Impact of South China Sea Cold Surges and Typhoon Peipah on Initiating Cyclone Sidr in the Bay of Bengal     

Naresh Krishna Vissa  A. N. V. Satyanarayana  B. Prasad Kumar 《Pure and Applied Geophysics》2013,170(12):2369-2381

In the present study, an attempt was made to understand the role of South China Sea (SCS) convection associated with northerly cold surges and Typhoon Peipah in initiating Cyclone Sidr in the Bay of Bengal (BoB). The variation of air sea fluxes during the entire history of Cyclone Sidr tracking before its landfall over Bangladesh was also studied. The presence of cold surges in the north SCS associated with heavy rainfall episodes has been noticed at the southern Gulf of Tonkin coast prior to the formation of Typhoon Peipah. Subsequently, these surges migrated south, which resulted in intensification of a deep convection on reaching the Vietnamese coast. During the same period in the western Pacific, Typhoon Peipah developed, propagating in the westward direction and entering the SCS. Analysis of geostationary water vapour images, mean sea level pressure, and surface wind maps clearly depicted the transport of convective cloud clusters, moisture, and westward momentum from Typhoon Peipah to the deep convection cells over the SCS. Consequently, the existing deep convection over the Vietnamese coast resulted in a westward direction and entered the Gulf of Thailand and Andaman Sea. The availability of higher latent heat fluxes, warmer sea surface temperatures, and suitable atmospheric conditions over this region favoured the formation of a tropical depression in the Andaman Sea. This depression further intensified in the southeast BoB, resulting in the formation of Cyclone Sidr. NCEP/NCAR wind fields and air-sea fluxes revealed left asymmetry surface winds and higher latent heat flux on the left side of the track during the intensification phase of Sidr.  相似文献   

The 14 April 2012 Koyna Earthquake of M<Subscript>w</Subscript> 4.8: insights into active tectonics of the Koyna region     

D.?ShashidharEmail author  N.?Purnachandra?Rao  D.?Srinagesh  Harsh?Gupta  H.?V.?S.?Satyanarayana  G.?Suresh  A.?Satish 《Journal of Seismology》2013,17(4):1345-1353

The 14 April 2012 earthquake of M_w 4.8 is the best monitored event in the Koyna region, a globally significant site of reservoir triggered seismicity in western India. Hence, investigation of this event assumes great importance, also considering its epicentral location close to that of the 1967 Koyna earthquake of M 6.3, the world’s largest reservoir triggered earthquake. Inversion of P-wave amplitude data along with the first motion polarities at 30 digital seismic stations provides a well-constrained strike-slip type focal mechanism solution, similar to that of the 1967 earthquake. The mechanism is further confirmed by moment tensor inversion of 3-component waveform data recorded at the three nearest broadband stations. The depth distribution of the aftershocks clearly delineates a NNE-SSW trending fault plane dipping about 78° to the WNW and coinciding with the trend of the Donachiwada fault, as well as the left-lateral fault plane of the focal mechanism solution obtained. The precise location, focal mechanism and the seismicity distribution from our dense network indicate that the activity in the Koyna region is mainly controlled by the NNE-SSW trending Donachiwada (D) fault zone rather than the Koyna River Fault Zone (KRFZ) on the west as suggested previously.  相似文献   

Identification of coal seam strata from geophysical logs of borehole using Adaptive Neuro-Fuzzy Inference System     

Satyanarayana Yegireddi  G. Uday Bhaskar 《Journal of Applied Geophysics》2009,67(1):9-13

Different parameters obtained through well-logging geophysical sensors such as SP, resistivity, gamma–gamma, neutron, natural gamma and acoustic, help in identification of strata and estimation of the physical, electrical and acoustical properties of the subsurface lithology. Strong and conspicuous changes in some of the log parameters associated with any particular stratigraphy formation, are function of its composition, physical properties and help in classification. However some substrata show moderate values in respective log parameters and make difficult to identify or assess the type of strata, if we go by the standard variability ranges of any log parameters and visual inspection. The complexity increases further with more number of sensors involved.An attempt is made to identify the type of stratigraphy from borehole geophysical log data using a combined approach of neural networks and fuzzy logic, known as Adaptive Neuro-Fuzzy Inference System. A model is built based on a few data sets (geophysical logs) of known stratigraphy of in coal areas of Kothagudem, Godavari basin and further the network model is used as test model to infer the lithology of a borehole from their geophysical logs, not used in simulation. The results are very encouraging and the model is able to decipher even thin cola seams and other strata from borehole geophysical logs. The model can be further modified to assess the physical properties of the strata, if the corresponding ground truth is made available for simulation.  相似文献   

