003465   Rao P S P;Momin G A;Safai P D;Ali K;Naik M S; Pillai A G (NO, Indian Institute of Tropical Meteorology, Dr Homi Bhabha Road, Pashan, Pune-411 008) : Aerosol and trace gas studies at Pune during INDOEX IFP-99. Curr Sci 2001, 80(Apr), 105-9.

Analysis of the data revealed that during the winter months (January and February), TSP concentrations were less compared to those in the beginning of summer (March). High concentrations of TSP in March may be due to the increased convective activities. The mass size distribution of aerosols showed bimodal distribution with one peak in fine size (<60> 1 μm radius) and another in coarse size. The contribution of coarse and fine particles to the total aerosol mass was more or less same in January, whereas coarse particles dominated in March. The chemical composition of water soluble aerosols showed that even though the concentrations of acidic components (SO4 and NO3) were high, they were being neutralized by alkaline components such as NH4, Ca, K and Mg. Hence, the aerosols are still in the alkaline range. On an average, the concentration of trace gases (SO2, NO2, O3 and NH3) are within the world background values, however, on some occasions, the SO2 NO2 and O3 concentrations have exceeded.

2 illus, 5 tables, 13 ref

003464   Pillai P S;Jhurry D;Krishna Moorthy K (Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram-695 022) : Aerosol optical depth studies during INDOEX : comparison of the spectral features over coastal India with the pristine southern hemispheric environment over Mauritius. Curr Sci 2001, 80(Apr), 138-44.

Results indicate that there is a significant hemispherical difference for aerosol spectral optical depth (AOD at shorter wavelengths (λ≤ 650 nm), while at the longer wavelengths (λ≤ 650 nm), AOD does not show any appreciable variation with location. The spectral variation of AOD at TVM and MCY (for march 1998) depicted a similar pattern with the AOD values between 0.5 and 0.6 at shorter wavelengths and between 0.2 and 0.4 at longer wavelengths. In contrast to this, the AOD at MRU are very low, lying in the range 0.1 to 0.2 in the shorter wavelengths, whereas at the longer wavelengths the AOD values are more or less comparable (in the range 0.2 to 0.4) with the northern hemispheric stations. The cruise data clearly showed that the transition occurs generally across the ITCZ. The increased AOD at shorter wavelengths in the northern hemisphere indicates higher concentration of sub-micron aerosols in these environments arising mainly due to anthropogenic activities, while the AOD at the longer wavelengths is attributed mainly to be of marine origin. In the post-cruise period, the spectral optical depths showed a gradual increase from March to June at MRU, while at TVM, the pattern followed more or less the climatological mean. By May the AOD at shorter wavelengths decreased at TVM (due to increased rainfall) and by June, the AOD at TVM are very much comparable with those seen at MRU.

11 illus, 2 tables, 16 ref

003463   Peshin S K;Mandal T K;Smit H G J;Srivastava S K;Mitra A P (India Meterological Department, , Lodi Road, New Delhi-110 012) : Observations of vertical distribution of tropospheric ozone over Indian Ocean and its comparison with continental profiles during INDOEX FFP-1998 and IFP-1999. Curr Sci 2001, 80(Apr), 197-208.

East-west cross-section of ozone concentration in the troposphere along 20°S and 15°N may be characterized as the background value of pristine and continental air on the northern and southern side of the equator, respectively. Though back trajectory analysis indicates that flow of air masses is mostly from the Indian subcontinent as well as south-east Asian region, it is difficult to distinguish the degree of relative contribution of continental flow to ozone concentration over the Indian Ocean. The comparison between marine and continental ozone profiles suggests that the northern side of the Inter Tropical Convergence Zone (ITCZ) resembles the continental profiles as observed over the Indian subcontinent and African region, rather than east Asian region.

12 illus, 1 table, 58 ref

003462   Patra A K;Das S;George J P;Paliwal R K;Mitra A P (National Centre for Medium Range Weather Forecasting, , Mausam Bhavan Complex, Lodi Road, New Delhi-110 003) : Variability of convective heating and moistening using simplified Arakawa Schubert convection scheme during INDOEX IFP-99. Curr Sci 2001, 80(Apr), 25-9.

Study the variability of convective heating and moistening in the above two cases using Simplified Arakawa-Schubert convection scheme incorporated in the single column model. Vertical profiles of temperature, specific humidity, wind (u,v,w), sensible and latent heat fluxes, temperature and moisture advective forcings were used for the initialization of the SCM. The first three inputs of the above variables were obtained from the analysed data of the T80 Global Circulation Model in which INDOEX data were used for the data assimilation. The large scale advective forcings were also taken from the T80 GCM over the INDOEX observation points. The SCM has been integrated with 15 min time step in a fully prognostic way to obtain the convective heating, moistening, convective rainfall and cloud base mass flux for the above two dates. The results showed that the convective heating and moistening, were larger on the cloudy day than those on the fairweather day. The distribution of hourly averaged values of convective heating and moistening showed that existence of multiple cloud types on the cloudy day.

003461   Parameswaran K;Nair P R;Rekha Rajan; Balasubrahamanyam D (Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram-695 022) : Spatial distribution of aerosol concentrations over the Arabian sea and the Indian Ocean during IFP of INDOEX. Curr Sci 2001, 80(Apr), 161-5.

During the intense field phase of the INDOEX, a high volume sampler was sailed on cruise to collect aerosol samples from different oceanic environments. The variation of aerosol mass concentration (m) with latitude and longitude was studied. The aerosol concentration near the West Coast is <126> 40 μg/m³, which is almost twice the amount that was observed in this region during FFP-98. This is in agreement with the data obtained from surface measurement at Trivandrum. An enhancement in m was observed <126>5°N associated with the convergence of air stream coming over Arabian Sea, Bay of Bengal and the eastern parts. During the cruise period, the ITCZ located around 4°S is rather broad and less dynamic. A significant decrease in m was observed in this region. A significant enhancement in m was observed around 20°S during the up leg along the longitudinal sector 70-75°E. During the return leg an enhancement in m is observed in the northern hemisphere, with increasing latitude (in the Arabian Sea sector). The aerosol loading increases further north of Goa towards the Bombay coast. The overall spatial pattern of m during IFP-99 compares favourably with that observed during FFP-98.

4 illus, 5 ref

003460   Parameswaran K;Nair P R;Rajan R (Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram-695 022) : Aerosol loading in the atmospheric boundary layer at Trivandrum coast and in the adjoining Oceanic environments during the FFP and IFP of the INDOEX. Curr Sci 2001, 80(Apr), 151-60.

This size index shows a decrease during IFP-99 period, indicative of a relative increase in larger size particles. The mixing region aerosol optical depth also is relatively high during IFP-99. The mass concentration measured along the West Coast on the cruise shows an increase during IFP-99. Along the coast, as the ship sails from Goa towards south, the aerosol mass concentration first decreases and then increases as the ship approaches Cochin. This increased concentration remains steady up to the southern tip of the Indian peninsula. A significant decrease in m was observed in the ITCZ region. The aerosol concentration south of ITCZ was less than that in the North (in the Arabian Sea region). An increased concentration of aerosols was observed in the mid-Arabian Sea oceanic environments, which was attributed to advecting aerosols due West and North.

