Sensitivity of Tropical Cyclone Intensity and Structure to Planetary Boundary Layer Parameterization     

Deepika Rai  Sandeep Pattnaik 《Asia-Pacific Journal of Atmospheric Sciences》2018,54(3):473-488

The advanced weather research and forecasting model is used to investigate the influence of planetary boundary layer (PBL) processes on intensity and structure of the storm Phailin (2013). Five simulations are conducted with five PBL schemes; Yonsei University (YSU), Mellor?Yamada?Nakanishi?Niino order2.5 (MYNN2), Assymetric Convective Model2 (ACM2), Medium Range Forecast (MRF), and Bougeault and Lacarrere (BouLac). The simulation duration includes the pre???intensification and rapid intensification phase of Phailin before landfall. Results indicate that during the pre???intensification phase, storm’s track and intensity are not much sensitivity to PBL but structural changes are noted. A significant sensitivity of track and intensity to PBL parameterizations are found during rapid intensification phase. BouLac and MRF produced two extremes with 39 hPa intense and 16 km compact storm for BouLac than MRF. Further analysis reveals an outward movement of air parcel just above the boundary layer which causes spin-down for YSU and MYNN2. BouLac is associated with stronger eddy diffusivity and moisture fluxes within the boundary layer and stronger cyclonic vorticity just above the boundary layer than other experiments. Stronger cyclonic vorticity above the boundary layer in BouLac favors intense updraft, facilitating more moisture transport from the boundary layer to upper layers aiding stronger secondary circulation and robustly intensifying the storm. A relatively deeper and drier inflow layer associated with weaker cyclonic vorticity just above the boundary layer reduces the moisture transport and weaken the secondary circulation for MRF than others.  相似文献   

Optimization and biokinetic studies on pretreatment of sludge for enhancing biogas production     

P. Divyalakshmi  D. Murugan  M. Sivarajan  A. Sivasamy  P. Saravanan  C. L. Rai 《International Journal of Environmental Science and Technology》2017,14(4):813-822

Excess sludge generation is a major problem in biological effluent treatment processes. Utilization of excess sludge for gas production is an attractive route, which could be enhanced by pretreatment methods. This study involves two sets of experiments. The first set covers mechanical pretreatment of both feed and inoculum. The second set involves alkaline and mechanical treatments of feed and only mechanical treatment of inoculum. Response surface methodology was used for experimental design, analysis and optimization. The optimized mechanical treatment volume of feed was found to be 50%. Diligent mechanical treatment of inoculum resulted in enhanced microbial activity and improved gas production. Reduction in volatile solids, proteins and carbohydrates was observed to a maximum of 63, 84 and 78.5%, respectively. Feed was subjected to alkali treatment in order to reduce mechanical energy input and to improve solubilization. Compared to mechanical treatment alone, enhanced gas production of about 15% was observed at an optimized pH of 11.8 and SRT of 21 days. A biokinetic model was formulated, simulated and validated for the degradation of organics and gas production.  相似文献   

Estimation of snow and glacial melt contribution through stable isotopes and assessment of its impact on river morphology through stream power approach in two Himalayan river basins     

L. Sardine Varay  S. P. Rai  S. K. Singh  Vikrant Jain 《Environmental Earth Sciences》2017,76(23):809

The impact of increased temperature on the Third Pole, as the Himalayas is referred to, and the likely cascading impacts on the general downstream hydrology have been widely noted. However, the impact on fluvial geomorphology has not received specific attention. Change in the glacial domain in terms of melt increase will change discharge and sediment flux into fluvial system, which will induce changes in fluvial processes and forms. The present work attempts to study this process-based glacio-fluvial coupling in the two neighbouring glaciated river basins in the Northwest Himalaya, viz., the Sutlej and the Yamuna river basins till the mountain front. A total of 194 samples of river, tributary and groundwater of pre- and post-monsoon seasons in the two river basins were analysed for stable isotopes. The trend of δ¹⁸O and electrical conductivity along the mainstream gives qualitative idea on the influence of headwaters in the downstream of the catchment thereby allowing inference on melt contribution. Further, two component mixing model using stable oxygen isotope of two seasons water samples showed that melt contributes about 41.1–66.8 and 6.6–10.6% at different points to the total river discharge in the Sutlej and the Tons River (the glaciated, major tributary of the Yamuna River) basins, respectively. For different scenarios of increase in melt, stream power increase in the Sutlej River basin is significant as opposed to the Tons River. River channel in the Sutlej River basin will be significantly more impacted in comparison with the Yamuna River system.  相似文献   

