Remote sensing approach for watershed based resources management in the Sikkim Himalaya: A case study     

Akhouri Pramod Krishna 《Journal of the Indian Society of Remote Sensing》1996,24(2):71-83

Integrated and environmentally sustainable development strategies have become inevitable for micro-level planning these days. The usefulness of remotely sensed data from earth resource satellites for watershed management is discussed for an eastern Himalayan watershed covering 39.09 km² area. The biophysical conditions were assessed based on field experience. The SPOT HRV-I MLA and PLA scenes were interpreted for land use/cover categories and associated characteristics. These parameters were found to be significant towards evolving the management priorities for development of agriculture, soil conservation, afforestation and rain water harvesting structures in ecologically fragile Himalayan region. The remote sensing inputs were important in deriving the relevant details faster and precisely.  相似文献   

The value ofC efor the Arabian Sea during summer monsoon     

A. Suryachandra Rao  Y. Sadhuram  V. V. Gopala Krishna 《Journal of Earth System Science》1995,104(4):607-611

We estimate, from the moisture budget the bulk aerodynamic coefficient for latent heat flux (C _e) during the monsoon season over the central Arabian Sea. The average value ofC _eunder active monsoon conditions was found to be 2.25 × 10⁻³ which is nearly 60% higher than those previously used.  相似文献   

Finite strain theory of love waves     

Krishna De 《Pure and Applied Geophysics》1970,80(1):114-123

Summary The propagation of Love waves is discussed on the basis of finite strain theory. The primary Love wave is found to be associated with a secondary Rayleigh wave and a tertiary Love wave. Numerical calculations are presented for two values of the wave-velocity; the results show that the theory of Love waves based on infinitesimal strain, is not applicable to short period waves.  相似文献   

Effects of E-region electric fields on F-region parameters at the magnetic equator     

K.Sen Gupta  B.V.Krishna Murthy 《Planetary and Space Science》1973,21(12):2227-2232

The effects of E-region electric fields on F-region parameters like height of constant electron density contours (h_N) and semi-thickness, at an equatorial station, Trivandrum, are investigated. The E-region east-west electric field (E_y) has been deduced using the horizontal magnetic field values from the ground magnetograms. It is found that the semi-thickness parameter and h_N follow closely the E-region electric field (E_y) variations in the forenoon and noon periods. In the afternoon, it is shown that there is close association between h_N and E_y, when the electric field variations are large. On a day-to-day basis also, h_N and the E-region electric field show very good correlation in the forenoon and noon hours. It is also shown that higher levels are affected more than the lower levels in the F-region by E_y.  相似文献   

Nature of the 400-km Discontinuity in the Earth's Mantle     

K. L. Kaila  V. G. Krishna 《Geophysical Journal International》1976,46(1):185-188

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Aerosol optical depth, physical properties and radiative forcing over the Arabian Sea     

S. K. Satheesh  K. Krishna Moorthy  Y. J. Kaufman  T. Takemura 《Meteorology and Atmospheric Physics》2006,91(1-4):45-62

Summary The Arabian Sea region (4° N–20° N to 50° E–78° E) has a unique weather pattern on account of the Indian monsoon and the associated winds that reverse direction seasonally. The aerosol data, collected using ship-borne and island platforms (for 8 years from 1995 to 2002) along with MODIS (onboard TERRA satellite) data (from 2000 to 2003) have been used to evolve a comprehensive characterisation of the spatial and temporal variation in the physical, chemical, and radiative properties of aerosols over the Arabian Sea. The aerosol optical depth (AOD) was found to increase with latitude between the equator and 12° N. Over the northern Arabian Sea (regions lying north of 12° N), AODs do not show significant latitudinal variations; the average aerosol optical depth for this region was 0.29±0.12 during winter monsoon season (WMS; November to March) and 0.47±0.14 during summer monsoon season (SMS; April/May to September). The corresponding Angstrom exponents were 0.7±0.12 and 0.3±0.08, respectively. The low values of the exponent during SMS indicate the dominance of large aerosols (mainly dust particles >1 μm). The latitudinal gradient in AOD in the southern Arabian Sea is larger during SMS compared to WMS. The size distribution of aerosols shows two well-defined modes, one in the accumulation size regime and the other in the coarse size regime. During WMS, a third mode (nucleation) also appears in the sub micron range below ∼0.1 μm. The single scattering albedo does not show significant seasonal variations (remains within ∼0.93 to 0.98 through out the year). During WMS (SMS), top of the atmosphere diurnally averaged aerosol forcing remains around −6.1 (−14.3)W m⁻² over the northern Arabian Sea up to around 12° N and decreases southwards till it attains a value of −3.8 (−3.4)W m⁻² at the equator. The surface forcing remains around −16.2(−15.2)W m⁻² over the northern Arabian Sea up to 12° N and decreases southwards to a value of −5.5 (−3.5)W m⁻² at the equator. Over the north Arabian Sea, instantaneous forcing (flux change) at the surface can be as high as −50 W m⁻². The instantaneous forcing decreases with latitude in the southern Arabian Sea at a rate of ∼3 W m⁻²deg⁻¹.  相似文献   

Hydrogen photoproduction ofA. Variabilis incorporated in a photobioreactor     

Jian-guo  Liu  Hall  David O.  Rao  Krishna K.  Tsygankov  Anatoly A.  Sveshnikov  Dmitry A. 《中国海洋湖沼学报》1998,16(1):118-126

H₂ photoproduction and nitrogenase activities in two strains ofAnabaena variabilis marked wild type ATCC 29413 and mutant PK84 exposed to thermal stress (temperature higher than the normal incubation temperature of 30°C) were studied. Cultures of both strains collected from any interval of logarithmic growth phase exhibited high H₂ photoproduction and nitrogenase activities when exposed to limited time heat shock during the assay process. In contrast, the algal H₂ photoproduction rate of both strains fluctuated with long term thermal stress caused by increasing the growth temperature from 30°C to 36°C.