10 illus, 2 tables, 22 ref

003459   Parameswaran K et al (Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram-695 022) : Lidar observations of aerosol layers just below the tropopause level during IFP-INDOEX. Curr Sci 2001, 80(Apr), 166-70.

Lidar system has been used at Gadanki (13.5°, 79.2°E) to study the characteristics of aerosol layer (cloud) occurring just below the tropical tropopause. The preliminary results of the lidar observations indicate that the cloud occurs <126> 2 km below the tropopause. The top and bottom edges of the cloud have propensity for ice crystal presence with liquid droplets/vapours in-between. The clouds show temporal fluctuations (in their backscattering ratio) with temporal scales of the order of 30-90 min.

9 illus, 10 ref

003458   Nair P R;Rekha Rajan;Parameswaran K;Abraham A;Jacob S (Space Physics Laboratory, Analytical Spectroscopy Division, Vikram Sarabhai Space Centre, Thiruvananthapuram-695 022) : Chemical composition of aerosol particles over the arabian sea and the Indian ocean regions during the INDOEX (FFP-98) cruise - preliminary results. Curr Sci 2001, 80(Apr), 171-5.

Aerosol samples collected from the marine environment of Arabian Sea and Indian Ocean using a high volume aerosol sampler during the first field phase of the Indian Ocean Experiment (INDOEX) were analysed to study the mass concentration of cations like Na, K, Mg, Mn, Zn, Fe, Cu and Pb and anions like Cl, SO4 and NO3. Atomic absorption spectroscopy has been used for the estimation of cations and ion-chromatography for anions. Near the coastal regions only up to 40% of the total mass collected could be accounted by these ions whereas in the open sea including ITCZ region 50-70% of the mass could be quantified. On an average <126>13% of total particulate concentration is contributed by <126>6% by nitrates. The mass concentration of sulphate varies from 0.4 to 7.2 μg m^-3 and that of nitrates from 0.1 to 3.7 μg m^-3. Ionic concentrations of Fe, K, SO4 and NO3 which are mostly of continental/crustal origin decrease significantly in the southern hemispheric oceanic regions. Na and Cl are found to be more abundant in the southern latitudes compared to coastal region. In the mid Arabian Sea where the concentration of sulphates and nitrates was observed to be high, the wind was directed from north-eastern regions of central Indian and West Asian regions. Major continental contributions like carbon, silicates and organic components..

3 illus, 3 tables, 11 ref

003457   Murugavel P;Pawar S D;Kamra A K (NO, Indian Institute of Tropical Meteorology, Pashan, Pune-411 008) : Size-distribution of submicron aerosol particles over the Indian ocean during IFP-99 of INDOEX. Curr Sci 2001, 80(Apr), 123-7.

Size-distributions of particles are sometimes relatively flat from 0.0133 to 0.237 μm when the particle concentrations are low in the southern hemisphere. The transport and accumulation of aerosol particles in the Inter-Tropical Convergence Zone is discussed. The relative abundance of large versus small particles is examined with respect to the variation of surface atmospheric pressure along the route.

8 illus, 15 ref

003456   Mohanty U C;Niyogi D S;Raman S;Sarkar A (Centre for Atmospheric Sciences, Indian Institute of Technology, Hauz Khas, New Delhi-110 016) : Numerical study of the role of land-air-sea interactions for the northeasterly monsoon circulations over Indian ocean during INDOEX. Curr Sci 2001, 80(Apr), 60-8.

A number of numerical experiments were performed for a 2-D domain ranging from 14°N to 16°S centered over 76°E. In the experiments, the influence of land-sea interaction (differential heating), topography (Western Ghats), and the thermal gradients (SST and land surface temperature) on the coastal circulations over Equatorial Indian Ocean were studied. Results indicated a strong land-air-sea interaction and feedback teleconnection between the local and large scale features. Interestingly, the model generated land influence to the order of 1000 km off-shore in the simulation domain, consistent with different observations. Results suggest that the oceanic environment in the northeast monsoon over Arabian sea and the Indian Ocean can display significant diurnal variability and heterogeneity due to topography and surface temperature gradients, and that the local features have interactive feedback on the large scale circulations and transport.

10 illus, 1 table, 17 ref

003455   Maheshkumar R S;Devara P C S;Dani K K;Ernest Raj P (Physical Meteorology and Aerology Division, Indian Institute of Tropical Meteorology, Dr Homi Bhabha Road, Pashan, Pune-411 008) : Optical characteristics of aerosols as inferred from a high spectral resolution radiometric observations over Pune during the INDOEX IFP-99. Curr Sci 2001, 80(Apr), 115-19.

The aerosol optical depths varied between 0.17 and 0.52 during the IFP. The forenoon optical depths were found to be higher than those obtained for the afternoon period. Also, the optical depth range was more during the IFP when compared to the same during the first field phase. The retrieved size distributions showed monomodal throughout the IFP, bimodal during January and March, and power-law type during February. The Junge size exponent v, which is an indicator of size distribution of aerosols, varied between 2.0 and 2.2. The daily variation of aerosol optical depth at 0.55 μm showed an increasing trend during the study period.

6 illus, 8 ref

003454   Madan O P et al (Centre for Atmospheric Sciences, Indian Institute of Technology, New Delhi-110 016) : Important synoptic features during INDOEX IFP-99. Curr Sci 2001, 80(Apr), 30-8.

INDOEX IFP-99 was undertaken as part of the international experiment in the Indian Ocean to take observations pertaining to aerosols, radiation, cloud physics and other related meteorological parameters. The important-aim of the INDOEX was to quantify radiative forcing due to natural and anthropogenic aerosols and their feedback on regional and global climate systems. Since prevailing circulation features transports aerosols, it is essential that important synoptic patterns during the expedition phase, i.e. 20 January to 10 March 1999 be examined. Based on the synoptic features it was noticed that cross equatorial flow in lower levels from western Arabian Sea to southern Indian Ocean was significantly higher than the eastern Arabian Sea. Two cyclonic storms, one in the south Bay of Bengal during 1-3 February and another in the south Indian Ocean during 4-13 March were observed. Significant changes in the cross-equatorial flow in the lower/upper tropospheric levels and ITCZ locations were noticed.

13 illus, 3 ref

003453   Kulshrestha U C;Jain M;Sekar R;Vairamani M; Sarkar A K;Parashar D C (NO, Indian Institute of Chemical Technology, Hyderabad-500 007) : Chemical characteristics and source approtionment of aerosols over Indian ocean during INDOEX-1999. Curr Sci 2001, 80(Apr), 180-5.

