Influence of different land-surface processes on Indian summer monsoon circulation     

A. P. Singh  U. C. Mohanty  P. Sinha  M. Mandal 《Natural Hazards》2007,42(2):423-438

The impact of different land-surface parameterisation schemes for the simulation of monsoon circulation during a normal monsoon year over India has been analysed. For this purpose, three land-surface parameterisation schemes, the NoaH, the Multi-layer soil model and the Pleim-Xiu were tested using the latest version of the regional model (MM5) of the Pennsylvania State University (PSU)/National Center for Atmospheric Research (NCAR) over the Indian summer monsoon region. With respect to different land-surface parameterisation schemes, latent and sensible heat fluxes and rainfall were estimated over the Indian region. The sensitivity of some monsoon features, such as Somali jet, tropical easterly jet and mean sea level pressure, is discussed. Although some features of the Indian summer monsoon, such as wind and mean sea level pressure, were fairly well-simulated by all three schemes, many differences were seen in the simulation of the typical characteristics of the Indian summer monsoon. It was noticed from the results that the features of the Indian summer monsoon, such as strength of the low-level westerly jet, the cross-equatorial flow and the tropical easterly jet were better simulated by NoaH compared with verification analysis than other land-surface schemes. It was also observed that the distribution of precipitation over India during the peak period of monsoon (July) was better represented with the use of the NoaH scheme than by other schemes.

U. C. MohantyEmail:

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Spectroscopic and microstructural studies of ruby gemstones of Sinapalli,Odisha     

Jatin Kumar Sinha  Pratima Kumari Mishra 《Journal of the Geological Society of India》2015,86(6):657-662

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Spatial frequencies associated with the latitudinal structures of ionospheric currents seen by CHAMP satellite     

Neethal Thomas  Geeta Vichare  A. K. Sinha 《Astrophysics and Space Science》2016,361(7):205

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Oxygen isotope analysis of multiple,single ostracod valves as a proxy for combined variability in seasonal temperature and lake water oxygen isotopes   总被引：1，自引：0，他引：1  

Yama Dixit  David A. Hodell  Rajiv Sinha  Cameron A. Petrie 《Journal of Paleolimnology》2015,53(1):35-45

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Generation of waves in Boussinesq models using a source function method   总被引：4，自引：0，他引：4  

Ge Wei  James T. Kirby  Amar Sinha 《Coastal Engineering》1999,36(4):1027

A method for generating waves in Boussinesq-type wave models is described. The method employs a source term added to the governing equations, either in the form of a mass source in the continuity equation or an applied pressure forcing in the momentum equations. Assuming linearity, we derive a transfer function which relates source amplitude to surface wave characteristics. We then test the model for generation of desired incident waves, including regular and random waves, for both one and two dimensions. We also compare some model results with analytical solution and available experiment data.  相似文献   

Parameter identification of torsionally coupled shear buildings from earthquake response records     

Ganesh Hegde  Ravi Sinha 《地震工程与结构动力学》2008,37(11):1313-1331

This paper presents an efficient procedure to determine the natural frequencies, modal damping ratios and mode shapes for torsionally coupled shear buildings using earthquake response records. It is shown that the responses recorded at the top and first floor levels are sufficient to identify the dominant modal properties of a multistoried torsionally coupled shear building with uniform mass and constant eccentricity even when the input excitation is not known. The procedure applies eigenrealization algorithm to generate the state‐space model of the structure using the cross‐correlations among the measured responses. The dynamic characteristics of the structure are determined from the state‐space realization matrices. Since the mode shapes are obtained only at the instrumented floor (top and first floors) levels, a new mode shape interpolation technique has been proposed to estimate the mode shape coefficients at the remaining floor levels. The application of the procedure has been demonstrated through a numerical experiment on an eight‐storied torsionally coupled shear building subjected to earthquake base excitation. The results show that the proposed parameter identification technique is capable of identifying dominant modal parameters and responses even with significant noise contamination of the response records. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Effects of Climate Change on Rice Production in the Tropical Humid Climate of Kerala, India     

