011270   Verma S P (NO, Centro de Investigacion en Energia, UNAM, Priv. Xochicalo s/no., Col. Centro, Apartado Postal 34, Temixco, Morelos 62580 Mexico) : Solely extension-related origin of the eastern to west-central Mexican volcanic belt (Mexico) from partial melting inversion model. Curr Sci 2004, 86(5), 713-19.

Southern Mexico presents a unique volcano-tectonic situation on earth where the Mexican volcanic Belt (MVB) - a Miocene to Recent volcanic province - is located. Its origin has been highly controversial because of diversity of opposing hypotheses, varying from a conventional subduction-relationship, through hybrid models, to the other extreme of extensional-relationship or rifting, has been proposed. Results of the partial melting inversion model for geochemical data of basic rocks from the eastern to west-central MVB, which constrain its origin in terms of a pure extensional-relationship from a mantle source unaffected by the subduction of the Cocos plate beneath the North American plate. It the Cocos plate does contribute to the magma genesis in this area, the rocks from the `front-arc', i.e. from closer to the trench, should show a clearer geochemical subduction signal than those from the `back-arc' region, i.e. farther from the trench, which is clearly not observed, confirming a mantle origin for the MVB.

5 illus, 2 tables, 49 ref

011269   Verma I J;Banerjee S K (Agricultural Meterology Div, Meteorological Office, Pune-411 005) : Study on water requirement and available water in the root zone in various growth stages of wheat at Dharwar. Mausam 2004, 55(1), 208-14.

^ssc5 illus, 3 tables, 10 ref

011268   Suresh R (India Meteorological Department, , Chennai-600 001) : On nowcasting wind shear induced turbulence over Chennai air field. Mausam 2004, 55(1), 551-7.

With the newly installed Doppler Weather Radar at Cyclone Detection Radar station, Chennai during October 2001, it has been made possible to analyse the meteorological conditions conducive for the wind shear induced turbulence experienced by the pilots in the approach runway at the time of landing and take-off. The radar has been put into operation w.e.f. 21 February, 2002. Wind shears reported during February - October 2002, have been critically analysed. The three dimensional shear (3DS), a combination of radial, azimuthal and elevation shears, gives a first hand information atleast half an hour before the occurrence of shear induced moderate turbulence when its value exceeds 16 mps/km. The 3 DS of more than 20mps/km is normally associated with turublence experimenced by the pilots. With the availability of sophisticated and vast computing power, it is now possible to delineate the layer at which the shear is active within 3-5 minutes from the receipt of the radar measured volume data by quickly computing elevatin/vertical/radial/azimuthal shear etc. However, to arrive at a meaningful conclusion on the threshold values of shears that are conducive for wind shear induced turbulence and the make use of this information to alert the pilots, feed back from the pilots to build a detailed data base is absolutely inevitable. Monitoring of passage of sea breeze front may also be useful to issue wind shear warnings.

7 illus, 2 tables, 22 ref

011267   Stephen J;Manoj C;Singh S B (NO, National Geophysical Research Institute, Hyderabad-500 007) : Direct inversion scheme for deep resistivity sounding data using artificial neural networks. Proc Indian Acad Sci-Earth Planet Sci 2004, 113(1), 49-66.

Initialization of model parameters is crucial in the conventional 1D inversion of DC electrical data, since a poor guess may result in undesired parameter estimations. Investigates the performance of neural networks in the direct inversion of DC sounding data, without the need of a prior information. Introduces a two-step network approach where first network identifies the curve type, followed by the model parameter estimation using the second network. This approach provides the flexibility to accommodate all the characteristic sounding cure types with a wide range of resistivity and thickness. Realize a three layer feed-forward neural network with fast back propagation learning algorithms performing well. The basic data sets for training and testing were simulated on the basis of available deep resistivity sounding (DRS) data from the crystalline terrains of south India. The optimum network parameters and performance were decided as a function of the testing error convergence with respect to the network training error. On adequate training, the final weights simulate faithfully to recover resistivity and thickness on new data. The small discrepancies noticed, are well within the resolvability of resistivity sounding cure interperetations.

12 illus, 3 tables, 33 ref

011266   Srivinivasulu J;Kulkarni A V (Marine and Water Resources Group, Space Applications Centre, , Ahmedobad-380 015) : Estimation of spectral reflectance of snow from IRS-1D LISS-III sensor over the Himalayan terrain. Proc Indian Acad Sci-Earth Planet Sci 2004, 113(1), 117-28.