LRS Bianchi type-II dark energy model in a scalar–tensor theory of gravitation     

R. L. Naidu  B. Satyanarayana  D. R. K. Reddy 《Astrophysics and Space Science》2012,338(2):333-336

A locally rotationally symmetric Bianchi type-II (LRS B-II) space-time with variable equation of state (EoS) parameter and constant deceleration parameter have been investigated in the scalar-tensor theory proposed by Saez and Ballester (Phys. Lett. A 113:467, 1986). The scalar-tensor field equations have been solved by applying variation law for generalized Hubble’s parameter given by Bermann (Nuovo Cimento 74:182, 1983). The physical and kinematical properties of the model are also discussed.  相似文献   

Five dimensional dark energy model in a scalar-tensor theory of gravitation     

D. R. K. Reddy  B. Satyanarayana  R. L. Naidu 《Astrophysics and Space Science》2012,339(2):401-404

A five dimensional Kaluza-Klein dark energy model with variable equation of state (EoS) parameter and a constant deceleration parameter is presented in Saez and Ballester (Phys. Lett. A 113:467, 1986) scalar-tensor theory of gravitation. Some physical and kinematical properties of the model are also discussed.  相似文献   

Response of upper ocean and impact of barrier layer on Sidr cyclone induced sea surface cooling     

Naresh Krishna Vissa  A. N. V. Satyanarayana  B. Prasad Kumar 《Ocean Science Journal》2013,48(3):279-288

In the present study an attempt has been made to investigate the impact of salinity stratification on the SST during the tropical cyclone (TC) passage. In this context, a severe post monsoon cyclone, Sidr, (Category 4) that developed over the south-eastern Bay of Bengal (BoB) during 11–16 November, 2007 was chosen as a case study. Pre-existence of a thick barrier layer (BL), temperature inversions and a higher effective oceanic layer for cyclogenesis (EOLC) were noticed along the path of the Sidr cyclone. The analysis of available Argo floats along the Sidr cyclone track also revealed less cooling during as well as after its passage as was reported from satellite derived SST. The role of BL on Sidr induced sea surface cooling was investigated using a diagnostic mixed layer model. Model results also depict the reduced sea surface cooling during the passage of Sidr. This is attributed to the presence of BL which results in the inhibition of the entrainment of cool thermocline water into the shallow mixed layer. Climatological as well as in situ observations of tropical cyclone heat potential (TCHP) and EOLC shows that the Sidr cyclone propagated towards the regions of higher EOLC.  相似文献   

Effect of varied atmospheric stability on sea surface drag in shallow seas and its impact on wind-wave growth     

R. Rajesh Kumar  B. Prasad Kumar  A. N. V. Satyanarayana  D. Bala Subrahamanyam  A. D. Rao  S. K. Dube 《Natural Hazards》2009,49(2):213-224

This work reports an efficient bulk formulation of sea surface drag that incorporates effect of dynamic stability under varied atmospheric forcing. The proposed formulation exhibits a polynomial dependence of wind speed on air–sea temperature difference based on statistical analysis. Quality checked meteorological and oceanographic data from four shallow water buoys located off Korean seas having measurements at an interval of every 1 h were used for this study. The analyses of in situ records for this region suggest stability ranging from highly stable to very unstable conditions. Importance of this proposed formulation is better reflected during unstable condition where other popular bulk formulations fail. In addition, importance and impact of such a study on wind-wave growth using the state-of-art wave model was also investigated. Finally, we advocate a new drag formulation, which accounts for varied atmospheric stability and suggest that this should be considered as an essential pre-requisite for ocean modeling studies.  相似文献   