During INDOEX IFP-99, the samples of aerosols were collected onboard ORV Sagar Kanya over Indian Ocean along the cruise track, for chemical characterization and identification of dominating sources of aerosols. The concentrations of nss-SO4, nss-Ca, nss-Mg, NO3, K, NH4 and SO2 were observed to be significantly higher before ITCZ in nothern hemisphere than across ITCZ in southern hemisphere. In this study, variation of concentrations of nss-SO4, nss-Ca and nss-K with respect to change in latitude, wind direction, wind speed and relative humidity have been highlighted. North of ITCZ, nss-SO4 varied from 2.20 to 18.31 μg/m³ and south of ITCZ from 0.50 to 2.79 μg/m³ while nss-Ca varied from 0.02 to 0.72 μg/m³ south of ITCZ and from 0.01 to 0.14μg/m³ South of ITCZ. Nss-k ranged 0.09-1.43 μg/m³ and 0.07-0.60 μg/m³ before ITCZ and across ITCZ respectively. nss-Ca and nss-SO4 were contributed mainly by NNW and ENE winds while nss-K was observed to be contributed mainly by SSW and ENE winds. Wind speed greater than 4.5 m/s negatively influenced the concentration of nss-Ca concentrations. Correlation coefficients of nss-SO4 with SO2 (r=0.7) and RH (r=0.5) suggested a significant contribution of nss-SO4 by aqueous phase oxidation of SO2.

5 illus, 2 tables, 9 ref

003452   Krishna Moorthy K;Saha A;Niranjan K (Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram-695 022) : Spatial variation of Aerosol spectral optical depth and columnar water vapour content over the arabian sea and Indian ocean during the IFP of INDOEX. Curr Sci 2001, 80(Apr), 145-50.

Results show occurrence of fairly high values of aerosol optical depths along the West Coast of India. The optical depths decrease gradually as one moves down south, with an e^-1 scaling distance of <126> 1200 to 1300 km. Extremely low (near zero) values are encountered in mid Indian Ocean due south of 10° latitude (i.e. on the south of the ITCZ) followed by a weak increase close to Mauritius. Presence of an extensive region of enhanced aerosol optical depths (which we call the West Asian High) is seen in the mid-Arabian Sea between 5° and 10°N westward of 65°E longitude which is stronger and wider than those seen along the coastal regions of India. This effect is seen at the longest wavelength (1025 nm) also. Variation of columnar water vapour content (W g cm^-2) shows highest values (<62> 3 g cm^-2)) around the equator (<126> 3°N to 5°S extending over the entire longitude region) possibly associated with the ITCZ. Moderately high values are encountered along the coastal regions of India and also close to Mauritius. Compared to these, the North west Arabian Sea (between 5 to 15°N and 60° to 70°E) shows rather dry atmosphere with W <60> 2 g cm^-2, indicating prevalence of drier continental conditions.

6 illus, 17 ref

003451   Jayaram A;Satheesh S K;Mitra A P;Ramanathan V (Physical Research Laboratory, , Navrangpura, Ahmedabad-380 009) : Latitude gradient in aerosol properties across the inter tropical convergence zone : results from the joint Indo-US study onboard Sagar Kanya. Curr Sci 2001, 80(Apr), 128-37.

Results undoubtedly show a large spatial difference in aerosol characteristics between north and south of the ITCZ which could lead to a large asymmetry in aerosol radiative forcing between the two regions.

10 illus, 1 table, 19 ref

003450   Jaya Rao Y;Devara P C S (Physical Meteorology and Aerology Division, Indian Institute of Tropical Meteorology, Pashan, Pune-411 008) : Characterization of aerosols over Indian ocean and Arabian sea during INDOEX IFP-99. Curr Sci 0000, 80(Apr), 120-2.

Aerosol optical depth (AOD) measurements in the spectral range 0.3-1.6 μm have been carried out using a multi-channel solar radiometer onboard ORV Sagar Kanya to understand the interaction between continental and marine aerosols. Experiments have been carried out under clear sky conditions for 22 days during 20 January-12 March 1999 covering the latitude belt between 17°N and 20°S, and longitude belt between 71°E and 59°E, over Indian Ocean and Arabian Sea as part of INDOEX IFP-99. Results show larger particle abundance, close to the Indian coast during forward leg compared to that of return leg of the cruise. AODs, in general, exhibit larger values north of ITCZ compared to that of south of ITCZ. The spatial distribution of AOD at 0.502 μm shows greater values north of ITCZ with significant latitudinal gradient compared to that of south of ITCZ. Aerosol size spectrum, derived from spectral AODs, shows monomodal distribution for both pristine oceanic environment (south of ITCZ) and for polluted environment (north of ITCZ).

5 illus, 1 table, 5 ref

003449   Iyengar G R;Ramesh K J;Paliwal R K;Madan O P (National Centre for Medium Range Weather Forecasting, , INSAT Building Annexe, Mausam Bhavan Complex, Lodi Road, New Delhi-110 003) : Structural characteristics of the inter tropical convergence zone over the equatorial Indian ocean during INDOEX-1999 field phase experiment. Curr Sci 2001, 80(Apr), 18-24.

In an attempt to study the performance evaluation of the global data assimilation and forecasting system (GDAFS) in predicting the enhanced ITCZ activity, the successive day-3 forecasts are utilized to delineate the predictive characteristics associated with the ITCZ over the equatorial Indian Ocean. Further, the assessment of the impact of INDOEX glass sonde data on the analysis circulation over the equatorial western Indian Ocean with regard to the cyclonic circulation formed around 5 February 1999 is attempted. It is found that the operational analyses brings out the active and weak phases of the ITCZ activity over the equatorial Indian Ocean quite well. Further, the successive day-3 forecasts of the GDAFS are found to be reasonably successful in predicting the typical enhancement of the ITCZ activity. Assimilation of the INDOEX glass sonde data for a selected period suggests a general improvement in the description of the cyclonic circulation and its associated characteristics.

7 illus, 4 ref

003448   Hemalatha K A;Geetha P;Yasmin S H;Premalatha V K;Balasubramanian S (Dept of Environmental Sciences, Bharathiar University, Coimbatore) : Two parameter Weibull distribution method for predicting cations in the ground water of Cauvery delta of Tamilnadu. Indian J envir Hlth 2001, 43(3), 83-91.

Two parameter Weibull distribution model was applied to evaluate the quality of ground water collected from 50 wells in four regions (CSB, VSB, RCA, NDA) of Thanjavur district. The data of the cations (Ca, Mg, K, Na) and EC were used to predict the ground water quality. The shape and scale along with mean and percentile were zoned. A hybrid approach of the Weibull distribution model was done to estimate the mean. This hybrid approach may be used to predict and forecast the ground water quality. From the study the cationic parameters in the wells were not uniform which may be attributed to contamination either by surface flow or sea water.

6 illus, 8 tables, 12 ref

003447   Gupta P K et al (National Remote Sensing Agency, , Balanagar, Hyderabad-500 037) : Trace gases and aerosol emissions due to biomass burning at shifting cultivation sites in east Godavari district (Andhra Pradesh) during INDOEX IFP-99. Curr Sci 2001, 80(Apr), 186-96.

The aerosol optical depth in five spectral bands have been found to increase from 0.2-0.5 range to 2.0 during flaming and then came back to the normal range of 0.2-0.5. The maximum density of the aerosol particles over the biomass burning sites is found to be in the range of 0.17-0.33 μm. Comparison of the diurnal variation of the UV-B intensity over the burning sites with the ambient level reveals that there is reduction in the UV-B intensity peak during biomass burning phases. This reduction in UV-B intensity had been found to be 35% and 53% over the two different sites selected. An attempt has been made to deduce the fluctuations in the selective absorption of ozone at 297.5 nm in terms of the variability of UV-B intensity at 297.5 nm. The total atomspheric ozone varied from 256 DU to 270 DU which were in accordance with the values for these latitudes. The relationship between UV-B intensity and aerosol optical depth values suggested a correlation coefficient for ambient level (R²=0.614) and (R²=0.7387, R²=0.588) for the two sites of biomass burning areas.

