018197   Ramteke R S;Ghosh N;Rao C S;Satpute M S (Central Water and Power Research Station, , Khadakwasla, Pune-24) : Seismic refraction survey of the Yeshwantsagar Reservoir embankments for augmentation of water supply to Indore, M.P.. J Geophys 1999, 20(3), 117-21.

Seismic refraction survey was carried out on the downstream side of the embankment of Yeshwantsagar reservoir near Indore. M.P., to delineate the bedrock profile and to detect weak zones, if any, for founding the structure of new spillway. Four Continuous seismic profiles of length varying from 105 m to 405 m were taken. The results of the seismic survey revealed a three layer earth section. Seismic wave velocity through the overburden range from 500 m/sec to 800 m/sec and it comprises mainly soft clay. The second layer, comprising stiff clay/coarse sand with gravel has compressional wave velocity ranging from 1400 to 2500 m/sec. The third layer, being compact basalt, has a compressional wave velocity ranging from 4000 m/sec to 5200 m/sec indicating good quality of rock. Rock having compressional wave velocity less than 4000 m/sec was considered to be weak, weathered or fractured. The depth to the bedrock range between 6.7 m to 17.3 m and was corroborative with borehole data.

018196   Rama Varma Raja M K;Asnani G C;Salvekar P S; Jain A R;Narayana rao D;Venkoba Rao S;Kishore P;Hareesh M (NO, Indian Institute of Tropical Meteorology, Dr Homi Bhabha Road, Pune-411 008) : Layered clouds in the Indian monsoon region. Proc Indian Acad Sci-Earth Planet Sci 1999, 108(4), 287-95.

Contrary to the prevalent belief that tropical region is characterized by convective clouds rather than by layer clouds, suggested that deep convective clouds occur on meso-scale, but layer clouds occur on large synoptic-scale with a relatively small region of deep convective clouds. Sustenance of deep convective clouds is inhibited by the presence of inertio-gravity waves, which have alternating layers of upward and downward motion in the vertical. Also shown that inertio-gravity waves generate regions of relatively strong horizontal velocity, vertically separated by layers of relatively weak horizontal velocity. Layers of strong horizontal velocity are created by inertio-gravity wave system through convergence of vertical flux of horizontal momontum. Horizontal convergence/divergence of moisture flux is generated by inertio-gravity waves, giving rise to vertically alternating layers of highlow humidity, and visible or sub-visible clouds. Layers of high humidity become layers of strong radar reflectivity at frequency of 53 MHz at which MST Radar at Gadanki, near Tirupati, India, operates. These observations, more than 2,50,000 in number, for vertical grid points, spread over all the months of the year, have helped us, among other oservation, to arrive at these conclusions. Further, the analysis suggests that the main source of strong MST radar reflectivity is not mechanical turbulence as is commonly believed.

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018195   Rajendra Kumar J;Dash S K (NO, Meteorological Office, Pune-411 005) : Inter-annual and intra-seasonal variation of some characteristics of monsoon disturbances formed over the Bay. Mausam 1999, 50(1), 55-62.

Characteristics of monsoon disturbances during drought and flood years for the period 1971-96 are studied to find out their inter-annual variations. Variations of some of the characteristics of monsoon disturbances formed over Bay during 1979-88, with respect to different monsoon conditions such as strong, weak and break monsoons, are also studied. The results show that monsoon disturbance days are higher during flood years than during drought years. Drought years are associated with higher chances of low pressure areas to intensity into depressions, less westward movement, more horizontal extent, intense pressure departure from normal in comparison with flood years. However, more monsoon disturbances tilt significantly during flood years. The rainfall associated with these disturbances is highly variable and does not depend on the intensity, horizontal and vertical extent of the individual system. More number of lows intensify into depressions during strong monsoon conditions compared to those of weak monsoon conditions. Low and depressions during strong monsoon have more westward movement and longer life period. Generally, very few lows form during break monsoons is essential for the formation depression. Synoptic systems which abate break monsoon condition and re-establish monsoon are also discussed.

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018194   Rajeevan M (NO, Meteorological Office, Pune-411 005) : Model calculations of non-cloud radiative forcing due to anthropogenic sulphate aerosol. Mausam 1998, 49(1), 45-58.

Anthropogenic sulphate aerosol particles scatter incoming solar radiation thereby perturbing the radiative budget, hence climate. Used a three dimensional radiative transfer model togetherwith the sulphate concentration fields simulated by two independent chemistry-transport models to calculate the annual cycle of the radiative forcing due to anthropogenic sulphate aerosol. The calculated forcing pattern shows large peaks over the eastern United States, southeast Europe and eastern China. The calculated annual global-mean radiative forcing is -0.50 Wm^-2 for Langer and Rodhe (1991) data and -0.49 Wm^-2 for Penner et al. [1994 (a and b)] data. The forcing was found to vary with season, with a larger forcing during northern hemispheric summer than winter. Sulphate aerosol also appreciably perturbs the lower tropospheric heating rates over northern hemispheric mid-latitudes. The forcing was also found to be sensitive to the global could cover and to the optical properties of the aerosol. The possible sources of the differences in magnitude with previous estimates are discussed. Over northern hemispheric mid-latitudes, the negative radiative forcing due to the direct effect of aerosols appreciably offsets the positive forcing due to increase in greenhouse gases. A 26-layer radiative-convective model (RCM) was also used to examine the equilibrium temperature profiles due to sulphate aerosols and increase in greenhouse gases.

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018193   Raj Y E A (NO, Meteorological Office, Chennai) : On forecasting daily summer maximum temperature at Madras. Mausam 1998, 49(1), 95-102.

Forecasting schemes based on statistical techniques have been developed to forecast daily summer (March-May) maximum temperatures of Madras. A set of optimal number of predictors were chosen from a large number of parameters by employing stepwise forward screening. Separate forecasting schemes for Madras city and airport, with lead time of 24 and 9 hr were developed from the data of 12 years and tested in an independent sample of 4 years. Maximum temperature of the previous day, normal daily maximum temperature, temperature advection index and morning zonal wind at Madras at 900 hpa level were among the predictors selected. The schemes yielded good results providing 77-87% correct forecasts with skill scores of 0.29-0.57.