5 illus, 4 table, 20 ref

011265   Srivastava A;Jain V K;Dutta H N (School of Environmental Sciences, Jawaharlal Nehru University, New Delhi-110 067) : Surface wind characterization at an antarctic coastal station, Maitri. Mausam 2004, 55(1), 95-102.

Surface winds in the atmosphere of Maitri (70.7°S, 11.7°E) a coastal Indian station have been analysed for the year 1992. Surface winds blow most frequently from the sector 165°±25°. Wind chill factor for the year 1992 shows that chilling is highest during the month of August and lowest during the month of January. Two cases of blizzards one during summer and another during winter have also been studied. Surface winds remained practically from the SE, SEE and SW sector during the blizzards.

8 illus, 13 ref

011264   Sinha-Roy S (NO, Birla Institute of Scientific Research, Statue Circle, Jaipur-302 001) : Antitaxial fibrous bands in differentiated stylolites. J Geol Soc India 2004, 63(4), 387-405.

A model for the origin of the FBs has been proposed. The stylolite formation being a pressure-solution phenomenon, the stylolite seams initially contain supersaturated fluid charges with insoluble residues of clay and opaque minerals. When stress relaxation takes place at the end-stage of stylolite formation, fluid pressure drops, the seam walls collapse due to volume loss and the dilation zones are created at the seam margins. These low pressure dilation zones receive the solute by either advective fluid-flow or diffusive mass-transfer, the fluid having been expelled from the shrinking seam mush. This causes the antitaxial fibre growth. The FBs give useful information of pressure-solution mechanism and fibre growth kinetics in relation to stylolite genesis.

17 illus, 36 ref

011263   Sinha A K;Jha N;Upadhyay R (NO, Birbal Sahni Institute of Palaeobotany, 53 University Road, Lucknow-226 007) : Additional information on palynological dating of Chhongtash formation in eastern Karakoram and its palaeogeographical significance. Curr Sci 2004, 86(5), 719-23.

Palynological studies were carried out on additional samples of marine sedimentary succession of Chhongtash Formation, in eastern Karakoram, India. The study revealed the presence of Lower Gondwana (Early Permian Asselian-Sakmarian) palynomorphs. The characteristic taxa reported in the assemblage include Parasaccites, Plicatipollenites, Coheniasaccites and some striate disaccates, viz. Striatopodocarpites and Faunipollenites. These taxa are definite indicators of the close relationship between Karakoram and Early Permian sequence of the Indian subcontinent. The palynoflora shows typical Gondwana aspect. There is little resemblance with Euromarian or Angara flora. The present finding of Gondwana microfossils from additional samples of the Karakoram further supports the contention that during Early Permian, the Karakoram plate was Peri-Gondwanan and it was not far from the Salt Range.

4 illus, 23 ref

011262   Sarate O S (NO, Birbal Sahni Institute of Palaeobotany, 53, University Road, Lucknow-226 007) : Biopetrological Investigations on the coals of Kosar, Dongargaon and Mahadoli areas, Wardha valley coalfield, Maharashtra. J Geol Soc India 2004, 63(4), 406-14.

The coal sequences concealed below the Deccan Trap in Mahadoli (northwestern part) and in the vicinity of Kosar and Dongargaon areas (Kayar Block) delimiting the western boundary of the Wardha Valley Coalfield, Maharashtra, have been analyzed. A comparative study about their maceral constitution, rank evaluation and depositional environment has also been discussed. The coals in these areas are classified under fusic and mixed type barring the top seam of Dongargaon area containing vitriv type of coal. In general, these coals have attained high volatile bituminous C stage of rank.

6 illus, 4 tables, 6 ref

011261   Samui R P;Dhotre A K;Jadhav S S (Meteorological Office, , Pune-411 005) : Soil heat flux under irrigated, partially irrigated wheat and bare vertisol in relation to varying soil moisture and leaf area index at Pune. Mausam 2004, 55(1), 135-48.

