Horizontal moisture distribution from TIROS-N high resolution infrared sounder (HIRS)     

Vijay K. Agarwal  Ashajayanthi Loganathan 《Journal of Earth System Science》1981,90(3):291-304

A direct linear relationship between water vapour content of lower, middle and upper-middle troposphere respectively with the radiances for 8.3, 7.3 and 6.7 μm spectral observations has been attempted. From the atmospheric simulations such a relationship is found to exist with a good degree of correlation and is seen to be quite insensitive to temperature changes. Such an approach is used to interpret the water vapour imageries obtained from TIROS-N sounder through construction of detailed water vapour distribution maps.  相似文献   

Static deformation of two welded half-spaces due to dip-slip faulting     

Sunita Rani  Sarva Jit Singh 《Journal of Earth System Science》1992,101(3):269-282

Closed-form expressions for the displacements and stresses at any point of either of two elastic half-spaces in welded contact caused by a dip-slip line source obtained earlier are integrated analytically to derive the elastic residual field due to a long dip-slip fault of finite width. The results are valid for an arbitrary dip of the fault. The variation of the displacement field with the distance from the fault as well as with the distance from the interface is studied numerically. It is found that the displacement field is heavily dependent on the dip angle. Contour maps showing the residual elastic field in the two half-spaces caused by a vertical dip-slip fault located in one of the half-spaces are also obtained.  相似文献   

An application of complex demodulation technique to geomagnetic data and conductivity anomaly studies     

A. K. Agarwal  B. P. Singh  N. Nityananda 《Journal of Earth System Science》1980,89(1):67-77

The method of complex demodulation has been used here to compute the amplitude and phase of a signal present in a geomagnetic series using, Banks’ method. It is found that the results are quite accurate when four or more continuous cycles of the signal of interest are present. The same limitations have also been observed when band-pass filters are used to isolate a signal. The information on phase is always correct. It is concluded that complex demodulation will give correct results for periodic variations like 11-year, 27-day, Sq or pulsations; but will give small values of amplitude for signals like sudden impulses or bays. The latter is not a limitation in conductivity studies where ratios likeZ/H, Z/D orH/D are mostly used in calculations. It has been shown that even with the records of one magnetic storm the cause of anomalies can be accurately identified which otherwise would need a large number of events.  相似文献   

Observations of the atmospheric surface layer parameters over a semi arid region during the solar eclipse of August 11th, 1999     

Praveena Krishnan  P. K. Kunhikrishnan  S. Muraleedharan Nair  Sudha Ravindran  Radhika Ramachandran  D. B. Subrahamanyam  M. Venkata Ramana 《Journal of Earth System Science》2004,113(3):353-363

This paper discusses the observations of the Atmospheric Surface Layer (ASL) parameters during the solar eclipse of August 11th, 1999. Intensive surface layer experiments were conducted at Ahmedabad (23‡21′N, 72‡36′E), the western part of India, which was close to the totality path. This rare event provided by nature is utilised to document the surface layer effects during the eclipse period using measurements of high frequency fluctuations of temperature, tri-axial wind components as well as mean parameters such as temperature, humidity, wind speed and subsoil temperature. Analysis showed that during the eclipse period, the turbulence parameters were affected leading to the suppression of the turbulence process, the main dynamic process in the atmospheric boundary layer, while the mean parameters showed variations within the natural variability of the observational period. The spectra of the wind components and temperature indicated decrease in spectral power by one order in magnitude during the eclipse period. The rate of dissipation of turbulent kinetic energy is found to decrease by more than one order during the eclipse period. The stability parameter showed a change from unstable to stable condition during the period of eclipse and back to unstable condition by the end of eclipse  相似文献   

Coefficient sets for one dimensional gravity operations using filter theory     

B. N. P. Agarwal  Tarkeshwar Lal 《Pure and Applied Geophysics》1971,85(1):5-11

Summary Between three at a time of the four quantities ellipticity of the niveau-ellipsoid of the earth, gravity flattening, gravity gradient flattening and ellipticity of the isogravitational surface touching the niveau-ellipsoid at the equator there are functional relations in form of determinant equations.

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Zusammenfassung Zwischen jeweils drei der vier Grössen Abplattung des Niveauellipsoids der Erde, Schwereabplattung, Schweregradientabplattung und Abplattung der das Niveauellipsoid im Äquator berührenden Fläche konstanter Schwerebeschleunigung werden Funktionalbeziehungen in Form von Determinantengleichungen aufgestellt.

