aerosols. The aerosol optical depth of this layer (0.2) is comparable to that of the entire atmospheric column during dust-free days. Back-trajectory analysis clearly shows the advection of airmass from the arid regions of Arabia and the west Arabian Sea, through the altitude region centered around 3 km. This is in contrast to the airmass below 1 km originating from the pristine Indian Ocean region which contains relatively spherical aerosols of marine origin with δL generally <0.05. 相似文献