13 illus, 4 tables, 30 ref

003446   George J P (National Centre for Medium Range Weather Forecasting, , Mausam Bhavan Complex, Lodi Road, New Delhi-110 003) : Shortwave radiative forcing by mineral dust aerosols over Arabian sea : a model study. Curr Sci 2001, 80(Apr), 97-9.

Dust aerosol model was developed and its performance validated against pre-INDOEX measurements. This model was incorporated in the NCMRWF T80 global model. A five-day integration was performed with the assumption that light mineral dust is present over Arabian Sea. Mean shortwave dust forcings were computed from the forecast. In general, at surface, a negative dust forcing was noted. At the top of the atmosphere negative shortwave dust forcing was seen mainly over Arabian Sea, where surface albedo is small, in the clear sky conditions.

4 illus, 14 ref

003445   Ernest Raj P;Devara P C S;Maheshkumar R S; Dani K K;Saha S K (Physical Meteorology and Aerology Division, Indian Institute of Tropical Meteorology, Dr Homi Bhabha Road, Pune-411 008) : Spatio-temporal variations in lidar-derived aerosol concentrations at Pune during INDOEX-IFP. Curr Sci 2001, 80(Apr), 112-14.

Concentrations are observed to be relatively higher at almost all the altitudes above 200 m during January. The average aerosol columnar content in the 50-1100 m altitude range is found to be 272 x 10⁶ cm^-2, which is found to be slightly higher than that observed during the same three-month period of 1998 (which includes INDOEX FFP-98). The difference in the aerosol content/aerosol loading between the two years seems to be related to the local meterological condit ons. Normalized concentration gradients have been computed for the all the days of observations and the nocturnal boundary layer (NBL) heights derived. The results show that the average NBL height during the three-month period is around 250 m. Dispersal of aerosol particulates is found to be restricted close to the surface layers on the days associated with very low NBL heights.

5 illus, 1 table, 10 ref

003444   Duli Chand;Modh K S;Naja M;Venkataramani S; Shyam Lal (Physical Research Laboratory, , Ahmedabad-380 009) : Latitudinal trends in O3 CO, CH4 and SF6 over the Indian ocean during the INDOEX IFP-1999 ship cruise. Curr Sci 2001, 80(Apr), 100-4.

Surface measurements of ozone (O3), carbon monoxide (CO), methane (CH4) and sulfur hexafluoride (SF6) were made over the Arabian Sea and the Indian Ocean during the INDOEX field experiment in January-March 1999 covering the latitude range from 17°N to 20°S. Observations show decreasing trends in all these trace gases from the Indian coastal region to the open Indian Ocean. Ozone with a lifetime of few days, shortest among the species presented here, shows large variations while SF6, which has relatively longer lifetime, shows smaller variations. Ozone also shows clearly the effect of ITCZ and its movement. These observations show higher ozone near the Indian coastal region in January 1999 than in March 1999 and also compared to the observed ozone during the INDOEX-1998 cruise. This is believed to be due to strong anti-cyclonic conditions in January 1999 bringing more polluted air from the Indian continent. A decrease in the latitudinal gradient in CH4 was observed in 1999 compared to that in 1998 in the same region, indicating slower growth rate in 1998-1999 period.

^ssc27 ref

003443   Dasgupta S;De U K (Department of Statistics, St. Xavier's College, Calcutta-700 016) : Markov chain models for pre-monsoon thunderstorm in Calcutta, India. Indian J Radio Space Phys 2001, 30(3), 138-42.

Markov chain models of first, second and third order have been used to provide a probabilistic description of the occurrence of the thunderstorm phenomenon in the pre-monsoon season (March-May) in Calcutta (India), The analysis is based on the relevant data for the 10-year period 1985-94. Use of Akaike's information criterion (AIC) reveals that the Markov chain of the third order is perhaps the model that describes best the phenomenon. This finding is also supported by actual verification of the fact that the Markov chain of third order simulates the observed data best. Besides, the time independent behaviour of the chain has also been studied with the help of the steady state probabilities. The theoretical values of the mean recurrence time for thunderstorm and fair weather days hence obtained are is close agreement with the observed data.

8 tables, 13 ref

003442   Basu S;Paliwal R K;Satyanarayana A N V; Mohanty U C;Lykossov V N;Sam N V (National Centre for Medium Range Weather Forecasting, , Mausam Bhavan Complex, Lodi Road, New Delhi-110 003) : Comparative analysis of the characteristics of the marine boundary layer with GCM and 1-D PBL model simulations using INDOEX IFP-99 data. Curr Sci 2001, 80(Apr), 55-9.

Glass-sonde observations consisting of wind, temperature and relative humidity at different pressure levels that were obtained on board ORV Sagar Kanya cruise #141 (INDOEX IFP-99), during winter monsoon of 1999 were used for the present study. An attempt has been made to compared to simulation of the evolution of the Marine Boundary Layer as obtained from the one-dimensional PBL model of IIT Delhi, having TKE-ε closure scheme with that obtained from the GCM of NCMRWF having first order closure scheme. Simulation of various boundary layer characteristics including surface and upper air has been studied. The model simulations are compared with the available observations. Both the models simulated the vertical profiles reasonably well compared with the observations.

6 illus, 6 ref

003441   Basu S;Das Gupta M (National Centre for Medium Range Weather Forecasting, , Mausam Bhavan Complex, Lodi Road, New Delhi-110 003) : Impact of INDOEX data on the NCMRWF analysis - forecast system and evolution of boundary layer structure during IFP-99. Curr Sci 2001, 80(Apr), 7-11.

Observing process is the most important and expensive component of the forecasting system. Impact studies are means of assessing the value of observing systems in terms of the benefit they deliver to model forecasts, and guide efforts to ensure cost-effective deployment of observations. The INDOEX data from IFP-99 for the period 1-8 February 1999 (two glass-sonde observations per day) were assimilated in the global data assimilation system of NCMRWF. The impact of these observations on the analysis and subsequent forecasts was studied. Various aspects of the boundary layer parameters were studied using the first order closure scheme for PBL that include evolution of vertical profiles of various meteorological parameters, diurnal variation of fluxes, etc. The vertical profiles obtained from the model forecasts were compared with the available observations from INDOEX.

6 illus, 9 ref

003440   Bala Subrahamanyam D;Sen Gupta K;Ravindran S; Krishnan P (Space Physics Laboratory, Vikram Sarabhai Space Centre, , Thiruvananthapuram-695 022) : Sea breeze and land breeze along the west coast of Indian sub-continent over the latitude range 15°N to 8°N during INDOEX IFP-99 (SK-141) cruise. Curr Sci 2001, 80(Apr), 85-8.