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018192   Rai S S;Prakasam K S;Agrawal N (NO, National Geophysical Research Institute, Uppal Road, Hyderabad-500 007) : Pn wave velocity and Moho geometry in north eastern India. Proc Indian Acad Sci-Earth Planet Sci 1999, 108(4), 297-304.

Pn velocity has been computed across the NE India and Moho geometry constrained, using regional earthquake travel times recorded by a network of 30 seismological stations operated during February-May 1993. Using an appropriate velocity model and the arrival times at the network stations, preliminary hypocentres of 16 regional earthquakes provided by NEIC were also improved. The average Pn wave velocity in NE India has been found to be 8.5±0.2 km/s. It varies from 8.3 to 8.5 km/s beneath the Shillong Plateau, Mikhir hills and Assam valley, which is significantly higher than those in other parts of India. The crustal thickness in NE India is also high, varying from 45-49 km under the Shillong plateau and the adjoining region to 55-65 km in the convergence zone. The presence of a thick crust and high Pn velocity suggests that the lithosphere in NE India is colder, as also indicated by the observed deeper level (45-51 km) seismicity of the region.

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018191   Raghavan S (NO, , 11/16, Bayline Apartments. 2nd Cross Street Radhakrishnan Nagar, Chennai-600 041) : Tropical cyclone with the smallest eye. Mausam 1999, 50(1), 105.

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018190   Raghav K S (NO, , 228, Sheeji Nagar, Durgapura, Tonk Road, Jaipur-302 018) : On the discovery of middle eocene larger foraminifera from a limestone bed in Churu district, Rajasthan. J Geol Soc India 2000, 55(3), 269-74.

Definite Middle Eocene larger foraminifera has been found in the limestone at Sandwa. Bidasar area. Churu district in the Nagaur-Ganganagar basin, Rajasthan. Nummulites Cf. Obtuses (Sowerby) 1840 with two form viz., A form (Dia. 2.8 mm) and B form (Dia. 9 mm) are observed. In the type area of kachchh. N. Obtuses has been assigned the age of Middle Eocene. This find assigns the limestone bed to Jogira Formation and it also extends the limits of the Eocene Sea in Rajasthan by 80 km towards east.

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018189   Prasad E R;Rao C V (Department of Geophysics, Andhra Pradesh University, Visakhapatnam-530 003) : An interactive computer package for interpreting marine magnetic anomalies. J Indian Geophys Union 1999, 3(1), 1-7.

Interactive computer package for interpreting marine magnetic anomalies to delineate the basement structure has been developed both in FORTRAN and `C'. The effectiveness of Local Spectra Method and the Werner Deconvolution in delinearing the basement from magnetic anomalies is studied in comparison with that of the developed package. Re-interpretation of E - W total intensity magnetic anomaly profiles in the Northern Bay of Bengal is carried out with the developed package to delineate the basement structure. The effectiveness of the package in mapping major tectonic features like the 85°E Ridge, Ninetyeast Ridge, the Sunda Trough and an expected basement high-ridge like feature in between 85°E and Ninetyeast Ridges is demonstrated in this paper.

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018188   Pradhan B;Gouda R;Panigrahy (P G Department of Marine Science, Berhampur University, Berhampur) : Distribution of some heavy metals in the sediments of the Rushikulya estuary east coast of India. J envir Pollut 1999, 6(4), 301 5.

Concentration of four heavy metals viz., Fe. Ni. Co and Ph were estimated in the bulk sediments of the Rushikulya estuary collected from 3 stations representing the marine, gradient, and limnetic zones. Marked variations were observed both with respect to space and time in case of each element. Concentration gradient of the metals were in the order of Fe Ph Ni Co Although Co and Ni are geochemically related elements, only Ni showed good correlations with Fe (r=0.607, p … 0.001). The concentration gradient, computed concentration factor (CF) and pollution load index (PLI) suggest that the pollution stress arising out of these four metals are not serious.

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018187   Pandia M S;Dutta S K (Department of Earth Sciences, Pondicherry University, Pondicherry-605 014) : Leucogranite magmatism in Sewariya-Govindgarh areas of Rajasthan and its relevance to tungsten mineralisation. J Geol Soc India 2000, 55(3), 289-95.

In Sewariya-Alniawas-Govindgarh areas of Central Rajasthan, the Delhi metasediments are intruded by an older, biotite granite (Sewariya granite) which is equivalent to Erinpura granite occurring further south, and an younger, tourmaline leucogranite (Govind-garhgranite) which is geochemically specialised. Sewariya granite hosts wolframite bearing quartz veins along its sheared contact with mica schist of Barotiya Group. Govindgarh granite occurs in the form of small intrusive bodies within rocks of Barotiya Group, essentialy along a major ductile shear zone at the western margin of South Delhi fold belts. Our study reveals that leucogranite magmatism yielded tungsten mineralisation in Sewariya area.

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018186   Padmanabhamurthy B;Jain I (NO, Jawaharlal Nehru University, New Delhi-110 067) : Extrapolation of the vertical temperature profiles during nocturnal radiation inversion from screen temperature. Mausam 1999, 50(1), 108-10.

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018185   Narayan J P (Department of Earthquake Engineering, University of Roorkee, Roorkee-247 667) : Finite difference simulation of 2.5D acoustic wave propagation. J Geophys 1999, 20(3), 123-7.

Purpose of the 2.5 D acoustic wave simulation is to find out the 3D wave propagation effects with the help of two dimensional parameters. Linear (1991) developed a 2.5D acoustic wave equation using 3D Green's function for a constant density medium. The 2.5D simulation is of great importance because of the prevalence of the 2D survey in the seismic exploration and the cost of the 3D seismic modelling. Presents the development of 2.5D finite difference algorithm based on Liner's equation as well as the simulated results and study of various numerical artifacts. Comparisons of second as well as fourth order accurate 2.5D with 2D acoustic wave simulation results have been given. The snapshots at different times and Zero off-set response of a geological model containing hydrocarbon, faulted and pinched layer have been computed. Effectiveness of Sponge transmissive as well as Clayton and Engquist (1980) absorbing boundary conditions have been studied. After the extensive analysis it has been found that the stability condition and the requirement of number of grid points per - wavelength to avoid grid dispersion is the same as for the 2D acoustic cases.

