Interannual variability of onset of the summer monsoon over India and its prediction     

P. V. S. Raju  U. C. Mohanty  R. Bhatla 《Natural Hazards》2007,42(2):287-300

In this article, the interannual variability of certain dynamic and thermodynamic characteristics of various sectors in the Asian summer monsoon domain was examined during the onset phase over the south Indian peninsula (Kerala Coast). Daily average (0000 and 1200 UTC) reanalysis data sets of the National Centre for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR) for the period 1948–1999 were used. Based on 52 years onset date of the Indian summer monsoon, we categorized the pre-onset, onset, and post-onset periods (each an average of 5 days) to investigate the interannual variability of significant budget terms over the Arabian Sea, Bay of Bengal, and the Indian peninsula. A higher difference was noticed in low-level kinetic energy (850 hPa) and the vertically integrated generation of kinetic energy over the Arabian Sea from the pre-onset, onset, and post-onset periods. Also, significant changes were noticed in the net tropospheric moisture and diabatic heating over the Arabian Sea and Indian peninsula from the pre-onset to the post-onset period. It appears that attaining the magnitude of 40 m² s⁻² and then a sharp rise in kinetic energy at 850 hPa is an appropriate time to declare the onset of the summer monsoon over India. In addition to a sufficient level of net tropospheric moisture (40 mm), a minimum strength of low-level flow is needed to trigger convective activity over the Arabian Sea and the Bay of Bengal. An attempt was also made to develop a location-specific prediction of onset dates of the summer monsoon over India based on energetics and basic meteorological parameters using multivariate statistical techniques. The regression technique was developed with the data of May and June for 42 years (1948–1989) and validated with 10 years NCEP reanalysis from 1990 to 1999. It was found that the predicted onset dates from the regression model are fairly in agreement with the observed onset dates obtained from the Indian Meteorology Department.  相似文献   

Land use changes in udumbanchola taluk, idukki district—Kerala: An analysis with the application of remote sensing data     

K. Raju  R. Anil Kumar 《Journal of the Indian Society of Remote Sensing》2006,34(2):161-169

Udumbanchola Taluk, located in the fragile zone of Western Ghats in the Idukki District of Kerala has undergone severe land use changes in the past century. The changing land use scenario of Udumbanchola Taluk was assessed using remote sensing technique. The historic land use map was derived from topographic maps of Survey of India, surveyed in 1910 and published during 1912–14. The land use map of 1997 was generated through the visual interpretation of IRS—1 C LISSIII images supported by ground truths and was observed that the original land use system was highly modified. The comparative study shows that the settlement areas that occupied hardly 0.73 % in 1910 were increased to 30.57 % in 1997 by transferring forest lands, grassland and cardamom plantations. Due to the depletion of natural vegetation and grassland system by the establishment of houses, cash crops and infrastructure facilities, combined with the absence of sufficient land management measures in the side slopes resulted severe land degradation and the present status of degraded lands is about 14.12 % of the total geographical area. It is also observed that the prevailing agro-climatic conditions favorable for the sustenance of sensitive crops like cardamom has undergone changes mainly due to the impact of large-scale land use modifications.  相似文献   

Multifrequency spectra of solar brightness temperature derived from eclipse observations     

S. K. Alurkar  R. V. Bhonsle  S. S. Degaonkar  O. P. N. Calla  G. Raju 《Journal of Astrophysics and Astronomy》1983,4(4):289-293

Changes in solar radio-brightness temperature were derived at 2.8,19.3 and 22.2 GHz from the observations of radio flux during the total eclipse of 1980 February 16. High-resolution MEM spectra of the brightness temperature fluctuations at the three frequencies showed periodicities ranging from 3.5 min to 128 min. Between 3.5 min and 14.6 min there are several periodicities of comparable significance common to the three operating frequencies. If the corresponding variations in brightness temperature are assumed to result from spatial variations in the solar radio emission, the observed periodicities imply scale sizes in the range 76000 km to 320000 km.  相似文献   

Hydrogeomorphological and groundwater prospects of the Pageru river basin by using remote sensing data   总被引：2，自引：0，他引：2  