Soil heat flux as a function of moisture content in the drying cycles both under irrigated and partially irrigated wheat and in bare black vertisol was studied to relate temporal changes in soil heat fluxes to changes in leaf area index (LAI), soil water content and meteorological parameters. Moisture content dropped as low as 1 to 5 percent by weight at surface layer and 5 to 10 percent by weight at subsurface layers when irrigation was shut off under partially irrigated plot. The peak weekly mean global, net and reflected radiation during the crop growing season in this semi-arid region goes as high as 655.361 and 179 Wm^-2 respectively in the year 1996-97 and 700, 366 and 137 Wm^-2 respectively during the year 1997-98. Soil temperature at 1430 hours IST ranged from 27 to 40°C at the surface (5.0 cm) layer under irrigated condition. It was 7 to 10°C and 2 to 3°C higher in the surface and subsurface layers respectively under partially irrigated wheat during the drying cycle. The upward soil heat flux ranged from -3.3 to -29.7 Wm^-2 at 0730 hours IST, whereas downward heat flux at 1430 hours IST ranged between 8.4 to 33.9 Wm^-2 under irrigated condition. Under partially irrigated condition it varied from -0.7 to -9.2 Wm^-2 at 0730 hours IST and 6.7 to 24.7 Wm^-2 at 1430 hours IST.

3 illus, 6 tables, 9 ref

011260   Saha K;Saha S (NO, , 4008, Beechwwod Rod, University Park, MD 20782, USA) : On the monsoons of south America part 1. Climatological structure and circulation. Mausam 2004, 55(1), 41-72.

Earth-atmosphere radiation budget analyses as well as conventional meteorological analyses are used to establish a case for a well-developed monsoon circulation over South America operating between a heat source over the continent and a heat sink over the surrounding oceans during the sourthern summer. Evidence is produced to show that the criterion of seasonal reversal is met not only by the wind field but also by the fields of several other variables, such as temperature, isobaric heright, specific humidity and rainfall. Computed meridional-vertical circulations for different seasons appear to suggest that the onset and withdrawal of monsoon over the continent are related to the movement of Hadley and Monsoon circulation cells following the seasonal movement of the heat source. A revised definition of the monsoon is proposed in accordance with the findings of the study.

15 illus, 1 table, 17 ref

011259   Roy Bhowmik S K (India Meteorological Dep, , New Delhi-110 003) : Systematic errors of IMD operational NWP model. Mausam 2004, 55(1), 1-14.

The systematic errors of IMD (India Meteorological Department) limited area model over Indian region using 48 hours forecast fields for winter and summer seasons are examined. The study reveals that the core of the sub tropical westerly jet and tropical easterly jet are well simulated in the zonal component of wind. In case of meridional component of wind significant difference is noticed between forecast and analysis. In the upper tropospheric levels (above 100 hPa) northerlybaises are noticed. Thermal structure of the model exhibits cool bias in middle and lower tropospheric levels over the northern latitudes. The nature of model biases of the geopotential height changes with the season. Model drying over the tropical belt and moistening towards the northern latitudes are found in all the seasons studied.

10 illus, 15 ref

011258   Ravichandran M;Vinayachandran P N;Joseph S; Radhakrishnan K (NO, Indian National Centre for Ocean Information Services, Hyderabad-500 033) : Results from the first agro float deployed by India. Curr Sci 2004, 86(5), 651-9.

Agro is a revolutionary concept in ocean observation system that envisages real-time sampling of the temperature and salinity profiles of the global oceans at an approximate spatial resolution of 300 km, once in ten days. Agro float is an autonomous drifting profiler that pops up and down in the ocean from the surface up to 2000 m, measuring two most important physical properties of the water column, viz. temperature and salinity as a function of pressure (depth). Moreover, it can provide an estimate of currents both at the surface and at the parking depth in near-real time. India is an active participant in the Agro programme and has already deployed 31 out of 150 proposed floats. The data received from the first Agro float deployed by India in the southeastern Arabian Sea has been described. The data demonstrate that the temperature and salinity profiles from Agro floats present possibilities for oceanographic studies and spatial and temporal scales that had been hitherto impossible.

11 illus, 14 ref

011257   Rathore S S;Vijan A R;Singh M P;Prabhu B N; Sahu A (Forward Base Office, Assam Arakan Basin-Tripura, ONGC, , Agartala-799 014) : Isotopic evidence of middle proterozoic magamatism from Bombay high field: implications to crustal evolution of western offshore of India. Proc Indian Acad Sci-Earth Planet Sci 2004, 113(1), 27-36.

