Impacts of recent El Niño Modoki on dry/wet conditions in the Pacific rim during boreal summer     

Hengyi Weng  Karumuri Ashok  Swadhin K. Behera  Suryachandra A. Rao  Toshio Yamagata 《Climate Dynamics》2007,29(2-3):113-129

Present work uses 1979–2005 monthly observational data to study the impacts of El Niño Modoki on dry/wet conditions in the Pacific rim during boreal summer. The El Niño Modoki phenomenon is characterized by the anomalously warm central equatorial Pacific flanked by anomalously cool regions in both west and east. Such zonal SST gradients result in anomalous two-cell Walker Circulation over the tropical Pacific, with a wet region in the central Pacific. There are two mid-tropospheric wave trains passing over the extratropical and subtropical North Pacific. They contain a positive phase of a Pacific-Japan pattern in the northwestern Pacific, and a positive phase of a summertime Pacific-North American pattern in the northeastern Pacific/North America region. The western North Pacific summer monsoon is enhanced, while the East Asian summer monsoon is weakened. In the South Pacific, there is a basin-wide low in the mid-latitude with enhanced Australian high and the eastern South Pacific subtropical high. Such an atmospheric circulation pattern favors a dry rim surrounding the wet central tropical Pacific. The El Niño Modoki and its climate impacts are very different from those of El Niño. Possible geographical regions for dry/wet conditions influenced by El Niño Modoki and El Niño are compared. The two phenomena also have very different temporal features. El Niño Modoki has a large decadal background while El Niño is predominated by interannual variability. Mixing-up the two different phenomena may increase the difficulty in understanding their mechanisms, climate impacts, and uncertainty in their predictions.  相似文献   

Characterization of channel planform features and sinuosity indices in parts of Yamuna River flood plain using remote sensing and GIS techniques     

Armugha Khan  Liaqat A. K. Rao  Ali P. Yunus  Himanshu Govil 《Arabian Journal of Geosciences》2018,11(17):525

River planform features and sinuosity are widely acknowledged as important geomorphological indices that control the channel hydraulics and stream power which determines the flow velocity and sediment supply to downstream reaches. Despite their significance, there has been little study about these indices in mighty Yamuna River for understanding the topographic control and hydraulic regime. This paper investigates the channel planform features and sinuosity by employing topographic map, digital elevation model (DEM), and satellite imageries to elucidate the morphological, sedimentological, and hydrological characteristics of the channel. Based on sinuosity index (varies between 1.02 and 1.41), the river segments are categorized into straight (segments 1, 3, 4, 5, 6), sinuous (segments 2, 7, 8, 9, and 11), and meandering (segment 10). The parameters analyzed to find out the influencing factors on sinuosity indicate geomorphological and anthropologic control in their development. Tectonic control of sinuosity in the studied stretch is ruled out as it is flowing through an alluvial plain with low rate of discharge.  相似文献   

Flood Inundation Hazard Modelling Using CCHE2D Hydrodynamic Model and Geospatial Data for Embankment Breaching Scenario of Brahmaputra River in Assam     

Sagar S. Salunkhe  S. S. Rao  I. Prabu  V. Raghu Venkataraman  Y. V. N. Krishna Murthy  Chintamani Sadolikar  Supriya Deshpande 《Journal of the Indian Society of Remote Sensing》2018,46(6):915-925