P. Sree Devi  S. Srinivasulu  K. Kesava Raju 《Environmental Geology》2001,40(9):1088-1094

Hydrogeomorphology and lineament studies have been completed by using satellite data for the Pageru river basin, Cuddapah district, Andhra Pradesh, India through visual interpretation of IRS-1B-LISS II FCC (57J/6, J/7, J/10 and J/11) on a 1:50,000 scale. The area has been visually interpreted to delineate various hydrogeomorphic units and lineaments for the development of groundwater. From these studies, various geomorphic units were classified as favourable, moderately favourable and poor zones of groundwater. The integration of geomorphology and lineament studies reveal that shallow groundwater occurrence is controlled by geomorphological characteristics whereas faults/fractures control the yield of groundwater at intermediate depths.  相似文献   

Deccan Trap and the geologic framework of the Cambay basin     

A. T. R. Raju  A. N. Chaube  L. R. Chowdhary 《Bulletin of Volcanology》1971,35(3):521-538

The subsurface information gathered during exploration for oil and gas in the Cambay basin shows it as a deep graben with 5 km or more of Tertiary and Quaternary sediments resting on the Deccan Trap floor. The Trap floor of this graben extends from Lat. 24° N to about Lat. 19° N and possibly further south. The basin is divisible into separate morphotectonic blocks as a result of block differentiation in the Trap basement, reflected in the structural attitudes of the overlying sediments. This differentiation is believed to have originated in the Paleocene. The dominant structural grain of the area to south of the Narmada river is ENE-WSW with block faulting in the Traps along the older Satpura trend. North of the Narmada river, the trend is longitudinal upto the Meshwa river while further north the trends veer to a NNW-SSE alignment. These latter trends, in the greater part of the Cambay basin, were impressed early during its subsidence and are the result of reactivation along the old Dharwarian trends in post-Delhi times. Maximum thickness of the Traps penetrated so far is near Mechsana and Cambay where more than 1000 meters thickness has been drilled through. The drilling and gravity-magnetic evidence shows the thickness of Deccan Traps in this trough to be of the order of 2.5 km and points to the possibility of active subsidence of Cambay basin, concomitant with the outpouring of the basaltic lavas. The age of the Traps in the Cambay basin, as evidenced by the available data, is Upper Crealaceous. The influence of the structural grain of the basaltic floor on the overlying sedimentary sequence is evidenced during all the stages in the evolution of the Cambay Tertiary basin. Conglomerates, wackes and reddish brown clays of exclusive Trap derivation predominate in the sedimentary section in the initial stage of the basin evolution during Paleocene. General absence of well developed terrigenous reservoirs on a regional scale in the Paleogene section is due to predominance of Trap terrain as the provenance of clastic detritus, contributing essentially argillaceous matter.  相似文献   

Evaluation of simulated IRS-1C WiFS data for concurrent monitoring of command areas at disaggregated level     

S. Jonna  K. Abdul Hakeem  C. S. Murthy  P. V. Raju  S. T. Chari 《Journal of the Indian Society of Remote Sensing》1995,23(4):185-194

Data of Wide Field Sensor (WiFS) to go onboard Indian Remote Sensing Satellite, IRS-1C, in December 1995, is simulated mainly from IRS IB LISS I data of Bhadra command area, Karnataka (India) during 1993–94 summer season, to evaluate its capability in concurrent monitoring of irrigated crops at disaggregated level Crop area, crop-growth profiles of homogeneous crops like paddy, as obtained from both simulated WiFS data and LISS I data are very close for almost all the distributary commands of Bhadra project Though non-paddy-crop groups could also be classified satisfactorily, the Workability with small-extent-individual crops like groundnut, garden and sugarcane is found to be less due to coarse resolution of WiFS data and hence the individual crops could not be separated out. This study proves the potential of WiFS in concurrent monitoring of fairly-large-extent irrigated crops at distributary level. The basic feasibility of WiFS had been established in an earlier work at broad level and this study demonstrates the feasibility of information extraction at distributary command level from WiFS data.  相似文献   

Fracture pattern and electrical resistivity studies for groundwater exploration   总被引：1，自引：0，他引：1  

