Air-sea fluxes over the global oceans during the FGGE year     

S. Reyes  O. E. Ramírez 《Theoretical and Applied Climatology》1987,38(2):69-78

Summary Vertical fluxes of momentum, sensible and latent heat have been estimated over the surface of the global oceans. A three-dimensional mesh grid 32 longitude points, 17 latitude points and 365 days from December 1, 1978 to November 30, 1979 is used to obtain seasonal and annual mean values of the surface fluxes. The global climatology shows the seasonal variation, the continental influence, the principal ocean currents and the typical middle latitude (30°–50°) and tropical effects (30°S–30°N). The annual mean of latent heat shows greater flux over the subtropical regions (~ 280 W/m²) than in the polar regions (~ 80 W/m²). On the other hand, the annual mean of sensible heat shows greater flux over the polar regions (~ 100 W/m²) than in the tropics (~ 40 W/m²). Time series analyses of the daily estimates of the surface fluxes show greater energy at high frequencies due to the surface effect; however, the low-frequency spectra show relatively high energy at the 30- to 50-day mode, especially for the middle latitude regions. The 30–50 day filtered data for the surface fluxes, presented in time/latitude cross-sections for the middle latitude regions show a westerly wave propagation with wave numberK = 2 and phase speed of the order of 12 degrees/day from June to August over the southern hemisphere at 55°S.

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Zusammenfassung Die vorliegende Studie beschäftigt sich mit der Einschätzung der vertikalen Impuls-Flüsse und der Flüsse von sensibler und latenter Wärme über der gesamten Meeresoberfläche. Ein dreidimensionales Gitter mit 32 × 17 Punkten und Daten von 365 Tagen (von 1. 12. 1978 bis 30. 11. 1979) wird benutzt, um sowohl Jahreszeiten als auch Jahresmittelwerte der Oberflächenflüsse zu erhalten. Die globale Klimatologie zeigt die jahreszeitlichen Schwankungen, den kontinentalen Einfluß, die wichtigsten Meeresströmungen und die typischen Effekte der mittleren Breiten (30°–50°) und der Tropen (30°S–30°N). Das Jahresmittel latenter Wärme weist größere Flüsse über subtropischen Regionen (ca. 280 W/m²) als über polaren Regionen (ca. 80 W/m²) auf, während andererseits das Jahresmittel sensibler Wärme über Polarregionen (ca. 100 W/m²) größere Flüsse als über den Tropen (ca. 40 W/m²) aufweist. Zeitreihen-Analysen der täglichen Schätzwerte von Oberflächenflüssen deuten auf mehr Energie bei hohen Frequenzen aufgrund des Oberflächeneffekts hin; in jedem Fall zeigen die Niederfrequenz-Spektren relativ hohe Energie in den 30 – 50-Tage-Perioden, besonders für mittlere Breiten. Die über einen Zeitraum von 30 – 50 Tagen gesammelten Daten der Oberflächenflüsse dargestellt in Zeit-Breiten-Querschnitten für mittlere Breiten zeigen von Juni bis August über der südlichen Hemisphäre bei 55°S eine Ausbreitung der westlichen Wellen mit der WellenzahlK = 2 und einer Phasengeschwindigkeit im Ausmaß von 12° pro Tag.

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With 7 Figures  相似文献   

Forest site quality assessment by aerial photo-interpretation case study of sal forests     

M. D. Shedha  Suresh Kumar 《Journal of the Indian Society of Remote Sensing》1984,12(2):13-25

93 black & white panchromatic aerial photographs of 1972 on 1:20,000 scale were used for assessing the site quality of Sal forest of part of West Dehradun Forest Division, by both direct and indirect methods. The forests were stratified into 5 height and 5 density classes and according to species composition. For necessary data for the assessment of growing stock, field measurements were made on 54 sample plots of 0.1 hectare each. This provided direct indication of actual productive capacity of a particular site. According to indirect method, ground vegetation was sampled in 54 quadrats of 5m x 5m each and has been classified into statistically sound vegetation groupings by normal association analysis technique. These groups facilitated the standardisation of their photo perameters. The indicator value of the plants in a grouping was used to assess the suitability of the site. This was substantiated by super-imposing growing stock, present at that site. By combination of the direct and indirect methods, sites have been classified into 3 categories i.e., suitable, conditionally suitable and unsuitable. Suggestions have been made for management of conditionally suitable sites and the cause for unsuitability of sites are explored. Hence, interpretation of qualitative attributes of vegetation alongwith the measurements of quantitative parameters on aerial photographs have proved to be useful for site quality assessment.  相似文献   

