Geographic information system–based morphometric characterization of sub-watersheds of Meenachil river basin,Kottayam district,Kerala, India     

M.V. Vincy  Brilliant Rajan  A.P. Pradeepkumar 《国际地球制图》2013,28(8):661-684

The study areas Tikovil and Payppara sub-watersheds of Meenachil river cover 158.9 and 111.9 km², respectively. These watersheds are parts of Western Ghats, which is an ecologically sensitive region. The drainage network of the sub-watersheds was delineated using SOI topographical maps on 1:50,000 scale using the Arc GIS software. The stream orders were calculated using the method proposed by Strahler's (1964 Strahler, A. N. 1964. “Quantitative geomorphology of drainage basins and channel networks”. In Hand book of applied hydrology. Vol. 4, Edited by: Chow, V. T. Vol. 4, 39–44.  [Google Scholar]). The drainage network shows that the terrain exhibits dendritic to sub-dendritic drainage pattern. Stream order ranges from the fifth to the sixth order. Drainage density varies between 1.69 and 2.62 km/km². The drainage texture of the drainage basins are 2.3 km^–1 and 6.98 km^–1 and categorized as coarse to very fine texture. Stream frequency is low in the case of Payappara sub-watershed (1.78 km^–2). Payappara sub-watershed has the highest constant of channel maintenance value of 0.59 indicating much fewer structural disturbances and fewer runoff conditions. The form factor value varies in between 0.42 and 0.55 suggesting elongated shape formed for Payappara sub-watershed and a rather more circular shape for Tikovil sub-watershed. The mean bifurcation ratio (3.5) indicates that both the sub-watersheds are within the natural stream system. Hence from the study it can be concluded that GIS techniques prove to be a competent tool in morphometric analysis.  相似文献   

Providing new homes for climate change exiles     

Sujatha Byravan  Sudhir Chella Rajan 《Climate Policy》2013,13(2):247-252

Abstract

Given a certain pre-existing commitment to sea-level rise due to the long thermal lags of the ocean system, several million people living in coastal areas and small islands will inevitably be displaced by the middle of the century. These climate exiles will have nowhere to go. Rather than deal with this in an ad hoc manner as the problem arises, the authors propose a mechanism by which these exiles would be given immigration benefits by countries through a formula that ties numbers of immigrants to a country's historical greenhouse gas emissions. Such a compensatory mechanism appears to be a fair way of addressing the problems faced by climate exiles.  相似文献   

Inversion for the compressional wave speed profile of the bottomfrom synthetic aperture experiments conducted in the Hudson Canyon area     

Rajan  S.D. Doutt  J.A. Carey  W.M. 《Oceanic Engineering, IEEE Journal of》1998,23(3):174-187

In September 1988, a series of acoustic propagation experiments were conducted in the Hudson Canyon area. These included synthetic aperture experiments in which a source transmitting a set of four pure tones was towed toward/away from a vertical array of 24 receivers. Data obtained at 50 Hz during one of the synthetic aperture experiments are used to obtain a model for the compressional wave speed profile in the bottom using a modal inverse method. This model is further refined using 175 Hz data. The ability of the inferred model to predict the field at 50 Hz and higher frequencies is examined  相似文献   

Post-stack seismic inversion and attribute analysis in shallow offshore of Krishna-Godavari basin,India     

Baisakhi Das  Rima Chatterjee  Dip Kumar Singha  Rajan Kumar 《Journal of the Geological Society of India》2017,90(1):32-40

Seismic attributes such as: amplitude envelope, instantaneous phase and cosine of instantaneous phase of 2D post-stack seismic data facilitates structural and stratigraphic interpretation of shallow marine offshore, Krishna-Godavari basin. Two seismic sections namely, X and Y oriented N-S passing through wells W-1 andW-2 respectively are considered for seismic attribute analysis and porosity prediction. The gamma ray log trend indicates deposition of cleaning upward sediment. Coarsening upward, clayey-silty-sandy bodies, making a series of about 50-60 m thickness, have been evidenced from the gamma ray log. An extensional structural style comprising growth faults is associated with the progradational style of deposition. Four seismic zones have been distinguished. These zones differ in amplitude, frequency and continuity of the reflectors. Channel sands of Cretaceous age of Raghavapuram shale are identified in well log, seismic section and its acoustic impedance section. Major stratigraphic horizons along with faults extending to basement are marked with the help of attribute analysis. Porosity is mapped from transformation of acoustic impedance. The shales/unconsolidated sediments measure a high porosity with low impedance and the more porous sands are in an intermediate range. The predicted impedance and porosity values may be erroneous beyond the drilled depth because of non availability of well log data for calibration.  相似文献   

Effect of the variation in the lower tropospheric temperature on the wind onset of the Indian summer monsoon     

Kenji Taniguchi  Devraj Rajan  Toshio Koike 《Meteorology and Atmospheric Physics》2010,106(1-2):75-94