Observations made during 21-24 January 1999 (forward leg : latitude 15°N to 8°N; longitude 72.3°E to 76.4°E) when the ship was close to the west coast of India and 5-10 March 1999 (return leg : latitude 15°N to 10°N longitude 71.9°E to 74.8°E) when the ship was further away from the coast were used for the study of the extent of sea/land breeze over the Arabian Sea. Simultaneous observations were made by 30-m meteorological tower located at Thiruvananthapuram, 500 m away from the Arabian Sea coast, and the data have been used to compare the existence of sea land breeze circulations. during the forward leg of the cruise, when the ship was closer to the west coast of India, the time series of wind direction show prominent wind reversal, similar to those observed at Thiruvananthapuram during the same period. But during the return leg, when the ship was away from the coast, the wind direction reversal was absent onboard ship, thereby showing the horizontal extent of the land/sea breeze at the west coast of India.

7 illus, 4 ref

003439   Appu K S et al (Meteorology Facility, TERLS/SHAR, Vikram Sarabhai Space Centre, , ISRO, Thiruvananthapuram-695 022) : Spatial distribution of meteorological parameters around 900 hPa level over the Arabian sea and Indian ocean regions during the IFP-99 of the INDOEX programme as revealed from the constant altitude balloon experiments conducted from Goa. Curr Sci 2001, 80(Apr), 89-96.

During the IFP-99 of the INDOEX programme, an Indo-French joint scientific team conducted 17 constant balloon flights from Goa mainly to study the various features of the continental air mass flow from the Indian subcontinent towards the ITCZ induced by the NE winter circulation and thereby to derive the transportation of the continental aerosols and trace gases to the Indian Ocean regions. Out of the 17 flights, 15 were successful. Data obtained from the Constant Altitude Balloon Experiment are analysed to study the features of the wind fields and thermodynamic parameters of the marine boundary layer at <126> 900 hPa level over the oceanic regions adjoining west-coast of Peninsular India. From the balloon co-ordinates, the instantaneous vector wind as well as its zonal and meridional components are estimated. Also estimated are the ambient air temperature and relative humidity at 30 min interval. These data are examined for the spatial features. Mean wind showed presence of three broad flow channels, from India, Africa and West Asia, that are important in influencing the Arabian Sea environment and provide potential pathways for transport of continental pollutants. Variat ons associated with the MJ oscillations are present in the zonal wind, close to the equator. On several occasions wind showed occurrence of eddies with anticyclonic circulation having temporal scales of one to five days.

9 illus, 2 tables, 19 ref

002399   Virk H S;Walia V (Department of Physics, Guru Nanak Dev University, Amritsar-143 005) : Helium/radon precursory signals of Chamoli earthquake, India. Radiat Measmt 2001, 34(1-6), 379-84.

The Bhagirithi and Alaknanda valleys of Garhwal Himalaya, were rocked, respectively, by two major earthquakes : the Uttarkashi earthquake of magnitude m(b) = 6.5, M-s = 7.0 on October 20, 1991 and the Chamoli earthquake of m(b) = 6.8, M-s = 6.5 on March 29, 1999, during this decade. Both these seismic events are associated with ongoing deformation along the main central thrust of the Himalayas. Helium and radon anomalies on March 24 and March 27, 1999, respectively, were recorded at Palampur which is about 393 km from the Chamoli earthquake epicentre. A He/Rn ratio anomaly was recorded on March 20, 9 days before the Chamoli earthquake. The procursory nature of radon and helium anomalies is a strong indicator of the physical basis of earthquake prediction and a preliminary test for the proposed conceptual He/Rn ratio model.

20 ref

002398   Tripathi J K;Rajamani V (School of Environmental Sciences, Jawaharlal Nehru University, New Delhi-110 067) : In situ maturation of sediments within the wearthering profiles: an evidence from Ree behaviour during weathering of Delhi quartzites. Curr Sci 1999, 76(9), 1255-8.

Orthoquartizites of Delhi Supergroup in Delhi region have low abundance of REE. There is a two-fold enrichment of REE in moderately weathered zones on the quartzites accompanied by increase in the amount of kaolinite. The REE patterns however are nearly identical to those fo the unweathered core quartzite. In the strongly weathered outer zones both kaolinite and REE abundance decrease somewhat relative to the lower weak to moderately weathered zones. The weathering processes here involved are the formation of kaolinite possibly by the breakdown of a few grains of mica and the oxidation of pyrites present in the quartzite. During this process, the REE have been mobilized quantitatively by sulfatebearing solutions without any fractionation. In the process the outermost zones have been made friable with lowered REE abundance. It is possible, that REE and Al depleted top friable zones may have been physically eroded away. Thus, although the REE are mobile in upper zones during weathering processes, they could by quantitatively retained in the lower weathering zones due to clay forming processes resulting in the production of silica-rich, REE depleted mature quartzite by stripping off the uppermost friable sediments of the rinds.

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002397   Thangarajan M (NO, National Geophysical Research Institute, Hyderabad-500 007) : Numerical simulation of Groundwater flow regime in a weathered hard rock aquifer. J Geol Soc India 1999, 53(5), 561-70.

Numerical simulation of groundwater flow regime in weathered hard rock region is a valuable tool to assess the groundwater resources and to understand its hydrodynamics of a basin. One such study was carried out in Bukaleru River basin, a hard rock region in Nalgonda district, Andhra Pradesh, India. Recurring droughts and increased exploitation of groundwater to meet the growing needs of drinking water and irrigation had resulted in the decline of regional groundwater levels, causing deterioration of groundwater quality in the basin. In order to evolve future pumping schemes, a preliminary mathematical model of phreatic aquifer was conceptualised, constructed and calibrated in two stages viz., steady and transient conditions. The calibrated model was then used to predict the aquifer behaviour for the next five years. The model study indicates that the phreatic aquifer can sustain the present withdrawal of 28 x 10⁶ m³/year without further decline of water level. Any additional increase of withdrawal in the shallow aquifer will result in progressive decline of water level, as the average annual dynamic reserve is only about 28 x 10⁶ m³. If the present model is refined and validated through additional field data, then optimal utilisation schemes can be evolved.

002396   Thamban M;Purnachandra Rao V (Post Graduate Department of Geology, Government College Kasaragod, Vidyanagar-671 123) : New stable isotope records of sediment cores from the SE Arabian sea - inferences on the variation in monsoon regime during the late quaternary. Curr Sci 2001, 80(11), 1432-6.

Reconstruct the changes in regional hydrography related to the fluctuations in Indian monsoons during the late Quaternary based on the stable isotope composition of the foraminifers and organic matter in three sediment cores from the upper continental slope of western India. The planktic foraminiferal δ¹⁸O contrast between the Last Glacial Maximum (LGM) and Holocene (Δδ¹⁸O), after correcting for the global `ice effect' is relatively high (0.8-1.0%), suggesting notable changes in the sea surface cooling (<126> 2°C) and an enhanced evaporation (increasing salinity by <126> 2.5 p.s.u.) during the LGM and/or increased precipitation during the early Holocene. The diminished Δδ¹⁸O value of benthic records (<126>1.0%) appears to be a basin-wide phenomenon along the shallow depths of the upper continental slope and is related to the eustatic sea level fluctuations. Carbon isotope composition of the organic matter suggests that primary productivity was the main source of organic carbon along this margin throughout the late Quaternary.