Apparent velocity and azimuths of short period P-Waves recorded at indian WWSSN stations network     

Avadh Ram  K.N.S. Yadav 《Tectonophysics》1984,104(1-2)

Over 200 earthquakes in the distance range 30°–90° and azimuthal range 0°–360°, recorded at Indian WWSSN stations, have been used in the present study. We have treated the four WWSSN recording stations i.e. New Delhi, Poona, Shillong and Kodai-Kanal, as Super Large Aperture Seismic Array (SLASA) Network with New Delhi being its cross-over point. Short period P-wave data as obtained from these stations have been analysed using a least square technique. Slowness and azimuthal anomalies have been computed for all these events. Relative time residuals have also been calculated. A velocity model has been derived on the basis of the slowness and travel-time data. The results do not indicate presence of any triplication in the travel-time curve. Variations in the relative residuals refer to the tectonic features beneath the recording stations. The P-wave velocity increases continuously in the lower mantle region and there is no indication for the presence of any appreciable velocity gradient.  相似文献   

Ranchi mega lineament and its correlation with geological and geophysical data     

Ashok Kumar  Deepak Srivastava  Sanjay Kumar Srivastava 《Journal of the Indian Society of Remote Sensing》1994,22(1):57-64

Remotely-sensed satellite data of Landsat 5 (TM) and IRS-1A (LISS II) covering parts of central portion of Chotanagapur plateau have been analysed visually to delineate some prominent lineaments in Ranchi district and its adjoining area. One of the most prominent lineament “Ranchi mega lineament? has been analysed in this paper. This lineament is a potential site for base metal mineralisation at some places, and it acts as good groundwater conduit in the region. No earlier attempt to map this entire structural unit as a separate entity is known. Geophysical bouguer gravity anomaly map, lithological and structural maps have some remarkable correlation with this lineament. In the present paper authors have tried to analyse the lineament with respect to its tectonic, mineralisation and groundwater prospects. Resistivity survey carried in close proximity of this lineament at selected sites, indicate that rocks are well fractured at depth. Available lithological and structural map support this lineament as a shear near Purulia (W.B.) and also having base-metal mineralisation potential in this area. Authors opine that existing gravity anomaly map may be further augmented in the light of present study.  相似文献   

An explanation for time dependent variability of the solar dust ring     

Syuzo Isobe  Ambadi Satheesh Kumar 《Astrophysics and Space Science》1993,205(2):297-303

There are several observations showing an enhancement of infrared emission and optical polarization at a distance of 4R , (R is the angular radius of the Sun) implying a ring of dust in near-ecliptic orbit about the Sun; but there is an almost equal number of observations, which do not show any such enhancement. We plotted the observational results for the detection and the non-detection of the circum-solar dust on a diagram for the variation of the sun-spot number with time, and found that its detection and non-detection occurred near the solar minimum and maximum phases, respectively. We present the possibility that this phenomena is caused by an additional process, i.e., the Lorentz force acting on a charged dust particle. Since, at the maximum phase a dust particle in a near-solar region acquires a higher positive potential, and the solar magnetic field is very strong, the Lorentz force becomes dominant and can affect the orbit of the dust particle.  相似文献   

A case for internal migration policy in India     

Ram S 《Population geography : a journal of the Association of Population Geographers of India》1993,15(1-2):65-71

Migration helps to minimize regional, socioeconomic, and cultural disparities, and is considered to be an integral component of the development process. Migration helps to diffuse development, technology, and innovations from more developed areas or cities to rural or less developed areas. Little attention, however, has been paid to migration policy in India. Most studies on migration in India either describe the patterns of migration or analyze reasons for the moves. This paper discusses why migration takes place, what are the consequences of migration, whether India has a migration policy, whether India needs a migration policy, and what type of policy is required. The development and entrenchment of urban slums in India is related to the country's lack of migration policy. A two-pronged policy on migration is thus proposed which would ensure employment opportunities and an improved standard of living in rural areas, while taking into account the planning of cities and city surroundings. Rural areas and small towns need to be provided with more employment opportunities, financial and technological support to process raw materials, infrastructure for agricultural service centers, better education and other facilities to improve local living standards, and the diffusion of industries from big cities to district headquarters and medium-size towns. Commensurate efforts should be made in urban centers to prevent the future development of slums.  相似文献   