Precambrian granitic basement rocks obtained from well BH-36 of Bombay High Field, western offshore of India has been studied both by Rb-Sr and K-Ar dating methods. Seven basement samples chosen from two cores have yielded whole rock Rb-Sr isochron age of 1446±67 Ma with an initial ⁸⁷Sr/⁸⁶Sr ratio of 0.7062±0.0012. This age has been interpreted as the formation/emplacement time of the granite. Two biotite fractions of different grain size separated from a sample CC6B2T have yielded Rb-Sr mineral isochron age of 1385±21 Ma. However, these fractions when studied by K-Ar dating method have yielded slightly higher but mutually consistent ages of 1458±43 Ma and 1465±43 Ma, respectively. Further, two biotites separated from additional sample CC5B9T and CC6B3B have yielded K-Ar ages of 1452±42 Ma and 1425±40 Ma with an overall mean age of 1438±19 Ma. This mean K-Ar age is indistinguishable from whole rock Rb-Sr isochron as well as mineral isochron age within experimental error. The similarity in the whole rock and biotite ages obtained by different isotopic methods suggests that no thermal disturbance has occurred in these rocks after their emplacement/formation around 1450 Ma ago. Provides the evidence for the existence of an important Middle Proterozoic magmatic event around 1400-1450 Ma on the western offshore of India which, hitherto,...

6 illus, 2 tables, 24 ref

011256   Randhir Singh;Vasudevan B G;Pal P K;Joshi P C (Meteorology and Oceanography Group, Space Applications Centre (ISRO), , Ahmedabad-380 015) : Artificial neural network approach for estimation of surface specific humidity and air temperature using multifrequency scanning microwave radiometer. Proc Indian Acad Sci-Earth Planet Sci 2004, 113(1), 89-101.

Microwave sensor MSMR (multifrequency Scanning Microwave Radiometer) data onboard Oceansat-1 was used for retrieval of monthly averages of near surface specific humidity (Q_a) and air temperature (T_a) by means of Artificial Neural Network (ANN). The MSMR measures the microwave radiances in 8 channels at frequencies of 6.6, 10.7, 18 and 21 GHz for both vertical and horizontal polarizations. The artificial neural networks (ANN) technique is employed to find the transfer function relating the imput MSMR observed brightness temperatures and output (Q_a and T_a) parameters. Input data consist of nearly 28 months (June 1999 - September 2001) of monthly averages of MSMR observed brightness temperature and surface marine observations of Q_a and T_a from Compehensive Ocean-Atmosphere Data Set (COADS). The performance of the algorithm is assessed with independent surface marine observations. The results indicate that the combination of MSMR observed brightness temperatures as input parameters provides reasonable estimates of monthly averaged surface parameters. The global root mean square (rms) differences are 1.0°C and 1.1 g kg^-1 for air temperature and surface specific humidity respectively.

10 illus, 2 tables, 15 ref

011255   Rajesh Rao P;Kalyana Sundaram S;Thampi S B; Suresh R;Gupta J P (India Meteorological Dep, , New Delhi-110 003) : An Overview of first Doppler weather radar inducted in the cyclone detection network of India Meteorological Department. Mausam 2004, 55(1), 155-76.

Indian Meteorological Department (IMD) maintains a wide network of radars for the detection and study of severe weather phenomena like cyclones, thunderstorms, gust front etc. and for deriving upper air wind profile. To keep pace with the fast developments in the field of weather radar technology, IMS is gradually replacing its conventional radars with digital radars, a few of them with Doppler capabilities. An S-band Doppler Weather Radar (DWR) has been inducted into India Meterological Department's (IMD) Cyclone Detection Radar (CDR) network recently at Chennai as a replacement to the outlived analogue S-band radar and is declared operational from 21 February 2002. Salient features, both hardware and software, of the radar are discussed.

12 illus, 25 ref

011254   Raj Y E A;Amudha B (Regional meteorological Centre, , Chennai-600 006) : Hydrological an dmeteorological features associated with onset of southwest monsoon over Tamil Nadu. Mausam 2004, 55(1), 89-94.