Magnetic and radiometric signatures over a Proterozoic massive sulfide setting of northern fringe of Dalma Volcanics,eastern India: An implication to metallogeny     

Pramod Kumar Yadav  P. K. Adhikari  Shalivahan  Anurag Tripathi  Shailendra Singh  Roshan K. Singh  Ashish K. Bage 《Journal of the Geological Society of India》2017,89(6):705-710

Magnetic and radiometric surveys were carried out over a felsic dominated rifted margin of Proterozoic volcanic terrain of a mobile belt in the eastern India. The studies were made in blocks I and II of 0.65 sq km and 0.70 sq km respectively over a previously identified conductor in the northern fringe of Dalma Volcanics (DVs). In general, both the blocks show high magnetic signature associated with sulfide mineralisation. The interpretation of magnetic data suggests that nature of the causative source is mainly horizontal cylinder in both the blocks. The depth to the top of the causative source is about 25 m in both the blocks and extends upto 60 m in block I and 40m in block II. Gamma count rate exhibits about a factor of two to three enhancements above the field background for both the blocks. The obtained iso-rad maps are similar to uranium and copper belt in the Singhbhum shear zone south of the study area. The anomalous radiometric signature of the residual soil/rock of the area indicates towards hydrothermal alteration. The detailed magnetic surveys and preliminary iso-rads results seems quite encouraging and may be attributed to VMS setting in the area and potential sulfide mineralisation with uranium mineral association in the DVs province.  相似文献   

In‐plane and out‐of‐plane behavior of confined masonry walls for various toothing and openings details and prediction of their strength and stiffness          下载免费PDF全文

Vaibhav Singhal  Durgesh C. Rai 《地震工程与结构动力学》2016,45(15):2551-2569

Eight half‐scale brick masonry walls were tested to study two important aspects of confined masonry (CM) walls related to its seismic behavior under in‐plane and out‐of‐plane loads. Four solid wall specimens tested to investigate the role of type of interface between the masonry and tie‐columns, such as toothing varying from none to every course. The other four specimens with openings were tested to study the effectiveness of various strengthening options around opening to mitigate their negative influence. In the set of four walls, one wall was infilled frame while the other three were CM walls of different configurations. The experimental results were further used to determine the accuracy of various existing models in predicting the in‐plane response quantities of CM walls. Confined masonry walls maintained structural integrity even when severely damaged and performed much better than infill frames. No significant effect of toothing details was noticed although toothing at every brick course was preferred for better post‐peak response. For perforated walls, provision of vertical elements along with continuous horizontal bands around openings was more effective in improving the overall response. Several empirical and semi‐empirical equations are available to estimate the lateral strength and stiffness of CM walls, but those including the contribution of longitudinal reinforcement in tie‐columns provided better predictions. The available equations along with reduction factors proposed for infills could not provide good estimates of strength and stiffness for perforated CM walls. However, recently proposed relations correlating strength/stiffness with the degree of confinement provided reasonable predictions for all wall specimens. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Training Programme on Major Tectonics and Lithounits in the Indus and Shyok Suture Zones of Ladakh Himalaya — M. Ram Mohan, (NGRI-CSIR,Hyderabad. Email: rammohan@ngri.res.in) and Sita Bora (Kumaun University,Nainital; Email: sitabora@yahoo.com)     