Change detection study of islands in Hooghly estuary using multidate satellite images     

K. Vinod Kumar  Arup SPaltt  A. K. Chakrabortt  S. K. Bhan  B. Chowdhury  T. Sanyal 《Journal of the Indian Society of Remote Sensing》1994,22(1):1-7

River estuarine environment constitutes a highly dynamic fluvio-morphological setting where processes of accretion and deposition are active. Hooghly estuary, being one of the largest of estuaries in the east coast of India, needs constant monitoring. Multidate satellite images of IRS-1A L1SS-I and Landsat MSS for 1975–1991 period are studied to detect long term morphological changes in this estuary. The study reveals that the estuarine islands like Sagar, Ghorarmara and Suparbhanga are eroding whereas Lohachara islands has completely eroded off Nayachara island near Haldia due to its shape and size bifurcates the river into two channels. The island as revealed from Satellite images is in accretional phase where the total surface area has increased. The study, therefore, indicates that constant monitoring of spatial and temporal changes in this type of environment would help to understand physical processes.  相似文献   

Influence of southern oscillation and SSTs over Nino-3.4 region on the winter monsoon rainfall over coastal Andhra Pradesh     

O. S. R. U. Bhanu Kumar  C. V. Naidu  S. R. L. Rao 《Journal of Earth System Science》2004,113(3):313-319

An analysis of the mean monthly data of 124 years reveals that the relationship between the Southern Oscillation Index in September and the winter monsoon rainfall (WMR) over Coastal Andhra Pradesh (CAP) is variable and non-stationary. In the recent four decades, however, SOI (Sept) is negatively and significantly correlated with CAP WMR. A similar analysis is performed using 50 years of mean monthly SSTs over Nino-3.4 region in August and September and CAP WMR to detect a possible relationship and there is a striking positive relation between them. In both of the above cases, the September signal is more significant in the recent four decades than for the other months and seasons for probable prediction of CAP WMR. Finally, to examine the influence of SO on the winter monsoon rainfall, a non-parametric test “Mann-Whitney Rank Statistics” test has been applied to the rainfall associated with extreme positive and negative SOI events  相似文献   

Heat and mass transfer of an oscillatory flow with Hall current     

H. L. Agrawal  P. C. Ram  V. Singh 《Astrophysics and Space Science》1983,90(2):445-454

In the first part of these notes new expressions—simpler than any previously obtained—are presented in integral form for the derivatives of the α _n ⁰ -functions (required for an interpretation of the observed light changes of eclipsing variables) with respect to the fractional radiir _{1, 2} and projected separation δ of their centres in terms of the modified Bessel functionsK _{0, 1} (x) of the second kind; and utilized for establishing new asymptotic formulae for the computation of ‘boundary integrals’ of the formJ _?1 ⁰ ,n(μ). In the second part of this paper, by a resort to bi-polar coordinates, we shall establish a new type of expansions for the α _n ⁰ -functions valid for any type of eclipses, and converging faster than the expansions of the cross-correlation integral of the form (1) for α _n ⁰ that have so far been established.  相似文献   

Fluorescence efficiencies of electrons in molecular nitrogen and oxygen gases     

S.P. Khare  A. Kumar 《Planetary and Space Science》1977,25(6):555-562

Fluorescence efficiencies of electrons in a large number of bands of the N₂ First Positive and O₂⁺ First Negative groups lying in the 4900–10,500 Å wavelength range have been investigated theoretically. The variation of transition moment with internuclear distance is taken into consideration. For the First Positive group of N₂ the calculations are carried out at very low pressure as well as at 600 Torr. In general the present values are higher than the experimental values but in most of the cases fair agreement has been obtained. For the O₂⁺ First Negative group no direct experimental data is available. However, the present ratio of the total efficiency in the O₂⁺ First Negative group to the N₂⁺ First Negative group is found to be in good agreement with the experimental intensity ratio.  相似文献