S. A. Saseendran  K. K. Singh  L. S. Rathore  S. V. Singh  S. K. Sinha 《Climatic change》2000,44(4):495-514

The CERES-Rice v3. crop simulation model, calibrated and validated for its suitability to simulate rice production in the tropical humid climate Kerala State of India, is used for analysing the effect of climate change on rice productivity in the state. The plausible climate change scenario for the Indian subcontinent as expected by the middle of the next century, taking into account the projected emissions of greenhouse gases and sulphate aerosols, in a coupled atmosphere-ocean model experiment performed at Deutsches Klimarechenzentrum, Germany, is adopted for the study. The adopted scenario represented an increase in monsoon seasonal mean surface temperature of the order of about 1.5°C, and an increase in rainfall of the order of 2 mm per day, over the state of Kerala in the decade 2040–2049 with respect to the 1980s. The IPCC Business-as-usual scenario projection of plant usable concentration of CO₂ about 460 PPM by the middle of the next century are also used in the crop model simulation. On an average over the state with the climate change scenario studied, the rice maturity period is projected to shorten by 8% and yield increase by 12%. When temperature elevations only are taken into consideration, the crop simulations show a decrease of 8% in crop maturity period and 6% in yield. This shows that the increase in yield due to fertilisation effect of elevated CO₂ and increased rainfall over the state as projected in the climate change scenario nearly makes up for the negative impact on rice yield due to temperature rise. The sensitivity experiments of the rice model to CO₂ concentration changes indicated that over the state, an increase in CO₂ concentration leads to yield increase due to its fertilisation effect and also enhance the water use efficiency of the paddy. The temperature sensitivity experiments have shown that for a positive change in temperature up to 5°C, there is a continuous decline in the yield. For every one degree increment the decline in yield is about 6%. Also, in another experiment it is observed that the physiological effect of ambient CO₂ at 425 ppm concentration compensated for the yield losses due to increase in temperature up to 2°C. Rainfall sensitivity experiments have shown that increase in rice yield due to increase in rainfall above the observed values is near exponential. But decrease in rainfall results in yield loss at a constant rate of about 8% per 2 mm/day, up to about 16 mm/day.  相似文献   

Channel morphodynamics and sediment budget of the Lower Ganga River using a hydrogeomorphological approach     

Rajiv Sinha  Shobhit Singh  Kanchan Mishra  Somil Swarnkar 《地球表面变化过程与地形》2023,48(1):14-33

The Ganga River is one of the largest river systems in the world that has built extensive alluvial plains in northern India. The stretch of the Lower Ganga River is vulnerable to siltation because of: (a) the naturally low slope in the alluvial stretch; (b) the confluence of several highly sediment-charged rivers such as the Ghaghra, Gandak, and Kosi; and (c) the reduction in non-monsoon flows because of upstream abstractions of both surface and groundwater. Additionally, the Farakka barrage has impacted the morphology of the Ganga River significantly, both upstream and downstream of the barrage. Large-scale siltation in several reaches has reduced the channel capacity, leading to catastrophic floods in this region even at low discharges. This work has utilized historical remote sensing data and UAV surveys to reconstruct channel morphodynamics and compute sediment volumes accumulated in the channel belt along the Lower Ganga River between Buxar and Farakka. The work was carried out by dividing the total length of the river into four continuous stretches: (a) Buxar–Gandhighat (GW1, 160 km); (b) Gandhighat–Hathidah (GW2, 106 km); (c) Hathidah–Azmabad (GW3, 182 km); and (d) Azmabad–Farakka (GW4, 132 km). We document that major ‘hotspots’ of siltation have developed in several reaches of the Lower Ganga during the last four to five decades. Sediment budgeting using planform maps provides estimates of ‘extractable’ volumes of sediment in GW1, GW2, GW3, and GW4 as 656 ± 48, 706 ± 52, 876 ± 71, and 200 ± 85 Mm³, respectively. These estimates are considerably lower than those computed from the hydrological approach using observed suspended sediment load data, which assumes uniform sedimentation between two stations. Further, our approach provides reach-scale hotspots of aggradation and estimates of extractable sediment volumes, and this can be very useful for river managers to develop a strategic sediment management plan for the given stretch of the Ganga River.  相似文献   

Estimation of Sea Surface Temperature (SST) Using Marine Seismic Data     

Satish Kumar Sinha  Pawan Dewangan  Kalachand Sain 《Pure and Applied Geophysics》2016,173(4):1305-1316

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Structural imaging of Mesozoic sediments of Kachchh,India, and their hydrocarbon prospects     

Dhananjai Pandey  Satish Singh  Martin Sinha  Lucy MacGregor 《Marine and Petroleum Geology》2009

Travel-time modelling of first and second arrivals has been used to produce P-wave velocity models of the shallow sub-surface structure of Kachchh, India, using new wide-angle reflection/refraction profiles. Results obtained from the 2-D tomographic modelling have also been corroborated with magnetotelluric and borehole data within the proximity of these profiles. Based on multiple geophysical data, a composite sub-surface model is presented in this article. The prominent features of the model include the presence of more than 3 km thick Mesozoic sediments residing above the Precambrian basement. Its correlation with available lithological knowledge shows that the Mesozoic rocks have been deposited from early Triassic to late Cretaceous until the eruption of the Deccan Flood basalts at the Cretaceous-Tertiary boundary. The new results suggest that the Mesozoic rocks of Kachchh can be sub-divided in two major parts which correspond to late and early Mesozoic deposits respectively. The sub-surface models successfully demarcate the regional variations in the basaltic layer across the region and show maximum thickness of 1.2 km. The modelling results also exhibit that the Precambrian basement in this region varies between 4 and 6 km depth. The new data provide a much clearer picture than was hitherto available of the entire sedimentary succession in the basins that underlie the Kachchh region. They show a significant variability in thickness of the various sedimentary layers, and in particular illustrate a marked topographic irregularity at the base of the sedimentary succession.  相似文献