The changes of nitrogenase (the key H₂ photobiosynthetic enzyme) activities in the mutant PK84 showed variation tendency similar to that of H₂ photoproduction during exposure to thermal stress, indicating that fluctuation of H₂ photoproduction in the mutant was mainly due to the variation of nitrogenase activities. A temporary maximal H₂ photoproduction in the mutant PK84 (wild type ATCC29413) was observed when cells grew at 36°C for 14 (6) days. However, the responses of nitrogenase activities in the wild type to thermal stress were not completely similar to those in the mutant in spite of similar variations of H₂ photoproduction in both strains. The data obtained in these studies suggested that the activities of other enzymes (in the wild strain) involved in H₂ photoproduction were affected by thermal stress since H₂ photoproduction maximized or dropped to 0 without variation tendency similar to that of nitrogenase activities.

Furthermore, an enhancement of H₂ photoproduction speed of the mutant strain cultured in a 4.4 L laboratory photobioreactor was also observed when it was subjected to short time continuous charge of argon, and temperature rise.

All these results indicated that high temperature plays an important role in the photo-autotrophic H₂ photoproduction, and that long term thermal stress is unfavourable for net H₂ photoproduction in both strains ofA. variabilis though short-time heat shock is conducive to H₂ photoproduction.

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The structure of the natural stratosphere and the impact of chlorofluoromethanes on the ozone layer investigated in a 2-D time dependent model     

R. Krishna Rao Vupputuri 《Pure and Applied Geophysics》1978,117(3):448-485

two-dimensional time dependent model of the stratosphere incorporating the major interactions between radiative-photochemical and dynamical processes is described. The main prognostic equations considered are the thermodynamic equation and the general conservation equation for the minor chemical constituents representing the odd oxygen (O _x =O+('D)+O₃), odd hydrogen (HO _x =HO+HO₂), N₂O, odd nitrogen (NO _x =NO+NO₂+HNO₃), CF₂Cl₂, CFCl₃ and odd chlorine (Cl _x =Cl+ClO+HCl). The zonal wind and mean meridional circulations are determined diagnostically by the integration of the thermal wind equation and the stream function equation in the meridional plane espectively. The large scale eddy processes are parameterized in terms of zonal mean quantities using the generalized diffusion formulation on a sloping surface. The radiative heating and cooling and the hotochemical sources and sinks are incorporated in a form which allows for the major interactions among the minor trace constituents, temperature and mean circulation.Two integrations consisting of natural stratosphere and a stratosphere contaminated by the chlorofluoromethanes through lower boundary fluxes are carried out for 23 model years by changing the declination of the sun every day and using 6-hour time step. The model simulations of temperature, mean circulation, ozone, HO _x , N₂O and NO _x in the meridional plane for the normal stratosphere, show satisfactory agreement with the available observations. Based on the results of second integration it is found that the injection of chlorofluoromethanes in the atmosphere at the estimated current production rates can lead to significant changes in the meridional distribution of ozone, temperature and NO _x in the middle and upper stratosphere. The results also indicate that the percentage total ozone depletion increases from tropics to high latitudes and from summer to winter high latitudes. Also discussed are the results of additional experiments incorporating the reaction of HO₂ with NO and the reactions involving ClNO₃.  相似文献   

Seaward dipping reflectors along the SW continental margin of India: Evidence for volcanic passive margin     

K. K. Ajay  A. K. Chaubey  K. S. Krishna  D. Gopala Rao  D. Sar 《Journal of Earth System Science》2010,119(6):803-813

Multi-channel seismic reflection profiles across the southwest continental margin of India (SWCMI) show presence of westerly dipping seismic reflectors beneath sedimentary strata along the western flank of the Laccadive Ridge — northernmost part of the Chagos-Laccadive Ridge system. Velocity structure, seismic character, 2D gravity model and geographic locations of the dipping reflectors suggest that these reflectors are volcanic in origin, which are interpreted as Seaward Dipping Reflectors (SDRs).  相似文献   

Distribution of arsenic and mercury in subtropical coastal beachrock,Gulf of Mannar,India   总被引：1，自引：0，他引：1  

J Dajkumar Sahayam  N Chandrasekar  S Krishna Kumar  G Victor Rajamanickam 《Journal of Earth System Science》2010,119(1):129-135

An assessment of coastal pollution was made on the basis of trace element concentrations (arsenic — As, mercury — Hg) in the Gulf of Mannar. The beachrock samples were collected along the coastal tracts between Rameswaram and Kanyakumari. The samples were dried and digested to determine the As and Hg using atomic absorption spectrophotometer (AAS-air-acetylene and nitrous oxide method). The As and Hg accumulation status of the beachrock was assessed using geo-accumulation index values (I _geo). The accumulation of As and Hg in the beachrock ranges from 2.75 to 20.72 μg g⁻¹ and from 0.06 to 0.31 μg g⁻¹, respectively. The As and Hg concentrations in the beachrocks are compared with crustal average values and average of other region sediments. The possible source of the contamination is from atmospheric deposition and anthropogenic activities.  相似文献