In many flood prone river basins, water inundates vast areas of land causing loss of life and heavy damage to the dwellings in flood plains. It also impacts agricultural productivity and cause severe economic losses. One of the reasons for flooding in plains of Brahmaputra valley in north east India is embankment breaching. In this study, an attempt was made for probabilistic flood hazard modelling of July 2008 embankment breaching scenario of Brahmaputra river at Matmara village, Lakhimpur district in Assam, based on various numerical simulations with the help of Center for Computational Hydro science and Engineering hydro-dynamic model. The methodology was applied over 2146 km² flood prone area. Data inputs in the study include: Advanced Spaceborne Thermal Emission and Reflection Radiometer Digital Elevation Model, Pre-flood and Post flood satellite images of Landsat Enhanced Thematic Mapper Plus (ETM+) and other ancillary data. The simulation was carried out for various discharge levels based on flood frequency analysis. The result of the model includes spatial variations of inundated water depth and water velocity. The results were validated by comparing it with the post-flood ETM+ data and flood situation status report of National Informatics Centre. Flood hazard maps were prepared by carrying out a spatial analysis of simulated inundation depth and velocity. It was seen that the majority of flooded area fell into the very high and high categories. This information can be used to plan appropriate cost effective flood mitigation schemes.  相似文献   

Seasonal and inter-annual variability of atmosphere CO<Subscript>2</Subscript> based on NOAA Carbon Tracker analysis and satellite observations     

M. Krishnapriya  A. Bhuvana Chandra  Rabindra K. Nayak  N. R. Patel  P. V. N. Rao  V. K. Dadhwal 《Journal of the Indian Society of Remote Sensing》2018,46(2):309-320

A study on seasonal and inter-annual variability of the atmospheric CO₂ is carried out based on National Oceanic and Atmospheric Administration Carbon Tracker (NOAACT) re-analysis and satellite measurements of mid-troposphere CO₂ by Atmosphere Infrared Sounder on board NASA’s Aqua and lower troposphere CO₂ by Greenhouse-gas Observing Satellite. Seasonal and non-seasonal components of each time series were extracted by means of least square based harmonic analysis procedure. The data of surface CO₂ fluxes used in the NOAACT are also analyzed to examine its relationship with the atmosphere CO₂ variability at different time scales. There exists good consistency between NOAACT analysis and satellite observations in their respective seasonal harmonics and climatology. Surface layer CO₂ exhibits large climatological mean over the regions of major anthropogenic sources together with strong seasonal cycle over the humid and cold climatic terrestrial regions especially over the northern hemisphere. Existence of high coherency with the different components of the surface fluxes shows that surface layer atmosphere CO₂ seasonality is primarily contributed from the terrestrial ecosystem exchanges and secondarily by anthropogenic and oceanic exchanges. The mid-troposphere CO₂ exhibits large values associated with climatology and amplitudes of semi-annual and annual cycles over the northern extra tropics and Polar Regions along with a gradual decreasing trend from northern to southern hemisphere. Inter-annual variability of atmospheric CO₂ in the NOAACT in some extent is consistent with the satellite observations. Large scale circulation patterns, its fluctuations associated with ENSO events and large scale ecosystem disturbances have significant influence on the inter-annual variability.  相似文献   

Analysis of Deformation of Adjacent Buried Pipeline Under Rockfall Impact Load     

Rao  Pingping  Wu  Zhilin  Cui  Jifei 《Geotechnical and Geological Engineering》2022,40(3):1463-1474

Geotechnical and Geological Engineering - The current research on the deformation of buried pipeline under rockfall impact load is generally based on the analysis of the pipeline cross-sectional...  相似文献   

Impact of the moisture and land surface processes on the sustenance of the cyclonic storm Yemyin over land using the WRF-ARW model     

Nellipudi  Nanaji Rao  Ramakrishna  S. S. V. S.  Podeti  Srinivasa Rao  Rao  B. Ravi Srinivasa  Yesubabu  V.  Rao  V. Brahmananda 《Natural Hazards》2022,114(1):495-519

Natural Hazards - In this study, an attempt is made to analyze the sensitivity of land surface process and the associated moisture budget characteristics of the cyclonic storm Yemyin (2007), which...  相似文献   

Numerical investigation of the stability of landslide-affected slopes in Kerala,India, under extreme rainfall event     

Das  Tanmoy  Rao  Vansittee Dilli  Choudhury  Deepankar 《Natural Hazards》2022,114(1):751-785