Simple statistical concept has been advanced to determine the onset dates of southwest monsoon over Tamil Nadu. The normal onset date has been found to be 4th June with a standard deviation of 6 days based on 22 years of data. It has been shown that the feeble increase in rainfall over Tamil Nadu in association with the onset is not sustained subsequently and the rainfall decreases in th esecond half of June. The daily upper air data over Chennai and Karaikal for 10 years have been studied and the change in the temporal profiles of these parameters in response to the monsoon onset over Tamil Nadu has been clearly brought out. Some of the unique features of monthly rainfall distribution of Tamil Nadu vis-a-vis those of other meteorological sub-divisions of India in relation to southwest monosson onset have been discussed.

6 illus, 2 tables, 5 ref

011253   Rai A K;Singh V B (Department of Earth and Planetary Sciences, Allahabad University, Allahabad-211 002) : Late neogene deep sea benthic foraminiferal biostratigraphy of ODP sites 762B and 763A (Exmouth plateau), Eastern Indian Ocean. J Geol Soc India 2004, 63(4), 415-29.

The Pliocene-Pleistocene sections at ODP sites 762B and 763A from the Exmouth Plateau(eastern Indian Ocean) were examined to assess the biostratigraphic significance of the benthic foraminifera. The benthic foraminiferal assemblages at both the sites are characteristics of bathyal depths. Based on the stratigraphic ranges of significant taxa, four benthic foraminiferal biozones have been proposed. The proposed biozones in ascending order are Hofkeruva nitidula Zone(<62>6.6 to ~4.72 Ma); Bioloculina murrhina Zone (~4.72 to ~1.8 Ma); Ceratobulimina pacifica-Stilostomella insecta overlap Zone(~1.8 to ~0.82 Ma) and Ceratobulimina pacifica Zone(~0.82 Ma to Recent). The lower and upper boundaries of the Biloculina pacifica Cushman and Harris respectively. The base of Ceratobulimina pacifica Zone is defined by the last appearance of Stilostomella insecta (Schwager).

18 illus, 32 ref

011252   Qaiyum A (Dep of Physics, A.M.U, Aligarh) : The Sun and its Control of Atmospheric Phenomena. Acta Cienc Indica-Phys 2003, 29(4), 429-42.

Earlier discoveries have shown that relationship exists between solar activity and a large number of meteorological variables. But some variations are small and difficult to detect. Small variations may be due to insufficent changes in solar brightness over a solar cycle. Cycles observed in solar irradiance, temperature, precipitation, lake lever, drought and storm variations are -52, 22, 18.5 22, 13, 11, 9.3, 8 and 7 years. Some of the climate & pacific cycles, and polar stratospheric temperature variations are 7, 5.6 5.3, 3.2, 2.5 and 2.1 years. All are claimed to be solar induced. Power spectrum analysis of regional/subdivisional rainfall has been done. It is found that trends and periodicities in rainfall vary from one location to another. Each region/subdivision may or may not have common cycles. But total cycles observed in the rainfall of regions/subdivision are almost same. Further, most of the cycles and periods found from the rainfall power spectra in each region/subdivision are common to common to solar/geomagnetic cycles suggesting a sun/rainfall relationship. However, correlation coefficient between solar/geomagnetic activity are insignificant that leads to the conclusion that solar/geomagnetic and rainfall connections are unlikely. It is most likely that correlation breakdown and some time sign changes are due to solar forcing beats. Two beat together some times enhance their effects and some times cancel. This may one another out. Other reason may be that rainfall varies naturally over a range of time periods, with some close to 11 years. This random variation some times may lead to a weak correlation. Widespread changes in phase between the cyclic variations and corresponding solar activity cycle also cause confusion.

7ilus, 42 ref

011251   Potdar M B et al (Space Applications Centre, , Ahmedabad-380 015) : Remote sensing of spectral signatures of tropospheric aerosols. Proc Indian Acad Sci-Earth Planet Sci 2004, 113(1), 103-16.

With the launch of the German Aerospace Agency's (DLR) Modular Opto-electronic Scanner (MOS) sensor on board the Indian Remote Sensing satellite (IRS-P3) launched by the Indian Space Research Organization (ISRO) in March 1996, 13 channel multi-spectral data in the range of 408 to 1010 nm at high radiometric resolution, precision, and with narrow spectral bands have been available fora variety of land, atmospheric and oceanic studies. It was found that these data are best for validation of radiative transfer model and the corresponding code developed by one of the authors at Space Applications Centre, ad called ATMRAD (abbreviated for ATMospheric RADiation) Validation of ATMRAD model/code using MOS data and synchronously measured derive relationship between MOS radiances and Aerosol Optical Thickness (AOT). The results show that the model performance is satisfactory and a relationship between the spectral parameters of MOS radiances and aerosol optical thickness can be established. Details of the experiments conducted, database, validation of the ATMRAD model and development of the relationship between AOT and MOS radiance are presented.