High resolution seismic evidence for Ghaggar lineament and paleo-Saraswathi River     

Gidugu Himakantha  D. Mysaiah  P. Pavan Kishore  K. Satish Kumar  K. Dhanam  P. Swamy  T Seshunarayana  H. V. S. Satyanarayana 《Arabian Journal of Geosciences》2017,10(9):216

Geophysical data are needed to correlate the lineaments at the surface to the structural mapping of underlying bedrock. High resolution seismic survey is one of the most suitable geophysical methods for mapping of shallow features. In this study, 2D high resolution seismic reflection survey (HRSS) has been carried out across the Ghaggar, a seasonal river in Haryana, India. The survey is carried out for a profile distance of 10 km across the lineament along the course of Ghaggar River. Ground checks along the river have shown sediments containing alternate layers of alluvium deposits with yellowish silty clay and fine-grained gray sand of variable thickness. Several structural disturbances along the profile are identified. During the quantitative analyses, the results exhibit disturbances in the reflector representing the bedrock. Also, regional gravity data study does not report any major tectonic feature indicating the absence of seismicity associated with the lineament. The present study resulted in that (a) the1.5-km wide zone of disturbance is more likely to be a fracture rather than a major fault across the basement in the depth and (b) the meandering drainage pattern of the Ghaggar River which indicates that it is a basement-controlled lineament.  相似文献   

Temporal dynamics of CO2 fluxes and profiles over a Central European city     

R. Vogt  A. Christen  M. W. Rotach  M. Roth  A. N. V. Satyanarayana 《Theoretical and Applied Climatology》2006,84(1-3):117-126

Summary In Summer 2002 eddy covariance flux measurements of CO₂ were performed over a dense urban surface. The month-long measurements were carried out in the framework of the Basel Urban Boundary Layer Experiment (BUBBLE). Two Li7500 open path analysers were installed at z/z_H = 1.0 and 2.2 above a street canyon with z_H the average building height of 14.6 m and z the height above street level. Additionally, profiles of CO₂ concentration were sampled at 10 heights from street level up to 2 z_H. The minimum and maximum of the average diurnal course of CO₂ concentration at 2 z_H were 362 and 423 ppmv in late afternoon and early morning, respectively. Daytime CO₂ concentrations were not correlated to local sources, e.g. the minimum occurred together with the maximum in traffic load. During night-time CO₂ is in general accumulated, except when inversion development is suppressed by frontal passages. CO₂ concentrations were always decreasing with height and correspondingly, the fluxes – on average – always directed upward. At z/z_H = 2.2 low values of about 3 μmol m⁻² s⁻¹ were measured during the second half of the night. During daytime average values reached up to 14 μmol m⁻² s⁻¹. The CO₂ fluxes are well correlated with the traffic load, with their maxima occurring together in late afternoon. Daytime minimum CO₂ concentrations fell below regional background values. Besides vertical mixing and entrainment, it is suggested that this is also due to advection of rural air with reduced CO₂ concentration. Comparison with other urban observations shows a large range of differences among urban sites in terms of both CO₂ fluxes and concentrations. Present affiliation: Swiss Federal Office for Meteorology and Climatology, MeteoSwiss, Zürich, Switzerland  相似文献   

Land Surface Layer Characteristics During Monsoon at a Tropical Station     

D. V. Viswanadham  A. N. V. Satyanarayana  M. K. Srivastava 《Pure and Applied Geophysics》1997,150(1):129-142

—The atmospheric surface layer over land may behave differently in the tropics, particu larly during the monsoon. A preliminary attempt is made to observe the behavior of surface layer characteristics such as fluxes of momentum, sensible heat and latent heat, friction velocity, friction temperature, M-O length scale, Richardson number and Bowen’s ratio over Kharagpur (22°20′N, 87°18′E), a typical moist tropical station. The diurnal and day-to-day variations have been studied. It is observed that during the active phase of the monsoon the sensible heat flux and Bowen’s ratio are low. The diurnal variation is apparent for most parameters. Mostly near neutral conditions are observed.  相似文献