N. Janardhana Raju  T. V. K. Reddy 《Environmental Geology》1998,34(2-3):175-182

 The occurrence, movement and control of groundwater, particularly in hard-rock areas, are governed by different factors such as topography, lithology, structures like fractures, faults and nature of weathering. An attempt is made in the present study to investigate the extent of the influence of structures such as fractures and thereby delineate the nature of subsurface lithology with the help of an electrical resistivity method. For this study, the Upper Gunjanaeru River basin, Cuddapah district Andhra Pradesh was chosen to determine groundwater potentials. In order to understand the significance of the fracture pattern, geological, hydrogeomorphological and lineament maps were prepared based on the field data and also from the LANDSAT TM imagery. Further, electrical resistivity surveys were conducted to determine the subsurface lithology and also to confirm the studies of LANDSAT imagery. The isoresistivity contour map has been prepared based on the 45 VES conducted to determine the resistivity variations in the study area. The isoresistivity contours obtained were found to conform to the structural trends obtained by geological studies and also confirm the relationship between the structure and secondary porosity present in the rocks. The lineaments in the area have two preferred directions. One set is a NE-SW direction (N 30°–70° E; S 30°–70° W) and another is a NW-SE direction (N 0°–30° W; S 0°–30° E and N 60°–80° W; S 60°–80° E). The water-table contour map shows that the direction of groundwater flow is south to north. Received: 3 March 1997 · Accepted: 17 June 1997  相似文献   

Assessment of chemical and microbial contamination in groundwater through leaching of sewage waste in Delhi,India     

Ashwani Kumar  Anuj Ranjan  Khushbu Gulati  Shalini Thakur  Tanu Jindal 《Environmental Earth Sciences》2016,75(3):275

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Markov random field-based method for super-resolution mapping of forest encroachment from remotely sensed ASTER image     

L.K. Tiwari  S.K. Sinha  S. Saran  V.A. Tolpekin  P.L.N. Raju 《国际地球制图》2016,31(4):428-445

Forest encroachment (FE) is a problem in Andaman and Nicobar Islands (ANI) in India for environment and planning. Small gaps created in the forest slowly expand its periphery disturbing the biodiversity. Therefore, intrusion of poachers, slash and burn and other factors causing FE must be carefully detected and monitored. Remote sensing offers a great opportunity to accomplish this task because of its synoptic view. Conventional classification methods with remotely sensed images are problematic because of small size of FE and mixed landcover composition. This study presents an application of super-resolution mapping (SRM) based on Markov random field for detection of FE using ASTER (15 m) images. The SRM results were validated using multispectral IRS LISS-IV (5.8 m) image. Non-contiguous FE patches of various sizes and shapes are characterized using the spatial contextual information. The novelty of this approach lies in the identification and separability of small FE pockets which could not be achieved with pixel-based maximum likelihood classifier (MLC). The SRM parameters were optimized and found comparable to previous studies. Classification accuracy obtained with SRM at scale factor 3 is κ = 0.62 that is superior to accuracy of MLC (κ = 0.51). SRM is a promising tool for detection and monitoring of FE at Rutland Island in ANI, India.  相似文献   

Hydrogeochemical evaluation of groundwater quality and seasonal variation in East Bokaro coalfield region,Jharkhand     

Mukesh Kumar Mahato  Prasoon Kumar Singh  Ashwani Kumar Tiwari 《Journal of the Geological Society of India》2016,88(2):173-184

Groundwater samples collected from the East Bokaro coalfield of Jharkhand state, India during the dry and rainy seasons of the year 2012. Samples were analyzed for the assessment of groundwater quality in the study area. The results of the chemical analysis indicate that the pH values were found alkaline in nature during both the season. The major cations in groundwater was in the order of Na⁺>Ca²⁺>Mg²⁺>K⁺ during the dry season while Ca²⁺>Na⁺>Mg²⁺>K⁺ during the rainy season. The abundance of the major anions was of HCO₃^->SO₄^2->Cl^->NO₃^->F^- did not change on the seasonal basis. The average NO₃^-concentration was exceeded the desirable limit for drinking water as per Indian standard in the rainy season. Silicate weathering was inferred to be a dominant process, controlling the groundwater chemistry in both seasons, with lesser contributions by carbonate weathering and ion exchange. Leaching of salts from the unsaturated zone also has a major impact on groundwater quality during the rainy season. The water quality data indicate that groundwater is generally suitable for irrigation. However, higher salinity and residual sodium carbonate values at some sites may limit groundwater use and therefore an adequate drainage and water management plan for the study area is required.  相似文献