D. Rameshwar Rao  Hakim Rai 《Journal of the Geological Society of India》2011,78(6):600-600

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Training Programme on Major Tectonics and Lithounits in the Indus and Shyok Suture Zones of Ladakh Himalaya — M. Ram Mohan, (NGRI-CSIR, Hyderabad. Email: rammohan@ngri.res.in) and Sita Bora (Kumaun University, Nainital; Email: sitabora@yahoo.com)  相似文献   

Age and geochemistry of the Newania dolomite carbonatites, India: implications for the source of primary carbonatite magma     

Jyotiranjan S. Ray  Kanchan Pande  Rajneesh Bhutani  Anil D. Shukla  Vinai K. Rai  Alok Kumar  Neeraj Awasthi  R. S. Smitha  Dipak K. Panda 《Contributions to Mineralogy and Petrology》2013,166(6):1613-1632

The Newania carbonatite complex of India is one of the few dolomite-dominated carbonatites of the world. Intruding into Archean basement gneisses, the rocks of the complex have undergone limited diversification and are not associated with any alkaline silicate rock. Although the magmatic nature of the complex was generally accepted, its age of emplacement had remained equivocal because of the disturbed nature of radioisotope systems. Many questions about the nature of its mantle source and mode of origin had remained unanswered because of lack of geochemical and isotopic data. Here, we present results of our effort to date the complex using ¹⁴⁷Sm–¹⁴³Nd, ²⁰⁷Pb–²⁰⁶Pb and ⁴⁰Ar–³⁹Ar dating techniques. We also present mineral chemistry, major and trace element geochemistry and Sr–Nd isotopic ratio data for these carbonatites. Our age data reveal that the complex was emplaced at ~1,473 Ma and parts of it were affected by a thermal event at ~904 Ma. The older ²⁰⁷Pb–²⁰⁶Pb ages reported here (~2.4 Ga) and by one earlier study (~2.3 Ga; Schleicher et al. Chem Geol 140:261–273, 1997) are deemed to be a result of heterogeneous incorporation of crustal Pb during the post-emplacement thermal event. The thermal event had little effect on many magmatic signatures of these rocks, such as its dolomite–magnesite–ankerite–Cr-rich magnetite–magnesio-arfvedsonite–pyrochlore assemblage, mantle like δ¹³C and δ¹⁸O and typical carbonatitic trace element patterns. Newania carbonatites show fractional crystallization trend from high-Mg to high-Fe through high-Ca compositions. The least fractionated dolomite carbonatites of the complex possess very high Mg# (≥80) and have similar major element oxide contents as that of primary carbonatite melts experimentally produced from peridotitic sources. In addition, lower rare earth element (and higher Sr) contents than a typical calcio-carbonatite and mantle like Nb/Ta ratios indicate that the primary magma for the complex was a magnesio-carbonatite melt and that it was derived from a carbonate bearing mantle. The Sr–Nd isotopic data suggest that the primary magma originated from a metasomatized lithospheric mantle. Trace element modelling confirms such an inference and suggests that the source was a phlogopite bearing mantle, located within the garnet stability zone.  相似文献   

Geology, petrography and geochemistry of rhyolite-hosted uranium mineralization at Mohar, Shivpuri district, Madhya Pradesh     

Shailendra Kumar  Madhupurna Roy  Pradeep Pandey  C. L. Bhairam  P. S. Parihar 《Journal of the Geological Society of India》2013,81(3):369-376