There is a large thermal contrast between the Arabian Peninsula and India (Δθ _AI) at the mature stage of the Indian summer monsoon (ISM). The forming process of Δθ _AI is investigated analyzing various datasets. It forms earlier in the lower troposphere than in the middle and upper layers. The potential temperature in the lower troposphere over the west coast of India (θ _IW) abruptly decreases in advance of the rapid enhancement of the westerly wind over the Arabian Sea corresponding to the ISM onset. Such a process was observed for all the target years and the rapid decrease in θ _IW could trigger the ISM onset. The decrease in θ _IW had two patterns. In one case, cooler air is brought by the strong winds around a cyclone over the Arabian Sea. In another case, θ _IW decreases gradually by a synergy of a southwesterly wind over the Arabian Sea and the enlargement of Δθ _AI.  相似文献   

Study of cloud liquid water path and total precipitable water from irs-p4/msmr and numerical weather prediction model output     

S.?Das  A.?S.?K.?A.?V.?Prasad?Rao  U.?C.?MohantyEmail author  A.?K.?Mitra  D.?Rajan 《Journal of the Indian Society of Remote Sensing》2004,32(2):175-184

A global weather analysis-forecast system is used to produce six hourly analysis of meteorological fields at roughly 150 km × 150 km resolution at the National Center for Medium Range Weather Forecast (NCMRWF). In this paper, we have studied the Total Precipitable Water Content (TPWC) and Cloud Liquid Water Path (CLWP) derived from the Indian Remote Sensing (IRS-P4) Satellite over the Indian Ocean region in relation to operational numerical weather prediction (NWP) model analysis and short-range forecasts. An objective analysis was carried out by introducing the observations of CLWP, TPWC and their values (six hour forecasts) from the T80 model as the first guess, for a 20 days period of August 1999 using the standard Cressman’s technique. The reanalysis could capture the signature of TPWC and CLWP data from IRS-P4 satellite. In general the observed values of TPWC and CLWP from IRS-P4 have a positive bias compared to NCMRWF analysis over the region where the satellite passed. The CLWP values have been compared with Special Sensor Microwave/Imager (SSM/I) products from the Defense Meteorological Satellite Program (DMSP) satellites. Results indicate that the model derived CLWP values were within acceptable limits, whereas the observations from the Multi-channel Scanning Microwave Radiometer (MSMR) showed slightly larger values.  相似文献   

Exploration and Research for Atomic Minerals     

K.D.P. Singh  D. Narasimhan  P. Rajasekaran  Rajan B. Jain 《Gondwana Research》2005,8(4):637

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Chondrule-like objects and brown glasses in howardites     

Edward J. Olsen  Kurt Fredriksson  Sundar Rajan  Albert Noonan 《Meteoritics & planetary science》1990,25(3):187-194

Abstract— Chondrule-like objects and brown glasses were analyzed in the howardites, Bununu, Malvern, Monticello, Pavlovka, and Yamato 7308. The objects are very similar to chondrules in ordinary and carbonaceous chondrites. Like the brown glasses the chondrule-like objects could have been produced by impact melting that left some crystalline nuclei, followed by a slower cooling rate than for the glasses. Alternatively, these objects are chondrules implanted from chondrite impactors. They are, however, without rims or any adhering matrix. The brown glasses appear to represent melting of average regolithic surface material, except for Monticello and Y7308, both of which have some siliceous glasses. The siliceous glasses could not have been produced by vapor fractionation but by melting of differentiated lithologies such as fayalitic granites. Impact mechanics indicates that howardites with abundant brown glasses came from an asteroid larger than Vesta (>400 km radius), upon which impacts occurred at relative velocities of up to 5 km/s. Howardites with little or no brown glasses came from a smaller parent body. We conclude that at least two parent bodies are likely sources for the basaltic achondrites.  相似文献   

Neon and argon in the Allende meteorite     

S.P Smith  J.C Huneke  R.S Rajan  G.J Wasserburg 《Geochimica et cosmochimica acta》1977,41(5):627-647

Trapped and cosmogenic Ne and Ar were measured in Ca,Al-rich aggregates and chondrules, mafic chondrules, and bulk and matrix samples from the Allende C3V chondritic meteorite to investigate the possible occurrence of anomalous isotopic compositions of noble gases that would correlate with oxygen or magnesium isotopic anomalies previously found in this meteorite.Large enrichments of both ²²Ne and ³⁶Ar were observed in low-temperature release fractions from several Ca,Al-rich inclusions, but the enrichments are consistent with galactic cosmic-ray production of ²²Ne by spallation from sodium and ³⁶Ar by neutron capture on chlorine. Trapped neon in matrix samples is comprised of two distinctive compositions, with (²⁰Ne/²²Ne)_t equal to 8.7 ± 0.1 and 10.4 ± 1.0, that appear to correlate with the two gas-rich trace phases chromite/carbon and ‘Q’ described by Lewis et al. (1975). Several Ca,Al-rich aggregates which have high contents of the volatile elements Na, Cl, K, and Rb also contain trapped neon. However, no neon-E has been identified in any of the samples studied, including samples of several inclusions known to contain isotopically anomalous oxygen and magnesium.  相似文献   

Chondrules in the Qingzhen type-3 enstatite chondrite: Possible precursor components and comparison to ordinary chondrite chondrules     

Jeffrey N. Grossman  Alan E. Rubin  Ermanno R. Rambaldi  R.Sundar Rajan  John T. Wasson 《Geochimica et cosmochimica acta》1985,49(8):1781-1795

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