3 illus, 1 table, 35 ref

002395   Thakkar M G;Maurya D M;Rachna Raj;Chamyal L S (Department of Geology, M.S. University of Baroda, Baroda-390 002) : Quaternary Tectonic history and terrain evolution of the area around Bhuj, Mainland Kutch, western India. J Geol Soc India 1999, 53(5), 601-10.

Mainland Kachchh has witnessed several phases of tectonic movements since the formation of Kachch rift. The structural set up of the area is dominated by two fault systems - an E-W fault system which controls the geomorphic configuration and a NNW-SSE to NNE-SSW fault system which displaces the E-W faults. The quaternary deposits of the area, alluvial and colluvial fans, channel deposits and miliolites help in categorising Quaternary tectonic activity into two phases. Reactiation of E-W trending faults during Early Pleistocene led to the present landscape configuration and formation of extensive alluvial and volluvial fans along these faults. The post miliolite phase resulted in movements along transverse faults as evidenced by a very youthful fault scarp morphology and faulting in postmiliolite alluvial sediments along this trend. The mountain front sinuosity values also suggest a younger phase of tectonic activity along the transverse faults. The first order topography and the seismic activity suggest continued tectonic instability of the region.

13 ref

002394   Tewari V C (NO, Wadia Institute of Himalayan Geology, 33, General Mahadeo Singh Road, Dehra Dun-248 001) : Discovery and sedimentology of microstromatolites from Menga limestone (Neoproterozoic/vendian), Upper Subansiri district, Arunachal Pradesh, NE Himalaya, India. Curr Sci 2001, 80(11), 1440-4.

Microstromatolite and filamentous cyanobacteria have been discovered from cherty limestone facies of Menga limestone well exposed along Menga-Mara road section of Upper Subansiri district, Arunachal Pradesh, NE Himalaya, India. The microstromatolites are mm size in dimension and show well-developed cycles of columnar overhanging, enveloping and conical structures in petrographic thin sections. The other characteristic features of microstromatolite facies are fibrous radial fabric, zoned dolomite, recrystallized oolites and intraclasts. These microbial facies suggest that sedimentation is controlled by microbial mats in extensive tidal flat complex where photosynthesis was taking place. The deposition took place mainly in subtidal to intertidal zone and the influx of coarse sediments indicates high-energy intertidal environment.The Menga Limestone is regionally correlated with Dedza Formation in the Arunachal Pradesh. The Bomdila Group with Lower Tenga Formation and Upper Dedza Formation has been correlated with Daling-Buxa Formation of Darjiling and Sikkim Himalaya by earlier workers. A Riphean/Mesoproterozoic age is assigned to these carbonates. The stromatolitic assemblage is characterized by Vendian or Neoproterozoic build-ups of Stratifera and Nucliella only in the present area. The present discovery of Riphean assemblage from the Menga Limestone suggest a Vendian/Terminal Neoproterozic age for the Menga-Dedza/Buxa Dolomite of NE Himalaya.

3 illus, 1 table, 18 ref

002393   Tewari H C;Murty A S N;Prakash Kumar;Sridhar A R (National Geophysical Research Institute, , Hyderabad-500 007) : A tectonic model of the Narmada region. Curr Sci 2001, 80(7), 873-8.

Analysis of the reinterpreted results of the seismic refraction and wide-angle reflection data across Narmada-Son Lineament (NSL) indicates that the upper crustal features to the east and west of the Barwani-Sukta fault are different. To the west of this fault a graben exists under the Deccan volcanics, while to the east of it a north-south horst feature between the Narmada north and south faults divides the region in three distinct zones - north, middle and south. This feature is accompanied by upwarp in the mid-crustal as well as the Moho levels, suggesting deep-seated tectonics. The horst correlates with the gravity low axis of central India and large thickness of high density mafic material is present in the upper crust on both sides of it. The present-day crustal structure of the Narmada region appears to have developed in three major phases of the tectonic activity during the Archaean-Proterozoic, Jurassic-Cretaceous and late Cretaceous.

5 illus, 20 ref

002392   Swamy S N;Kapoor P N (NO, KDM Institute of Petroleum Exploration, ONGC, Dehra Dun) : Source rock palynological model for exploration of fossil fuels in Krishna-Godavari basin. J Geol Soc India 1999, 53(5), 549-60.

Exploration for hydrocarbon depends largely upon intergration of surface and subsurface geological, geophysical and geochemical data. The vast majority of fossil hydrocarbons was formed by the alteration of sedimentary organic matter which originate from a variety of different source materials including aquatic and terrestrial biotas. Better understanding of the petroleum system (which includes source, migration and accumulation) in any basin is necessary for hydrocarbon exploration. Assessment of source rock is based upon parameters like organic matter types, richness of organic matter, maturation and paleoenvironment. The various geochemical and source rock palynological parameters are also considered synergistically to decipher source rock potential sequences in Cretaceous and Pre-Cretaceouse sediments of Krishna-Godavari Basin. Source rock paynological model is prepared for various formations viz. Pennar Shale, Krishna Formation, Golapli Formation, Gaujlapadu Shale, Raghavapuram Shale and Tirupati Sandstone to depict spactial and temporal distribution of source rock facies.

18 ref

002391   Sunmonu L A;Dimri V P (Department of Pure Applied Physics, Ladoke Akintola University of Technology, P.M.B. 4000, Ogbomoso, Nigeria) : Fractal analysis and seismicity of Bengal basin and Tripura fold belt, northeast India. J Geol Soc India 1999, 53(5), 578-92.

Northeast India experienced compressive forces from the Himalayan Arc in the north and the Burmese Arc in the east, which led to the development of a number of seismogenic faults, fractures and lineaments. It is observed that the characteristics of earthquakes occurring on an active fault are closely related to the irregularity of fault geometry. Because of their roguh appearances over many length scales, faults can be conveniently regarded as fractal sets, and their geometrical irregularity can be quaantified using factal dimension. Calculated fractal dimension of the distribution of faults in two tectonic blocks, Bengal basin and Tripura fold belt, in the northeast India. Also found that in the spatial sense the fractal dimension and the seismicity are positively correlated.

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002390   Sulochanan B;Koteeswaran M (Department of Soil and Water Conservation, Tamil Nadu Agricultural University, Coimbatore-641 003) : Prediction of maximum daily rainfall at Ootacamund. Madras agric J 2000, 87(10-12), 597-600.

Maximum daily rainfall data for 30 years (1967-1996) of Ootacamund, Nilgiris, recorded by India Meteorological Department were collected from the Directorate of Statistics, Chennai. Two programs were developed in BASIC for Lognormal and Gumbel distributions. The theroetical values so obtained were in close agreement with the observed data except at the highest rainfall for both the distributions.

1 illus, 2 tables, 2 ref

002389   Subrahmanyam A S;Venkateswarlu K;Murthy K S R;Malleswara Rao M M;Mohana Rao K;Raju Y S N (NO, National Institute of Oceanography, Regional Centre, 176, Lawsons Bay Colony, Visakhapatnam-530 017) : Neotectonism - an offshore evidenced from eastern continental shelf off Visakhapatnam. Curr Sci 1999, 76(9), 1251-5.