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018184   Nageswara Rao G (Atmospheric Science Centre, Department of Meteorology and Oceanograhy, Andhra University, Visakhapatnam-530 003) : Monsoon rainfall and its variability in Godavari river basin. Proc Indian Acad Sci-Earth Planet Sci 1999, 108(4), 327-32.

Rainfall variability over a river basin has greater impact on the water resource in that basin. With this in view, the variability of the monsoon rainfall over the Godavari river basin has been studied on different time scales. As expected, the monsoon rainfall in Godavari basin is more variable (17%) than the all-India monsoon rainfall (11%) during the period of study (1951-90). Similarly, inter-annual variability of the monsoon rainfall on smaller time scales is found to be still higher and increases while going on from seasonal to daily scales. An interesting observation is that the intra-seasonal variability of the monsoon rainfall has a significant negative relationship (CC=-0.53) with the total seasonal rainfall in the basin.

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018183   Murthy V M (Department of University Science Instrumentaion Centre, Kurukshetra University, Kurukshetra-136 119) : Local scale heat advection. Proc Indian Acad Sci-Earth Planet Sci 1999, 108(4), 317-20.

Surface processes play an important role in the simulation of desertification and climate change. The study shows that enhancement of evaporation at a given place is due to surface temperature and wetness inhomogeneities compared to its surroundings. Between any adjacent dry and wet strips the induced advective heat transport changes the available net radiation between sensible and latent heat fluxes. It also accommodates a redistribution of surface energy between two adjacent inhomogeneous surface strips. A combined model of Tarpley (1994) and Ya Guo and Schuepp (1994) about the advective heat transport over dry and wet strips has been tested over Andhra Pradesh. Taking the Ananthpur district as a relatively drier region, the induced transport over the rest of the districts is estimated. This study has been done for two monsoon of 1990 and 1991. Attempts are made to identify an indexing criteria based on this study to estimate the magnitude of the heat transport.

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018182   Moharir P S;Maru V M;Srinivas S (NO, National Geophysical Research Institute, Uppal Road, Hyderabad-500 007) : Lemniscate representation for inversion of gravity and magnetic data through nonlocal optimization. Proc Indian Acad Sci-Earth Planet Sci 1999, 108(4), 223-31.

Method of representing surfaces and volumes by a set of geometric points and a small set of auxiliary parameters, based on generalization of Bernoullis notion of lemniscates is introduced. It provides for easy generation and modification of surfaces and volumes, which could be connected, disjoint or even with very irregular boundaries. This allows solving geophysical inversion problems, without constraining the anomalous volumes to some ideal or simple forms. This is illustrated by the example of joint inversion of gravity and magnetic data sets attributable to two-dimensional anomalous bodies. A nonlocal optimization algorithm called segmented Hamming scan is used for inversion. Comparison with nonlinear least-squares algorithm shows the advantages of the chosen approach. The concepts of desideratal and procedural detours are illustrated.

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018181   Mohapatra M;Thulasi Das A (NO, Meteorological Centre, Bangalore) : Analysis and forecasting of fog over Bangalore airport. Mausam 1998, 49(1), 135-42.

Fog over Bangalore airport has been analysed. The different favourable conditions on the previous night of the fog day has been studied. Attempts have been made to forecast the fog using different techniques. The composite methpod is a new objective method which provides a better technique both in terms of physical principles and statistics. The accuracy of different methods have been calculated for the purpose of comparison. The most important results of the analysis is that the frequency of duration and intensity of fog have gradually increased from the decade of 80s to the decade of 90s which may be due to the increase in pollution of air, other factors remaining unchanged.

018180   Mishra R;Richariya L K (School of Studies in Geology, Vikram University, Ujjain-456 010) : Nitrate concentration in ground waters of Beehar basin Rewa (M.P.) India. J envir Pollut 1999, 6(4), 261-4.

Nitrate contamination of groundwater in agricultural areas is a well-recognized environmental problem and has been discussed by various workers. The present study is basically aimed at evaluating cause-effect phenomenon of nitrate concentration in aquifers of Vindhyan super group, situated in the Beehar basin around Rewa (M.P.), especially with reference to drinking water. Hydrogeological survey, including water sampling of 52 wells was conducted for analyzing the flow pattern of groundwater and nitrate concentration. It has been observed that the high concentration of nitrate is causing serious health problems. The coliform bacterial count rises upto 1600/100ml High concentration of nitrates is found to be associated with leaching from fertilizers, groundslope, groundwater movement, sewage disposal and limestone mining. Nitrate concentration increases from 4 to 60 mg/L towards lower grounds of the basin, following the direction of groundwater flow. Water quality monitoring is essential for preventing the harmful concentration of nitrates in the area.

018179   Mazumdar A B (NO, Meterorological Office, Pune-411 005) : Southwest monsoon rainfall in India: I-spatial variability. Mausam 1998, 49(1), 71-8.

Results of Principal Component Analysis (PCA) in spatial mode (s- Mode) applied on a 10 years' (1977-86) data set of weekly rainfall anomalies are presented in this study. The rainfall activity has been below average in the period under study with high standard deviations mostly over low rainfal areas. Inter-subdivisional correlation values suggest predominance of broad-scale weather systems over most parts of the country. The first principal component (PC) has resemblance with the mean pattern. The second PC has been associated with active monsoon condition. The third and fourth PCs have been related to the northward progesion of the Madden-Julian oscillation and the weak monsoon condition respectively. Resemblance of spatial patterns of alternative PCs with typical strong and weak monsoon activities suggest significant contributions from certain parts of the country (northeast, southeast) towards overall rainfall activity during weak monsoon situation.

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018178   Madhwal H B (Geodetic and Research Branch, Survey of India, Dehra Dun-248 001) : GPS comes handy for determination of heights in Chilka Lake islands. J Indian Soc Remote Sens 1999, 27(1), 9-12.

Normal classical techniques of surveying could not be used in the area of chilka lake dotted with islands. Requirement of establishing height control in these islands could be met using Global Positioning System (GPS) technique. The heights at 49 locations have been established with required degree of precision in a short span of time.