In the westernmost part of the Bundelkhand Granitoid Complex (BGC), a mesa structure represents a unique outlier, surrounded by brecciated granite and filled with Vindhyan sedimentary rocks locally known as the Dhala Formation near Mohar village of Shivpuri district, Madhya Pradesh. Uranium mineralisation located in the area is mostly associated with rhyolite of peralkaline to peraluminous in nature, that has a high average uranium concentration (30 ppm). The mineralization is in or adjacent to caldera and is hydrothermal vein-type. Radioactivity is mainly due to coffinite with limited radioactivity due to U-Ti complex, uranium adsorbed in clay and labile uranium along fracture. Coffinite occurs in association with pyrite and chalcopyrite or chlorite with presence of fluorite. Features such as chloritisation, clay formation and sulfide mineralisation manifest hydrothermal alteration. Chemical analysis indicates the aluminous nature of the rock and their high K₂O/Na₂O (3.81–12.84) ratios are suggestive of predominance of potash feldspar over sodic. The alteration index varies from 49.88–92.40, which, reflects high intensity of hydrothermal alteration. Chlorite-carbonatepyrite index (CCPI), a measure of the intensity of replacement of sodic feldspars and glass by sericite, chlorite, carbonate, and pyrite associated with hydrothermal alteration proximal to the ore bodies varies from 3.84–49.66. On the basis of core study, geochemistry and mineralogy, it is envisaged that epigenetic hydrothermal solutions were responsible for concentration of uranium as coffinite, radioactive carbonaceous matter and adsorbed uranium phases in rhyolite with sulfide confined to weak planes.  相似文献   

Thermal metamorphism of the Arunachal Himalaya, India: Raman thermometry and thermochronological constraints on the tectono-thermal evolution   总被引：1，自引：0，他引：1  

George Mathew  Sharmistha De Sarkar  Kanchan Pande  Suryendu Dutta  Shakir Ali  Apritam Rai  Shilpa Netrawali 《International Journal of Earth Sciences》2013,102(7):1911-1936

Determination of the peak thermal condition is vital in order to understand tectono-thermal evolution of the Himalayan belt. The Lesser Himalayan Sequence (LHS) in the Western Arunachal Pradesh, being rich in carbonaceous material (CM), facilitates the determination of peak metamorphic temperature based on Raman spectroscopy of carbonaceous material (RSCM). In this study, we have used RSCM method of Beyssac et al. (J Metamorph Geol 20:859–871, 2002a) and Rahl et al. (Earth Planet Sci Lett 240:339–354, 2005) to estimate the thermal history of LHS and Siwalik foreland from the western Arunachal Pradesh. The study indicates that the temperature of 700–800 °C in the Greater Himalayan Sequence (GHS) decreases to 650–700 °C in the main central thrust zone (MCTZ) and decreases further to <200 °C in the Mio-Pliocene sequence of Siwaliks. The work demonstrates greater reliability of Rahl et al.’s (Earth Planet Sci Lett 240:339–354, 2005) RSCM method for temperatures >600 and <340 °C. We show that the higher and lower zones of Bomdila Gneiss (BG) experienced temperature of ~600 °C and exhumed at different stages along the Bomdila Thrust (BT) and Upper Main Boundary Thrust (U.MBT). Pyrolysis analysis of the CM together with the Fission Track ages from upper Siwaliks corroborates the RSCM thermometry estimate of ~240 °C. The results indicate that the Permian sequence north of Lower MBT was deposited at greater depths (>12 km) than the upper Siwalik sediments to its south at depths <8 km before they were exhumed. The ⁴⁰Ar/³⁹Ar ages suggest that the upper zones of Se La evolved ~13–15 Ma. The middle zone exhumed at ~11 Ma and lower zone close to ~8 Ma indicating erosional unroofing of the MCT sheet. The footwall of MCTZ cooled between 6 and 8 Ma. Analyses of P–T path imply that LHS between MCT and U.MBT zone falls within the kyanite stability field with near isobaric condition. At higher structural level, the temperatures increase gradually with P–T conditions in the sillimanite stability field. The near isothermal (700–800 °C) condition in the GHS, isobaric condition in the MCTZ together with T–t path evidence of GHS that experienced relatively longer duration of near peak temperatures and rapid cooling towards MCTZ, compares the evolution of GHS and inverted metamorphic gradient closely to channel flow predictions.  相似文献   

The role of magnetic buoyancy in a Babcock-Leighton type solar dynamo     

Dibyendu Nandy  Arnab Rai Choudhuri 《Journal of Astrophysics and Astronomy》2000,21(3-4):381-385

We study the effects of incorporating magnetic buoyancy in a model of the solar dynamo&amp;#x2014;which draws inspiration from the Babcock-Leighton idea of surface processes generating the poloidal field. We present our main results here.  相似文献