It is significat that the epicentre falls in the innershelf off Vizianagaram, where a suite of rocks (Santapalle Rocks) outcrop at a water depth of around 30 m. Bathymetry and magnetic data were collected over this region along closely spaced, coast parallel profiles covering the shelf regions. Observed magnetic anomalies are of short wavelength and high amplitude of the order of 600 to 700 nT. Two-dimensional modelling of these anomalies with conventional as well as inversion methods indicates a severely faulted and folded basement of the order of 1 to 6 km. Three closely spaced river channels (Nagavali, Vamsadhara and Nellimarla) trending NW-SE are associated with the faulted and folded basement. Faulting associated with the Nellimarla river channel extending into the offshore zone may be the possible cause of the tremor. Strong magnetic anomalies, complex basement structure, exposed rock outcrops in the innershelf (20 m) in the vicinity of the epicentre of Vizianagaram earth tremor provide evidence of Neo-tectonic activity in this region. The epicentral region falls in a shallow marine environment ideal for generating a geophysical database for stable continental region earthquakes.

002388   Subbarao M V;Narayana B L;Divakara Rao V; Reddy G L N (NO, National Geophysical Research Institute, Hyderabad-500 007) : Petrogenesis of the protolith for the Tirodi gneiss by A-type granit magmatism: the geochemical evidence. Curr Sci 1999, 76(9), 1258-64.

In the Central Indian region, the Tirodi gneisses occur intimately associated with the Sausar Group metasediments. The protoliths for these gneisses might have originated by rift-related intracontinental felsic A-type (anorogenic) magmatism. The geochemical signatures in them like high Zr + Nb + Y + Ce, Ga/Al, Zr/Ni, Rb/Sr and Y/Sc, are quite similar to the A-type granite characteristics and point to the derivation of the protoliths by the melting of lower crustal dehydrated assemblages at high temperatures attained as a result of possible ponding of basaltic magma/magma underplating. The occurrence of mafic rocks related to subduction zone magmatism and back-arc environment in the vicinity of these gneisses in the Central Indian region attest to such an origin for the protoliths of the Tirodi gneisses.

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002387   Srivastava R K;Singh R K (Department of Geology, Banaras Hindu University, Varanasi-221 005) : Petrology and geochemistry of the late archaean siliceous high-magnesian basalts (SHMB) from Kakllur, southern Bastar Craton, central India. J Geol Soc India 1999, 53(6), 693-704.

Greenschist facies metabasalts showing relict spinifex texture, associated with the Late Archaean Bengpal Group, are well exposed in the Kaklur area, Bastar craton, They are classified as siliceous high-magnesian basalts (SHMB) on the basis of its distinct chemistry, such as high SiO₂ (52.83-54.52 wt%), high MgO (11.40-18.35 wt%), hig Cr, Ni, enriched Rb and K, depleted Nb and Ti, and enriched-LREE patterns, as well as the presence of spinifex texture. Low Al₂O₃/TiO₂ and Sc/Y ratios, high Ti/Zr and Sr/Nd ratios less than chondrite corroborate SHMB nature of these basalts and clearly distinguishes them from komatiites/komatiitic basalts and boninintes. They show close geochemical similarities, particularly in high field strength and rare earth element concentrations, with other well studied Western Australian SHMB. Such SHMB are reported in literature to be derived either from komatiitic magma by crustal contamination through assimilation-fractional crystallization (AFC) processes or from magma generated from the refractory continental lithosphere.

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002386   Srivastava P (National Bureau Soil Survey and Land Use Planning, Division Soil Resea, , Amravati Road, Nagpur-440 010) : Paleoclimatic implications of pedogenic carbonates in Holocene soils of the Gangetic Plains, India. Palaeogeog Palaeoclimet Palaeoecol 2001, 172(3-4), 207-22.

Attempts has been made to reconstruct the Holocene climatic history of the Indo-Gangetic Plains based on micromorphological characteristics and stable isotope composition of calcretes in a soil-chronoassociation between the Ramganga and Rapti rivers. The calcrete from the B2 horizon of older soils (QGH4-QGH5 : 6500-13 500 year BP) consists of septaric and irregularly shaped nodules of dense micrite and diffused needles associated with the illuvial clay pedofeatures. Fabric of the calcretes of older soils show inclusion of soil constituents and precipitation of carbonates in between weathered layers of micas. Formation of this calcrete took place during the pedogenesis in an and to semi-arid climate that also influenced vegetation and C4 type biomass such as Chenopodium and Typha angustata spread in the area. A change to warm and humid phase at 6500 year BP led to dissolution and reprecipitation of the calcretes. This led to the formation of blocky crystals and needles of calcite in voids and coarsening of the fabric in the lower horizons.

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002385   Sreerama Murthy N;Ananda Reddy R;Rao M V R K; Sunder Raj B;Murthy N V S;Vittal Rao K P R (NO, Geological Survey of India, Hyderabad) : New Kimberlite discovery from a structural elucidation of gravity data, Maddur - Narayanpet field, Mahbubnagar district, Andhra Pradesh. J Geophys 1999, 20(1), 3-13.

Regional gravity and magnetic maps are of immense use in identifying the most favourable areas in Kimberlite exploration. The study of gravity linears, second order trends, flexures, terminations and their intersection points is significnt, in that they indicate the zones of density/magnetic susceptibility changes the underlying rocks had undergone due to fracturing, several phases of magmatic episodes, deformation events and intrusive activity etc. Since these form a favourable structural setting for the emplacement of kimberlites, delineation of these features from an appraisal of regional gravity/magnetic maps is the first step in Kimberlite exploration. Regional gravity and magnetic maps are prepared on a 1:50,000 scale in Maddur-Narayanpet Field. Kamusanpalli block is selected for semi-detailed geophysical coverage on the basis of structural information inferred from the regional maps. The significant geophysical indications recorded are ground checked and then resistivity profiling was carriedout to test the individual geophysical anomalies. The methodology thus followed has resulted in the discovery of a `concealed Kimberlite pipe' M-11 of size 60 x 20m (semi-weathered) in Kamusanpalli block. Further petrologica and chemical studies confirmed the geophysical findings.

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002384   Sohoni P S;Malik J N;Merh S S;Karanth R V (Department of Geology, M. S. University of Baroda, Vadodara-390 002) : Active tectonics astride Katrol hill zone, Kutch, Western India. J Geol Soc India 1999, 53(5), 579-86.

Katrol hills occupy the central Kachchh mainland and belong to an area of active tectionism. This area is one to the few seismically and tectonically active areas outside the Himalayan mountain belt. A longitudinal foult flanks the hills to the north (Katrol Hill Fault Scarp) and morphotectonic analysis along this hill range has confirmed that the area has undergone differential tectonic uplift. Various geomorphological criteria viz., mountain fornt sinousity, faceting, facet dissection percentage of 62 fronts of two sub-areas, valley floor to valley height ratios an concavity indices of the streams flowing due north and south of Katrol hills reflect the amount of influence of tectonic activity during Quaternary times. Pattern of seismicity in the area reveals that all the known earthquakes in this region fall more or less in the Katrol Hill Zone running E-W for about 100 km. The warping of quaternary rocks further furnishes field evidence of tectonic activity in post Upper Pleistocene times. Morphometric analysis along with seismic pattern and geological evidence indicate that the Katrol Hill Zone continues to be tectonically active.