018177   Madhav Kumar;Anand Prakash;Srivastava G P; Shukla M (NO, Birbal Sahni Institute of Palaecobotany, 53 University Road, Lucknow-226 007) : Dispersed organic matter (DOM types) and depositional environment of neogene sediments of Mahuadanr valley, palamu, Bihar. J Geol Soc India 2000, 55(3), 317-25.

Organic matter dispersed in the upper Tertiary sediments of Mahuadanr valley has been studied. It has been observed that the amorphous, structured terrestrial and biodegraded terrestrial organic matter represent the dominant types followed by black debris and fungal fruiting bodies. The dominance of amorphous organic matter suggests the prevalence of reducing conditions in the basin, particularly during the deposition of the lower part of the sequence. The conditions gradually transformed into oxidising environment during the deposition of upper part of the succession. Besides this, the presence of black debris indicates moderate oxidising environment in the source area and also during the transport of the organic matter.

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018176   Kumar C P (NO, Hard Rock Regional Centre, National Institute of Hydrology, Belgaum) : Evaporation from shallow water table through layered soil profiles. ISH J Hydraul Engng 1999, 5(2), 65-75.

Estimates the steady state evaporation rates from layered soils in the presence of high water table under isothermal conditions. A finite difference numerical scheme based upon the one-dimensional Richards equation has been employed to estimate the evaporation rates from a two-layered soil profile overlying a shallow water for appropriate initial and boundary conditions. The method takes into account the relevant atmospheric factors and soil moisture characteristics of the two layers. The effects of sequence and thickness of the soil layers and water table depth on the evaporation rates have been examined.

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018175   Kulkarni S B;Wakalkar V M (NO, Central Water and Power Research Station, Khadakwasla Research Station, Pune) : Performance of anti-erosion works for protection at Palasbari-Gumi area along the river Brahmaputra. ISH J Hydraul Engng 1999, 5(2), 22-30.

Describes the results of model studies of some anti-erosion works carried out in connection with the erosion of flood embankments on the Brahmaputra River. Also describes some salient aspects of performance of anti-erosion works and compares them with model results.

018174   Krishna K S;Gopala Rao D;Subba Raju L V; Chaubey A K (NO, National Institute of Oceanography, Dona Paula, Goa-403 004) : Paleocene on-spreading-axis hotspot volcanism along the ninetyeast ridge: an interaction between the Kerguelen hotspot and the Wharton spreading center. Proc Indian Acad Sci-Earth Planet Sci 1999, 108(4), 255-67.

Investigations of three plausible tectonic settings of the Kerguelen hotspot relative to the Wharton spreading centre evoke the on-spreading-axis hotspot volcanism of Paleocene (60-54 Ma) age along the Ninetyeast Ridge. The hypothesis is consistent with magnetic lineatins and abandoned spreading centers of the eastern Indian Ocean and seismic structure and radiometric dates of the Ninetyeast Ridge. Furthermore, it is supported by the occurrence of ocean andesites at Deep Sea Drilling Project (DSDP) Site 214, isotopically heterogeneous basalts at Ocean Drilling Program (ODP) Site 757 of approximately the same age (59-58 Ma) at both sites. Intermix basalts generated by plume-mid-ocea ridge (MOR) interaction, exist between 11° and 17°S along the Ninetyeast Ridge. A comparison of age profile along the Ninetyeast Ridge betwen ODP Sites 758 (82 Ma) and 756 (43 Ma) with similarly aged ocenic crust in the Central Indian Basin and Wharton Basin reveals the existence of extra oceanic crust spanning 11° latitude beneath the Ninetyeast Ridge. The extra crust is attributed to the transfer of lithospheric blocks from the Antarctic plate to the Indian plate through a series of southward ridge jumps at about 65, 54 and 42 Ma. Emplacement of volcanic rocks on the extra crust resulted from rapid northward motion (absolute) of the Indian plate. The Ninetyeast Ridge was originated when the spreading centres of the Wharton Ridge were absolutely moving northward with respect to a relatively stationary Kerguelen hotspot with multiple southward ridge jumps. In the process, the spreading centre coincided with the Kerguelen hotspot and took place on-spreading-axis volcanism along the Ninetyeast Ridge.

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018173   Kashyapi A;Das H P (NO, Meteorological Office, Pune-411 005) : Requirement of heat unit and agrometeorological indices in selected wheat growing zones. Mausam 1999, 50(1), 63-70.

Wheat growing ET-stations (viz., Jorhat, Varanasi, New Delhi, Ludhiana, Raipur, Jabalpur, Akola, Bellary, Banswara and Jodhpur) situted in arid to perhumid climatic zones were selected. Heat unit and three agrometeorological indices, viz., ARI (agroclimatic rainfall index), YMI (yield moisture index) and AI (aridity index) were computed at various growth stages of wheat crop using lates available five years data for each of the stations. The crop degree days requirement varied from 1580 (at Jorhat) to 2350 (at Akola) with the maximum requirement at tillering and milk stages. All the stations (except Jorhat) recorded ARI values less than 25%, while for the stations in peninsular and western India, the values were even below 10%. Low cumulative YMI values were obtained in peninsular and western India, while high values were observed over eastern India. The wheat crop did not experience any aridity during tillering to flowering stages for all the stations (except Bellary and Banswara). High values of AI were observed at early and late crop growth stages. Negative correlation was obtained between AI and ARI with the highest value (-0.89) observed at New Delhi. Depending upon this study, the wheat growing areas were divided into five zones.

018172   Kane R P (NO, Instituto Nacional de Pesquisas Espacias-INPE, Caixa Postal 515, 12201-97-Sao Jose dos Campos, SP, Brazil) : Periodicities and ENSO relationship of the seasonal precipitation over six major sub-divisions of India. Mausam 1999, 50(1), 43-54.