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Direct gravity interpretation of sedimentary basin using digital computer — Part II     

B. N. P. Agarwal 《Pure and Applied Geophysics》1971,86(1):13-17

Summary An algorithm, suitable for digital computer application, has been developed for rapid gravity interpretation of sedimentary basin. A discrete linear variable density contrast pattern over the constant density contrast has been preferred to obtain the structural configuration of the basin. The present algorithm, with slight modification, can be used for calculation of isostatic root increment below the mountain. An interpretation of the structure of Godavari Valley, India has been made using this algorithm.  相似文献   

Crustal deformation due to non-uniform slip along a long fault     

Sarva Jit Singh  Mukesh Punia  Sunita Rani 《Geophysical Journal International》1994,118(2):411-427

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Observations of Pc5 micropulsation-related electric field oscillations in the equatorial ionosphere     

C. A. Reddy  Sudha Ravindran  K. S. Viswanathan  B. V. Krishna Murthy  D. R. K. Rao  T. Araki 《Annales Geophysicae》1994,12(6):565-573

A 54.95-MHz coherent backscatter radar, an ionosonde and the magnetometer located at Trivandrum in India (8.5○N, 77○E, 0.5○N dip angle) recorded large-amplitude ionospheric fluctuations and magnetic field fluctuations associated with a Pc5 micropulsation event, which occurred during an intense magnetic storm on 24 March 1991 (A_p=161). Simultaneous 100-nT-level fluctuations are also observed in the H-component at Brorfelde, Denmark (55.6○N gm) and at Narsarsuaq, Greenland (70.6○N gm). Our study of the above observations shows that the E-W electric field fluctuations in the E- and F-regions and the magnetic field fluctuations at Thumba are dominated by a near-sinusoidal oscillation of 10 min during 1730–1900 IST (1200-1330 UT), the amplitude of the electric field oscillation in the equatorial electrojet (EEJ) is 0.1-0.25 mV m⁻¹ and it increases with height, while it is about 1.0 mV m⁻¹ in the F-region, the ground-level H-component oscillation can be accounted for by the ionospheric current oscillation generated by the observed electric field oscillation in the EEJ and the H-component oscillations at Trivandrum and Brorfelde are in phase with each other. The observations are interpreted in terms of a compressional cavity mode resonance in the inner magnetosphere and the associated ionospheric electric field penetrating from high latitudes to the magnetic equator.  相似文献   

Characterisation of respirable dust exposure of different category of workers in Jharia Coalfields     

Jai Krishna Pandey  Deepa Agarwal  Sanjoy Gorain  Rajnish Kumar Dubey  Manoj Kumar Vishwakarma  Kamlesh Kumar Mishra  Asim Kumar Pal 《Arabian Journal of Geosciences》2017,10(7):183

This paper presents dust exposure study of 69 workers engaged in 11 categories of jobs over seven coalmines of Jharia Coalfields. Dust samples were analysed for dust concentration, maximum exposure limit (MEL), free silica and other minerals present, and particle size and shape. Study reveals that workers engaged in vicinity of coal/rock cutting operation, are exposed to higher dust concentration (50% samples exceeding MEL), and contain more fine particles (d ₅₀ < 5 μm) with sharp edges. Samples exceeding MEL are classified as high-risk category which needs special attention for taking preventive and protective measure like use of personal protective equipments, job rotation and reduction in dust generation through engineering control using appropriate technology of dust suppression and dust extraction as per their applicability. The study also suggests presence of kaolinite and asbestos along with quartz which make the dust more harmful in nature necessitating further investigation and careful control measures.  相似文献   

Topology of Rayleigh–Bénard convection and magnetoconvection in plane layer     

Hari Ponnamma Rani  Jozef Brestenský 《地球物理与天体物理流体动力学》2019,113(1-2):208-221

ABSTRACT

The present study aims to link the dynamics of geophysical fluid flows with their vortical structures in physical space and to study the transition of these structures due to the control parameters. The simulations are carried in a rectangular box filled with liquid gallium for three different cases, namely, Rayleigh–Bénard convection (RBC), magnetoconvection (MC) and rotating magnetoconvection (RMC). The physical setup and material properties are similar to those considered by Aurnou and Olson in their experimental work. The simulated results are validated with theoretical results of Chandrasekhar and experimental results of Aurnou and Olson. The results are also topologically verified with the help of Euler number given by Ma and Wang. For RBC, the onset is obtained at Ra greater than 1708 and at this Ra, the symmetric rolls are orientated in/along a horizontal axis. As the value of Ra increases further, the width of the horizontal rolls starts to amplify. It is observed that these two-dimensional rolls are nothing but the cross-sections of three-dimensional (3D) cylindrical rolls with wave structures. When the vertically imposed magnetic field is added to RBC, the onset of convection is delayed due to the effect of Lorentz force on the thermal buoyancy force. The presence of 3D rectangular structures is highlighted and analysed. When the magnetically influenced rectangular box rotates about vertical axis at low rotation rates in magnetoconvection model, the onset of convection gets further delayed by magnetic field, which is in general agreement with the theoretical predictions. The critical Ra increases linearly with magnetic field intensity. Coherent thermal oscillations are detected near the onset of convection, at moderate rotation rates.  相似文献