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002383   Singh S;Malhotra R;Kumar J;Singh L (Department of Physics, Guru Nanak Dev University, Amritsar-143 005) : Indoor radon measurements in dwellings of Kulu area, Himachal Pradesh, using solid state nuclear track detectors. Radiat Measmt 2001, 34(1-6), 505-8.

Results of radon activity recorded in domestic regions of the Kulu area (Himachal Pradesh, India) known for uranium mineralisation are reported. Time integrated track etch technique has been used for the measurement of indoor radon levels. Bare cellulose nitrate LR-115 type II films have been used as detector in the survey of radon. The calibration constant of 4.8 x 10(2) tracks cm(-2) day(-1) per WL of radon at equilibrium (which corresponds to 12.97 x 10(-2) tracks cm(-2) d(-1) per Bq m(-3)) determined by Subba Ramu has been used to express radon activity in Bq m(-3). In some of the dwellings the levels of radon activity are found to be quite high giving an annual exposure dose that crosses the safety limits set by the International Commission on Radiological Protection (ICRP, Protection against radon-222.

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002382   Singh S;Malhotra R;Kumar J;Singh B;Singh L (Department of Physics, Guru Nanak Dev University, Amritsar-143 005) : Uranium analysis of geological samples, water and plants from Kulu area, Himachal Pradesh, India. Radiat Measmt 2001, 34(1-6), 427-31.

Deals with the measurement of uranium content in soil, rock, water and plant samples collected from some areas of Kulu district, Himachal Pradesh, India. The anomalous uranium values have been observed in soil, rock and plant samples belonging to Balsari village of the area. Uranium concentration in water samples is quite low and is thus safe for drinking. The aim of the work is to explore the possibility of uranium exploration and for the health risk assessment in the area.

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002381   Singh R P;Mishra P K;Birbal Singh (Department of Physics, R B S College, Bichpuri, Agra-283 105) : Anomalous VLF electric field perturbations associated with Chamoli earthquake of March/April 1999. Curr Sci 2001, 80(11), 1416-21.

Employing borehole and terrestrial antennas, Very Low Frequency (VLF) electric field perturbations associated with Chamoli earthquakes which occurred in the month of March and April 1999 have been monitored at Agra station (geographic lat. 27.8°N, long. 78°E). The results show that electric field perturbations started appearing in the form of noise bursts 16 days prior to the occurrence of the main shock on 29 March 1999. In majority of the cases of the noise bursts the effect was observed by borehole antenna only, indicating that the signal propagated through crustal region. This result is interpreted in terms of propagation of signals through conductive channels along Delhi-Haridwar ridge and parallel to them between the source and the observing station.

5 illus, 2 table, 32 ref

002380   Sheth H C;Pande K;Bhutani R (Physics Research Laboratory, Division Earth Science, Solar System & Ge, , Ahmedabad-380 009) : Ar-40-Ar-39 ages of Bombay trachytes evidence for a Palaeocene phase of Deccan volcanism. Geophys Res Lett 2001, 28(18), 3513-16.

Presents Ar-40-Ar-39 ages of 60.4 +/- 0.6 Ma and 61.8 +/- 0.6 Ma (2 sigma) for Deccan Trap trachytes from Manori and Saki Naka, Bombay, situated in the tectonized Panvel flexure zone along the western Indian rifted continental margin. These ages provides clear evidence that (i) these trachytes are of Palaeocene age and therefore substantially younger than the lower part of the main flood basalt sequence exposed in the Western Ghats, which precedes the K-T Boundary in age and (ii) the formation of the Panvel flexure along the west coast must have been subsequent to similar to 60 Ma. Considering early alkaline Deccan rocks previously dated at similar to 68.5 Ma, the total duration of Deccan volcanism was at least similar to 8 MY.

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002379   Sheth H C;Pande K;Bhutani R (Department of Geology and Geophysics, School of Ocean and Earth Scienc, University of Hawaii, Honolulu, HI 96822, USA) : <. Curr Sci 2001, 80(11), 1437-40.

Deccan Trap geology of Bombay (Mumbai) differs from the main Deccan flood basalt province in several ways. Very few geological, geochemical and geochronological studies exist on the Deccan geology of Bombay. The basalt of Gilbert Hill, Andheri occupies a special place in Bombay geology on account of its spectacular columnar jointing, more than 50 m high, and for this has been designated a National Geological Monument by the Geological Survery of India. Obtains an ⁴⁰Ar-³⁹Ar plateau age of 60.5±1.2 Ma (2σ) for the Gilbert Hill basalt, and this basalt can be argued to have erupted considerably later (<126> 6 m.y.) than the lower part of the Western Ghats lava pile, and the total duration of Deccan volcanism as a whole appears to have been at least <126> 8 m.y.

2 illus, 1 table, 24 ref

002378   Sharma A;Rajamani V (Jawaharlal Nehru University, School Environmental Science, , New Delhi-110 067) : Weathering of charnockites and sediment production in the catchment area of the Cauvery River, South India. Sediment Geol 2001, 143(1-2), 169-84.

In the Cauvery catchment area, charnockites are making high hills compared to gneisses. In situ, static weathering of a charnockitic boulder shows lesser extent of chemical weathering relative to that developed into a profile. This difference is seed both in clay mineral composition, their REE patterns and in the A-CN-K and A-CNK-FM triangular plots. Based on the chemical changes relative to Ti, three groups of elements are recognized. Ba, Si, K, Na, Sr, Ca and Mg show increasing depletion as the weathering intensity increases in listed order. Al remained relatively immobile, whereas, Fe followed by Mn, Cr, Ni, REE and P show a variable extent of enrichment with increasing chemical weathering. The sediment occurring on the foothills of the charnockite hills have a very uniform composition and texture without any depositional features. Reworking of these sediments in a first order stream has caused only minor compositional changes by the local segregation of heavy minerals on the channel bed and by the removal of small amount of clay materials as suspended load. The REE pattern of the reworked channel bed sand is nearly identical to that of the channel wall sediments, but with lower (by 25%) abundance. Although the rocks are <62> 2500 Ma and, now located in tropical latitudes and probably had the sediments derived from them are chemically very immature suggest ng their exposure to denudational processes very recently by tectonic uplift.

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002377   Sethna S F;Sethna B S;Kothare P;Rao D R K; Saraf P D;Venkateshwarlu M;Patil S K (Department of Geology, St. Xavier's College, Mumbai-400 001) : A note on palaeomagnetic evidence to show tectonic deformation in the deccan volcanic province of saurashtra, western India. Curr Sci 2001, 80(8), 1067-9.

Long curved dyke with peculiar vertical layering, in the Deccan Volcanic Province of Saurashtra, was palaeomagnetically investigated. Palaeomagnetic measurements clearly indicate that the curved character of the dyke is due to some kind of tectonic drag deformation. Such deformation could have possibly developed in case the Saurashtra Peninsula has moved northwards along the Cambay Basin fault. There is a possibility that the horst in the southern part of Saurashtra may have been originally the continuation of the Satpura horst.

^ssc1 illus, 1 table, 14 ref