Spectral analysis of the 1848-1995 (148 year) time series of Sontakke and Singh (1996) representing estimates of summer monsoon (June-September) precipitation amounts over six homogeneous zones (Northwest NW, Northcentral NC, Northest NE, West Peninsular WP, East Perinsular EP, South Peninsular SP) and the whole of India (AI) revealed significant periodicities in the QBO and QTO regions (2-3 years and 3-4 years) as also higher periodicities, some common to all zones. To study the ENSO relationship, a finer classification of years was adopted. For the All India summer monsoon rainfall as also for all the zones except NE, Unambiguous ENSOW (where EI Nino existed and SOI minima and SST maximam were in the middle of the calendar year i.e., May-August), were overwhelmingly associated with droughts and the cold (C) events were associated with floods. For other types of events, the results were uncertain and a few extreme rainfalls occurred even during some Non-events.

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018171   Kane R P (NO, Instituto Nacional de Pesquisas Espaciais - INPE, C Postal 515, 12201-970 - Sao Jose dos Campos, SP, Brasil) : El Nino, southern oscillation, equatorial eastern pacific sea surface temperatures and summer monsoon rainfall in India. Mausam 1998, 49(1), 103-14.

For the 120 years (1871-1990), every year was designated as an El Nino (EN), or Southern Oscillation (SO), minimum or a combination of these, or none. For all India summer monsoon rainfall (ISMR), unambiguous ENSOW [SO and W (warm events) in the middle of the calendar year] seemed to be best associated with droughts and events of type C (cold events) were best associated with floods. However, some droughts occurred without the presence of EN related events and some floods occurred even in the presence of EN related events. In these cases, other parameters such as Eurasian snow cover or stratospheric wind QBO might have had a larger influence.

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018170   Kanade V V;Abhyankar V V;Prabhu S V;Desikan V (NO, Meteorology Office, Pune-411 005) : Cosine response of pyranometers - measurements at Pune. Mausam 1998, 49(1), 37-44.

Among the vaious characteristics that determine the overall acuracy and performance of a pyranometer, the strict adherence to the cosine law is an important one. But this cosine response is difficult to realise and to correct for. The cosine response of various types of pyranometers available at Pune was determined on the optical set up in Central Radiation Laboratory. The results of these are presented briefly.

018169   Islam M N;Uyeda H;Kikuchi K (NO, Bangaladesh University of Engineering and Technology, Dhaka, Bangaldesh) : Development of tropical cloud clusters analyzed with satellite data. Mausam 1999, 50(1), 83-90.

In order to understand the general characteristics of the cloud clusters in the TOGA-COARE domain, analyses were performed on 10 days (3-12 November, 1992) of satellite data. Four large cloud clusters (LCCs) and one small cloud cluster (SCC) were analyzed on 3-5 November, 1992. Three of LCCs were found to be 750-1150 km, lasted 14-28 hours in their lifetime, and propagated with a speed of about 6 m/s. NP The SCC has a horizontal length of above 200 km, and lasted approximately 12 hours and propagated with a speed of -13 m/s. The vertical structure of the cloud/clusters were analyzed using GMS-IR data on 3-12 November, 1992, after defining a cloud by the enclosed boundary of TBB ≤230 K. The characteristics of the short-lived (<60>1 day) cloud were found different from those of longlived (<62>1.5 days) cloud clusters.

018168   Handique G K (Oil & Gas Division, Reliance Industries Limited, , Mumbai-400 055) : The mighty Brahmaputra river - hydrocarbon potential, problems and challenges. J Indian Geophys Union 1999, 3(1), 51-61.

Mighty Brahmaputra rive system with over hundreds tributaries containing one of the biggest single concentration of hydel power potentials of the world, is also expected to hold good hydrocarbon resources beneath the rive bed and its neighbouring swamy areas in the Upper Assam valley (Handique et al. 1991). The rive stretches over 250 kms in length with width varying from 5 to 15 kms in the study areas. Barring aeromagnetic data over the area which show a number of `highs', there are no seismic data available so fat to confirm these `highs' due to logistic problems for seismic data acquisition. Thus the entire area has so far remained practically unexplored. The hidden basement ridge which is the continuation of the exposed Precambrian basement of the Mikir hills, runs in a ENE-WSW direction almost parallel and in a close proximity to the Brahmaputra river in Upper Assam valley. A number of major faults running more or less parallel to the axis of the hidden basement ridge with majority dipping towards southeast in the southern flank of the regional ridge and the associated transverse faults divide the region into different zones. These structural elements coupled with the depositional environment of the Tertiary sediments have played a major role in the distribution of hydrocarbons in the Assam shelf zone.

018167   Gupta P K;Sri Niwas;Rastogi A (Department of Earth Sciences, University of Roorkee, Roorkee-247 667) : EM21NV - a finite difference based algorithm for two-dimensional inversion of geoelectromagnetic data. Proc Indian Acad Sci-Earth Planet Sci 1999, 108(4), 233-53.

Efficient finite difference based 2D-inversion algorithm, EM21NV, for geoelectromagnetic data has been presented. The algorithm is tested rigorously by setting up exercises of diverse nature and of practical significance. The stability of the algorithm is established by inverting the synthetic response corrupted with Gaussian noise. The inversion experiments are aimed at studying: relative performance of response functions; inversion quality of E- and B-polarization data; efficacy of single multi-frequency data inversion; minimum number of frequencies and observation points needed for successful data inversion. It has been observed that Magneto-telluric data deciphers better the vertical position of the target and Geomagnetic Depth Sounding data deciphers the horizontal variations in better way. The conductive and resistive bodies are better resolved by inversion of E- and B-polarization data respectively. The results of multi-frequency inversion imply that the increase in the number of frequencies does not necessarily enhance the inversion quality especially when the spread of observation points is sufficiently large to sense the target. The study of a minimum number of observation points highlights the importance of single point inversion that furnishes useful information about the inhomogeneity.

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018166   Guhathakurta P (NO, India Meteorolgical Department, Pune-411 005) : Neural network model for short term prediction of surface ozone at Pune. Mausam 1999, 50(1), 91-8.

New method for short term prediction of air pollution is presented using the neural network technique. Due to increase in industrial and anthropogenic activity, air pollution is a serious subject of concern today. Surface ozone can be considered as a representative of total atmospheric oxidants and of air pollution. A three layer neural networ model using the technique of adaptive pattern recognition is developed. The model can predict the mean surface ozones between 12 and 13 hours (hour of maximum concentration). The model can perform well both in training and independent periods. The classical methods of short term modelling are not reliable enough. The method can also be used for short term predicition of other air pollutants.