Natural Hazards - This study examines the stability and failure mechanisms of two landslide-affected slopes in Kerala, India, after an extreme rainfall event. The landslide was triggered by an...  相似文献   

白云凹陷中深层有利储层特征及其分布预测          下载免费PDF全文

谢晓军  熊连桥  白海强  黄饶  李飞跃  唐武  陈莹 《地球科学》2022,47(5):1635-1651

白云凹陷中深层未探明油气资源潜力巨大,储层总体为低孔低渗储层,为了识别海域中深层有利储层的特征,寻找能用于指导有利储层宏观分布预测的主控因素,并对有利储层空间分布进行预测,对白云凹陷5A构造开展了研究.通过储层岩石学、储层物性特征及建设性成岩作用分析等微观方面与储层相带识别、厚层砂体发育的前积复合体预测、砂体与孔隙度地震反演及裂缝分布识别等宏观方面研究,对中深层有利储层“甜点”特征、宏观可识别的主控因素及空间分布规律开展分析.认为,白云5A构造辫状河三角洲平原与前缘中的分流河道和水下分流河道厚层中?粗砂岩发育次生溶孔和微裂缝,可作为储层“甜点”;反映沉积微相的砂体厚度及反映建设性成岩作用的裂缝是宏观可以识别的储层“甜点”主控因素,可通过地震外部形态的“上拱”、内幕结构的叠置及微地貌的低洼3个特征在地震上识别厚层砂体发育的前积复合体;综合厚层砂体识别、砂体及孔隙度预测、裂缝分布识别三方面成果,认为白云5A构造中深层C块东部为储层“甜点”发育区.   相似文献   

B. P. Radhakrishna – A Lone Crusader     

M. S. Rao 《Journal of the Geological Society of India》2018,91(1):5-8

Pyrite containing appreciable content of cobalt (up to 5.61 wt%) and minor amounts of nickel (up to 0.70 wt%) is being reported from electron microprobe studies in a lamprophyre dyke from the Sidhi complex, Mahakoshal belt, Central India. However, cobalt and nickel are conspicuously absent from the associated chalcopyrite reflecting that in a pyrite-chalcopyrite association these elements are preferentially sequestered in pyrite. The microprobe analysis of pyrite grains reveal that their Fe content is variable (40.62 to 46.02 wt%) and reciprocally related to cobalt and nickel concentrations implying the presence of latter as solid solution in the structure of pyrite. The cobalt contents of the pyrite are comparable to those (up to 3.21 wt%) reported from the cobaltbearing pyrites of the Kalyadi copper deposits of Dharwar craton of southern India. Co:Ni (16.05 average) in the studied pyrite appears to be more consistent with a magmatic, rather than a hydrothermal, origin. However, further studies are in progess. This study highlights that besides gold and diamond, lamprophyres are also important carriers of cobalt when available in the magmatic system.  相似文献   

Spatial Potential Analysis of Earthquakes in the Western Himalayas Using b-value and Thrust Association     

Ramesh Pudi  Priyom Roy  Tapas R. Martha  K. Vinod Kumar  P. Rama Rao 《Journal of the Geological Society of India》2018,91(6):664-670

In this study, we have analysed the spatial variation of b-values (from frequency-magnitude distribution (FMD)) in the western Himalayas as an indicator to demarcate the potential zones of earthquake occurrences. This is done under the acceptance of interpretation that decrease of b-values is correlated with a stress increase in the epicentral region of an approaching earthquake event. In addition to this, the spatial association of the earthquake epicenters with the major thrusts in the region using weights of evidence method, to identify potential zones of earthquake occurrences have also been analysed. Both analyses were carried out using a historical earthquake (M_w> 4) database of the1900-2015 period. Finally, based on the spatial variation of b-values and ‘contrasts’ derived from weights of evidence method (thrust associations), the derived map information was geospatially combined to prepare a “spatial earthquake potential” map of the western Himalayas. This map demarcates the western Himalayas into 3 zones - high, medium and low potential for future earthquake occurrences.  相似文献