Observational perspective of SST changes during life cycle of tropical cyclones over Bay of Bengal     

Pothapakula  Praveen Kumar  Osuri  Krishna K.  Pattanayak  Sujata  Mohanty  U. C.  Sil  Sourav  Nadimpalli  Raghu 《Natural Hazards》2017,88(3):1769-1787

Natural Hazards - Sea surface temperature (SST) plays a significant role in tropical cyclone (TC) formation and intensity evolution, while at the same time, TC induces SST changes during its life...  相似文献   

Dynamics of sea-ice biogeochemistry in the coastal Antarctica during transition from summer to winter     

Suhas Shetye  Babula Jena  Rahul Mohan 《地学前缘(英文版)》2017,8(3):507-516

The seasonality of carbon dioxide partial pressure(pCO_2).air-sea CO_2 fluxes and associated environmental parameters were investigated in the Antarctic coastal waters.The in-situ survey was carried out from the austral summer till the onset of winter[January 2012,February 2010 and March 2009) in the Enderby Basin.Rapid decrease in pCO_2 was evident under the sea-ice cover in January,when both water column and sea-ice algal activity resulted in the removal of nutrients and dissolved inorganic carbon(DIC) and increase in pH.The major highlight of this study is the shift in the dominant biogeochemical factors from summer to early winter.Nutrient limitation(low Si/N),sea-ice cover,low photosynthetically active radiation(PAR),deep mixed layer and high upwelling velocity contributed towards higher pCO_2during March(early winter).CO_2 fluxes suggest that the Enderby Basin acts as a strong CO_2 sink during January(-81 mmol m~2 d~(-1)),however it acts as a weak sink of CO_2 with-2.4 and-1.7 mmol m~(-2) d~(-1)during February and March,respectively.The present work,concludes that sea ice plays a dual role towards climate change,by decreasing sea surface PCO_2 in summer and enhancing in early winter.Our observations emphasize the need to address seasonal sea-ice driven CO_2 flux dynamics in assessing Antarctic contributions to the global oceanic CO_2 budget.  相似文献   

Effect of traditional management practices on woody species composition and structure in montane subtropical forests of Meghalaya,Northeast India     

Aabid Hussain Mir  Krishna Upadhaya 《山地科学学报》2017,14(8):1500-1512

In Meghalaya, northeast India, the local people have the tradition of managing forest resources since early ages. The management practice varies and there are forests with high degree of protection, where no extraction (sacred forests) is allowed. There are also forests with moderate- level of protection and -extraction (reserved forests) as well as forests with low level of protection and open extraction (village forests). The present study was conducted to understand the impact of this traditional management system on the level of human disturbance, and on community composition and structure of the forests in Khasi hills of Meghalaya. The result revealed that disturbance index was low, whereas species richness, density and basal cover were significantly high in forests with high degree of protection (sacred forest) than those with low protection (reserved and village forest). Majority of endemic and threatened plant species were restricted to sacred forests as compared to the other forest types. Though these practices have ensured the sustainable use of forest resources by the local people but due to increased human- pressure and -disturbances, more effective conservation strategies need to be undertaken. Therefore, providing alternatives for fuel Received: 28 July 2016 Revised: 1 October 2016 Accepted: 15 December 2016 wood to local people, environmental education, encouraging afforestation and developmental activities involving local communities are recommended.  相似文献   

Two-dimensional interpretation of gravity anomalies over sedimentary basins with an exponential decrease of density contrast with depth     

D. Bhaskaa Rao  C. P. V. N. J. Mohan Rao 《Journal of Earth System Science》1999,108(2):99-106

The decrease of density contrast with depth in sedimentary basins is approximated by an exponential function. The anomaly equation, in frequency domain, of a prismatic model with an exponential density function is derived. The method has been extended to derive the Fourier transforms of the gravity anomalies of the sedimentary basin, wherein the basin is viewed as vertical prisms placed in juxtaposition. The gravity anomalies of the sedimentary basin are obtained by taking the inverse Fourier transforms. Filon’s method has been extended for calculating accurate inverse Fourier transforms. The accuracy of the method has been tested using a synthetic example. A combination of space and frequency domain methods have been developed for inversion of gravity anomalies over the sedimentary basin. The method has been applied to interpret one synthetic profile and one field profile over the Godavari basin. The method developed in this paper to calculate the inverse Fourier transforms yields continuous spectrum with accurate values. The maximum depth deduced from the gravity anomalies is of the same order as the depth encountered to the basement at the Aswaraopeta borewell.  相似文献   

The role of stratification and initial conditions on the propagation and decay of near-inertial waves on a $$\beta $$ -plane     

Peddada  Siva Heramb  Chalamalla  Vamsi Krishna 《Ocean Dynamics》2023,73(7):387-406

Ocean Dynamics - In this study, we model the evolution of near-inertial waves (NIWs) under the $$\beta $$ -effect by imposing initial zonal velocity in the mixed layer. We consider various...  相似文献   

Evaluating the impact of climate change in threshold values of thermodynamic indices during pre-monsoon thunderstorm season over Eastern India     

Sahu  Rajesh Kumar  Dadich  Jiteshwar  Tyagi  Bhishma  Vissa  Naresh Krishna  Singh  Jyotsna 《Natural Hazards》2020,102(3):1541-1569

Natural Hazards - The present study analyses thermodynamic indices variation over three sites of eastern Indian region: Bhubaneswar, Kolkata and Ranchi, associated with pre-monsoon thunderstorms...  相似文献   

Toxic Trace Metals in the Surface Water Sources of Jia–Bharali river basin,North Brahmaputra Plain,India—A Hydrochemical Elucidation     

Nayan J. Khound  Phukon  Parag  Bhattacharyya  Krishna G. 《Water Resources》2019,46(1):117-127

Water Resources - Surface water samples from thirty five sources in the Jia Bharali river basin in north Brahmaputra plain, North East India were analyzed for ten toxic trace elements namely As,...  相似文献   

Structural information derived from ambient noise tomography over a hydrocarbon-producing region in the Cachar fold belt,lower Assam,northeast India     

Bharath Shekar  Gollapally Mohan  Sunil Kumar Singh 《Geophysical Prospecting》2023,71(1):140-162

Ambient noise tomography is a powerful tool that has found increasing application in reservoir analysis and imaging. The Cachar fold belt in lower Assam, northeast India encompasses several wells under active hydrocarbon production, along with several dry wells. To overcome the lack of active seismic data over the entire fold belt, a passive seismic study was carried out to image the concealed three-dimensional sub-surface structures. The data were recorded from February to November 2011 by a network of 65 wideband seismometers spanning an area of about 40 × 60 km². The data are crosscorrelated in the 2–5 s band, followed by phase-weighted stacking to estimate noise correlation functions with surface wave signatures. The traveltimes picked from the frequency-time analysis are utilized in a tomographic inversion for Rayleigh wave group velocities. The group velocity anomalies have a lateral resolution of ~ 3.5 × 5.5 km² and variations of up to $\pm 20\%$ for each period. The group velocities are in turn inverted for S-wave velocity distribution as a function of depth. The three-dimensional S-wave velocity tomograms reveal the tight anticlines and broad synclines, with high- and low-velocity zones corresponding to structural highs and lows, respectively. The structural interpretation is supported for the part of the region with producing wells and covered by active seismic data, wherein the post-stack time migrated seismic section shows anticlinal and synclinal features similar to those obtained from ambient noise tomography. The structures revealed by ambient noise tomography can help identify zones of interest to be targeted by active seismic surveys in the Cachar fold belt.  相似文献