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018165   Ghosh N;Wadhwa R S;Chaudhari M S; Chandrashekhar V;Saha A (Central Water and Power Research Station, , Pune-411 024) : Underwater seismic reflection survey for development of a port near Tarapur, Maharashtra. J Indian Geophys Union 1999, 3(1), 37-44.

Marine geophysical surveys have been carried out in the shallow water off Alewadi near Tarapur to assess the seabed and subseabed conditions for development of a major port and navigational channel. The shallow seismic reflection results reveal in general, three subsurface reflectors. On correlation with the available borehole data these reflectors correspond to sea-bed, sediments/weathered rock and good quality basalt rock. The bedrock was found to be shallower (8 14 m) on the eastern boundary as compared to that on the western boundary (16-20 m). The depths to bed-rock from seismic survey agreed well with those inferred from post-survey drilled boreholes. On the basis of findings of seismic survey, the alignment of the breakwaters was shifted towards north from the originally proposed location. Also, depending on the cost of dredging, three alternative proposals are being worked out.

018164   Ghadekar S R;Miskin R B (Department of Agric Engg and Meteorology, PKV College of Agriculture, Nagpur) : Characterization of monsoon rainfall for sorghum (Sorghum vulgare Pers) and its response to typical rainfall patterns. Mausam 1998, 49(1), 115-20.

Twenty eight years (1962-89) rainfall of Nagpur was analysed and the rainfall suitability at various probability levels for sorghum crop was studied. The total rainfall during kharif season (25-39th MW) was 861.50 mm. Normal rainfall/week exceeded 50 mm during 12 weeks (25-36th MW) which declined successively for these week (37-39th MW). The coefficient of variation (CV) ranged between 74.3% (25th MW), ro 144.7% (39th MW). The rainfall at 50% probability level was well distributed during 12 weeks (25-36 MW) ranging between 44.5 to 36.3 mm being adequate and sufficient (<62> 20 mm/week) for sorghum crop considering its weekly demand (21-35 mm/week). Typical rainfall patterns representing the situation were defined on the basics of their repetitiveness. Out of four typical rainfall patterns studied, the one with lowest rainfall (458.4 mm/season and 30.56 mm/week) fetched the highest yield (865. kg/ha) which ensured adequate rains during the various growth stages except maturity. Excessive rainfall (<62> 100 mm/week) and deficient rainfall (<62> 20 mm/week) during every stage were inadequate. Rainfall atleast 30.56 mm/week was mosat adequate.

018163   Gangadharan V K;Sasidharan N V;Santhosh K (NO, Meteorological Centre, Thiruvananthapuram) : Study on heat island intensities at Thiruvanathapuram on a cold winter night. Mausam 1999, 50(1), 106-8.

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018162   Gaitan Vaz G (NO, East Coast Operations II, Marine Wing, Geological Survey of India, 41, Kirlampudi Layout, Visakhapatnam-530 017) : Verdine and glaucony facies from continental margin of Chennai, Bay of Bengal. J Geol Soc India 2000, 55(3), 297-306.

Green and brownish green grains associated with surficial sediments of outer continental shelf and subsurface sediments of upper slope of Chennai have been investigated for their distribution.The green and brownish grains account for 40% of the sediments in the outer continental shelf while in the upper slope the green grains account for 20-90% of the sediments. X-ray diffractograms reveal that the grains from outer shelf are mainly composed of Phylite V clay mineral of the verdine facies and a mixture of detrital clays. The grains from the upper slope constitute glauconitic smectite and glauconitic mica of the glaucony facies respectively. Their distribution pattern signifies the palaeobathymetric and palaeoenvironmental conditions of the area. Glaucony facies in upper continental slope apparently belong to the period of Last Glacial Maximum (LGM) and verdine facies in outer continental shelf to subsequent transgression.

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018161   EL-Shazly S M;Abdelmageed A M;EL-Adam M (Department of Physics, Faculty of Science, South Valley University, Qena/Upper Egypt) : Solar radiation characteristics at Qena/Egypt. Mausam 1998, 49(1), 59-70.

Measurements of the hourly global solar radiation(G) and its diffuse component(D) on a horizontal surface have been carried out in Qena/Upper Egypt in the period from June 1992 to May 1993. The corresponding diffuse fraction (D/G) is calculated. Diurnal variations of the results have been studied. Also the daily totals values and its monthly and seasonal average as well as their frequency distributions were computed and examined. The seasonal and climatic effects on the fluctuation of the results are discussed. These effects were particularly large during Spring and winter months owing to the high fluctuation of the atmospheric conditions with respect to amount of clouds, water content, and concentration of aerosol dust particles. The influence of clouds is also considered. It shows small effct on the results (4.5%), reflecting the low degree of cloudiness in the region. The relation between the diffuse fraction and clearness index (G/G_o) shows that most of the points lies in the region of the high availability of the incoming solar radiation. In general the study shows clearly the abundance of solar energy in Qena/Egypt, and the suitability of its climate for using it in different applications.

018160   Dwivedi H (NO, National Environmental Engineering Research Institute, Nehru Marg, Nagpur-440 020) : Long term effects of polyaromatic hydrocarbon (Naphthalene) on cat fish heteropneustes fossilis. J Ecobiol 2000, 12(1), 37-43.

Toxicity of napthalene to immature cat fish Heteropneustes fossils and its histopathological effects and behavioural responses were studied in the laboratory at doses varying from 0.5 mg/ to 2 mg/l. The major behavioural effects observed were reduction in mobility, food consumption and loss in weight. The histopathological effects were prominant at 2 mg/l and 1 mg/l doses, whereas at 0.5 mg/l, no effects were observed during exposure of 15 days. The major histopathological effects being dissolution of cytoplasm, syncytium formation, oedema formation, necrosis, eosinophilic material and formation of tumour. Increase in dose and duration of exposure resulted in formation of tumour. The toxic effects observed at 2 and 1 mg/l dose of napthalene over a period of 30 and 45 days to H.fossilis were irreversible and resulted in the deth of the fish.

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018159   Dutta S N;De U S (NO, Meteorological Office, Pune-411 005) : Diagnostic study of contrasting rainfall epochs over Mumbai. Mausam 1999, 50(1), 1-8.

Attempt has made to diagnose the synoptic features and some dynamic and thermodynamic parameters associated with contrasting rainfall situations (on consecutive days) during the monsoon season, over Mumbai. Study has been made for two contrasting monsoon years, viz, 1987 (Bad monsoon year) and 1988 (Good monsoon year). For this study R.S data of Mumbai have been used. In many cases heavy rainfall on an isolated day over Mumbai is associated with the following synoptic systems a trough on sea level chart running along west coast through Maharashtra Coast and a cyclonic circulation (CYCIR) over Gujarat in the lower/middle tropospheric level. At least one of the above two systems ceased to exist on the days of light rainfall. Weighted average value of moist static energy is more on the day of heavy rainfall. In most of the cases convective available potential energy (CAPE) is also more on the heavy rainfall. LFC, on most of the cases, is seen to have lowered down on the days of heavy rainfall. Variation in upper air flow pattern and scorer parameter also very interesting clues to variation of rainfal on contrasting days.

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018158   Dugam S S;Kakade S B (NO, Indian Institute of Tropical Meteorology, Pune-8) : Global temperature and monsoon activity. Proc Indian Acad Sci-Earth Planet Sci 1999, 108(4), 305-7.

Attempt has been made to search a new parameter for the prediction of the Indian summer monsoon rainfall. For this purpose the relationship of the global surface air temperature of four standard seasons viz., Winter (December-January-February), Spring (March-April-May), Summer (June-July-August), Autumn (September-October-November) with the Indian summer monsoon rainfall has been carried out. The same analysis is also carried out with surface-air temperature anomalies within the tropical belt (30°S to 30°N) and Indian summer monsoon rainfall. For the present study data for 30 years period from 1958 to 1988 have been used. The analysis reveals that there is a strong inverse relationship between the monsoon activity and the tropical belt temperature.

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018157   Dhurandhar A;Saxena D N (Atomic Minerals Division, Dept of Atomic Energy, , West Block VII, R K Puram, New Delhi-110 066) : Intergrated airborne gammaray spectral and satellite data analysis for U and REE mineralisation - a case study from north Sagobandh area, district Sonbhadra, Uttar Pradesh, India. J Indian Soc Remote Sens 1999, 27(1), 43-57.

Airborne gamma ray spectrometric (AGRS) and magnetic (AM) surveys were undertaken between 1986-1987 by Atomic Minerals Division, to locate uranium mineralisation along Son-Narmada rift zone. The imaging and interpretation of gridded AGRS data revealed many areas of anomalous radio elemental concentrations. These areas have been defined by taking thresholds as U ≥ 6 ppm. Th ≥ 24 ppm. K ≥ 2.3% and Total counts ≥ 5000 cps. The AGRS data integration with the satellitc data viz., Landsat Multi spectral Scanner (MSS), Thematic Mapper (TM), and IRS LISS II data on different scales indicated the lithostructural controls of uranium mineralisation and also the predominance of the potash metasomatism in the vicinity of the southern Son rift soda metasonatism further away in the south. Systematic follow up ground checking of the target area located in the North Sagobandh area resulted in delineating the areas of K metasomatism, anatexis and grissenisation as the areas showing ≥ 2.3%K values. The depleted K., Th., and high U/Th values show zones of albitisation and oligoelasistion. The trends of radiometric breaks depicted by total counts distirbution patterns defined the tectonstratigraphic boundaries. Besides these 26 radioactive anomalies with grades ranging from eU 30./0/12-0.18%, U30x B/r <60>0.01-0.3% and ThO2 0.00.5-0.1% having strike length 50-500 meters and outcrop thickness .5-2.5 meters. ten locations of inland riverine and placers of heavy minerals containing REE bearing minerals i.e. xenotime, monazite, rutile, ilmenite, ziron and traces of columbite-tantalite have been identified by using thorium and mixed source (U+Th) anomaly map. These sand placers have channel lengths of 100 <62>500 meters and width of 1-2.5 meters, containing 1.5%-9.04% heavy minerals.

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018156   Desikan V;Prabhu S V (NO, Meteorology Office, Pune-411 005) : Variations in ÅAngstrom's wavelength exponent at Pune-411 005. Mausam 1998, 49(1), 27-36.

Solar irradiance in its passage through the atmosphere gets attenuated by scattering and selective absorption processes. Particulate matter cause scattering in the visible part of the spectrum. Spectral radiometric studies enable the determination of the extinction factors and hence the values of wavelength exponent α for each measurement. α values are much lower than the classic value of 1.3, now being used in the determination ÅAngstrom Turbidity Coefficient β. The value of α is generally found to be of the order of 0.5. In presence of large particles, particularly hygroscopic ones, values reach nearly zero and even negative values, suggesting the possibility of attenuation of irradiance in red wavelengths by absorption processes.

018155   Choudhury K;Saha D K;Ghosh D C (Central Geophysics Division, Geological Survey of India, Calcutta-700 016) : Urban geophysical studies on the groundwater environment in parts of Gangetic delta. J Geol Soc India 2000, 55(3), 257-67.

Mixing of subsurface fresh and brackish/saline water has given rise to pollution in the aquifer and consequent environmental problems in the urban and semi-urban areas of the Howrah District of West Bengal. Also, overdrawal of groundwater has adversely affected the water table resulting in increase in salinity and possible threat to the civil structures. In order to suggest some remedial measures to arrest further deterioration of the environmental problems due to excessive and random pumping of groundwater, vertical electrical soundings (VES) using Schlumberger configuration have been carried out at 70 locations. Geoelectrical sections, isoresistivity maps at different depth levels as well as total transverse resistance (TTR) map of the area have been prepared. Analysis of these interpreted sections and maps have been able to ascertain the resistivity and geohydrological characteristics of the subsurface layers, map the aqifers and saline/brackis groundwater zones and suggest measures for safeguards against groundwater pollution. Further, prospective groundwater zones and an old channel of Bhagirathi river are identified within the highly conducting brackish deltaic area. The litho-sections brought out by the interpretation of survey data would be useful to the city planners for land use, foundation studies and related utilities.

018154   Chandramohan T;Joseph A K (NO, National Institute of Hydrology, Belgaum) : Two-dimensional finite element modelling of an Indian estuary. ISH J Hydraul Engng 1999, 5(2), 55-64.

In shallow water bodies, horizontal components of flow quantities are more significant than vertical components, and vertically integrated form of hydrodynamic equations can be employed. FESWMS-2DH, developed by USGS, is a numerical model which uses finite element method to solve the system of two dimensional equations and is used in the study to simulate the hydrodynamics of Cochin estuary. Calibration and validation have been done using velocity measurements at 11 observation points by adjusting the model parameters like roughness coefficient and eddy viscosity. It is found that the model is capable of simulating the circulation pattern resulting from various scenarios.

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018153   Camerlengo A L;Saadon M N (Faculty of Applied Sciences and Technology, Universiti Kolej Terengganu Mengabang Telipot, 21030 Kuala Terengganu, Malaysia) : ENSO sea-level variations in peninsular Malaysia and Sabah. Ultra Scient phys Sci 1999, 11(3), 288-94.

Sea level variations both in Peninsular Malaysia and Sabah during the 1986-87 and the 1991-93 ENSO events are analyzed. The reverse water mass transport observed in the two, the Malacca Straits and in Sabah may be attributed to the abatement of the trade winds during ENSO events.

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018152   Bhatla R;Chattopadhyay J (Department of geophysics, Banaras Hindu University, Varanasi-221 005) : Association between mid-latitude circulation and Indian monsoon rainfall. Mausam 1999, 50(1), 37-42.

The statistical relationship between the summer monsoon rainfall over India and mid-latitude general circulation at the 500 hPa level was investigated for the period 1971-1989. The index used to characterise general circulation feature is the perturbation of the zonal flow (ratio of meridional to zonal index) for the latitudinal band 35°N-70<14>N over different geographical area and the hemisphere. It was found that the perturbation of the zonal flow during preceding January over the geographical sector I (45°W-90°E) shows significant relationship with the subsequent Indian summer monsoon rainfall in an inverse manner. Thus the perturbation of the mid-latitude circulation during preceding January over the geographical sector I seems to be a useful predictor of the subsequent Indian monsoon rainfall. Significant simultaneous inverse relationship also exists between perturbation of mid-latitude zonal flow during July to September 2 (90°E-160°W) and summer monsoon rainfall over northwest India.

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018151   Basak P;Shaw R K;Agarwal B N P (Department of Applied Geophysics, Indian School of Mines, Dhanbad-826 004) : Spectral analysis of short gravity profiles by Maximum Entropy Method. J Indian Geophys Union 1999, 3(1), 9-14.

Energy spectrum of a gravity anomaly profile computed via conventional methods, viz., the periodogram approach or from the Fourier transform of the corresponding auto correlation function often exhibits oscillatory behaviour. Thus, the depth determined from the spectral decay rate is biased and erroneous especially when the observations are limited over a profile of short length. The situation can be improved by using maximum entropy method (MEM) for computation of the energy spectrum. MEM predicts non zero auto correlation values outside the available lags, thereby virtually extending the profile length. Depths computed from MEM spectra of the gravity anomalies over 2D horizontal cylinder reveal that a profile length of 4 times the source depth and a random noise up to 10% of the simulated anomaly can provide reasonable depth estimates. A field example hs been presented to demonstrate the applicability of MEM in gravity data interpretation.

018150   Babu Rao V;Srinivasulu T (NO, National Geophysical Research Institute, Hyderabad-500 007) : Where and how of prospecting for diamonds in Andhra Pradesh, South India. J Geophys 1999, 20(3), 103-16.

Exploration for Diamonds is synonymous with the exploration for Kimberlite and Lamproites which were recognised as the primary source rocks for the Diamonds. Andhra Pradesh is known as "Home of Diamonds" since historic times as world famour Diamonds like Kohinoor, Orloff and Pitt were won from the gravels of Krishna valley. The economic value of the Diamonds, needs of the domestic industry and the spate of recent discoveries of primary sources in Andhra Pradesh call for a relook into the probable search in Andhra Pradesh. The exploration of kimberlites and lamproites is dependent on the geological environment and requires multi-disciplinary and integrated approach. The rarity and the smallness of the Kimberlite diatrems and dykes and the wide range of variation of their physical properties make the exploration for kimberlites a challenging task. The role of geophysics in diamond exploration is discussed in the light of the past experience.

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018149   Asoi Lal;Sunder R S;Joshi S P (NO, Meteorolgical Office, Pune-411 005) : Effect of eastward moving cloud clusters over northwest India and neighbourhood on the Indian summer monsoon. Mausam 1999, 50(1), 25-30.

Number of studies have been made relating to the prediction of date of onset and also the activity of southwest monsoon over India. Attempt has been made to link the behaviour of rainfall in northern and peninsular India to the satellite cloud cluster over the region of Afghanistan, Iran and northwest India. The monsoon rainfall over India commences in June. Hence variation of monsoon rainfall pattern with the movement of cloud clusters from northwest in pre-monsoon and monsoon months have been studied to elucidate the pattern of changes. The variability of monsoon performance largely depends on the number and movement of cloud clusters over northwest region during pre-monsoon and monsoon months.

018148   Ashok Kumar (NO, Bihar Council on Science and Technology, B-Block, IIIrd Floor, Maurya Lok Complex, Patna-800 001) : Sustainable utilisation of water resource in watershed prespective - a case study in Alaunja watershed, Hazaribagh, Bihar. J Indian Soc Remote Sens 1999, 27(1), 13-22.

Landuse, soil and surface water body maps have been prepared using remotely sensed data. DBTM has been generated based on depth of brasement information derived from geophysical data to provide information regarding aquifer geometry, fracture zones and sub-surface basins. Analysis indicated that surface and groundwater resources have potential to irrigate 53 per cent of geographical area of the watershed. But at present, this available potential has been utilised only to irrigate 7.03 per cent area of the watershed. Feasibility for large scale development of groundwater through dugwell is possible only in 2 per cent area of watershed can not be utilised through dugwells. The surface water potential is also poorly utilised.

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