7 illus, 7 tables, 27 ref

011250   Nair M V;Selvakumar V;Gopi P K (NO, National Museum Institute, New Delhi-110 001) : Excavation of a unique sailboat at Kadakkarappally, Kerala. Curr Sci 2004, 86(5), 709-12.

Recent archaeological excavations at Kadakkarappally, Kerala have exposed an interesting sailboat in a partly intact condition of the wood, considering the hostile environmental conditions prevailing in India, make this a unique find. The preliminary findings of the excavations are presented.

6 illus, 7 ref

011249   Mohapatra M;Koppar A L;Thulasi Das A (Meteorological Centre, , Bhubaneswar) : Some climatological aspects of thunderstorm activity over Bangalore city. Mausam 2004, 55(1), 184-9.

^ssc4 illus, 2 tables, 15 ref

011248   Mohan M;Tiwari M K (Radio and Atmospheric Science Div, National Physical Laboratory, New Delhi-110 012) : Study of momentum transfers within a vegetation canopy. Proc Indian Acad Sci-Earth Planet Sci 2004, 113(1), 67-72.

Two models have been developed by applying conditions of continuity between the roughness sublayer and the top of vegetation canopy having constant foliae distribution. Massman's cosh-type of wind profile and Albini's exponential wind profile have been used to derive expressions for shear stress, displacement height and roughness length in analytical forms. The computed results compared with those of Massman models (1987, 19997) show similarity with the present models.

10 illus, 11 ref

011247   Mishra D;Dey S;Singh R P (Dep of Civil Engineering, Indian Institute of Technology, Kanpur-208 016) : Emissivity of various geological terrains using IRS P4 MSMR data. J Geol Soc India 2004, 63(4), 453-7.

Detailed analysis of the Multi-frequency Scanning Microwave Radiometer (MSMR) data obtained from IRS P4 Oceansat over different geological terrains of Indian region has been carried out. From the MSMR data, seasonal variations of emissivity over major geological terrains has been studied. The emissivity at 6 GHz frequency shows almost similar behaviour over geological terrains but contrast variations in the emissivity are seen during rainy season compared to the winter and summer seasons, especially in the Indo-Gangetic basin.

^ssc3 illus, 12 ref

011246   Mathankar G;Agrawal G D (M.G.C.G.V., , Chitrakoot, Satna-485 331) : Quantification of atmospheric turbulence close to ground level in Satna region : I. Rainy season. Mausam 2004, 55(1), 123-34.

Micro-meterological variables (Temperatures, wind speed, wind direction and wind direction fluctuations) measured at various elevations on continuous basis throughout the rainy season at 106 m tall ABB (Asea Brown Boveri Ltd., Jurich) - Universal tower, Satna (M.P.) have been analysed to determine the turbulence characteristics of atmosphere through four different approaches (Lapse rate, Ri, σ_θ and Tumer's Table). The study shows that the layer close to ground, up to 60 m is severely constrained in respect of vertical as well as lateral eddies except for a few hours (between 0900 hrs or to 1300-1500 hrs or everyday). The upper layer from 60 m to 106 m was found to be turbulent throughout the day and night period during rainy season. This fact of different apparent behaviour of the two layers is considered to be of significant importance to understanding and modeling of heat and pollutant transport. Also the study indicates that vertical and horizontal components of turbulence need to be treated separately. The former could be based on Lapse Rate, Ri, SODAR or even Tumer's Table, but the latter has to depend on σ_θ.

4 illus, 5 tables, 13 ref

011245   Manohar G K;Kesarkar A P (Space Sciences Dep, University of Pune, Pune-411 007) : Climatology of thunderstorm activity over the Indian region. II. Spatial distribution. Mausam 2004, 55(1), 31-40.

Thunderstoms play important roles in many areas of information about earth-atmosphere relationship. Inspite of this awareness of importance of thunderstorms, it is noted that studies about thunderstorms over India received little attention in the past. Latest (IMD, 1999) climatological monthly data of number of thunderstorm days (Thn), rainy days (Tnr), and rainfall amount (Trr) for 276 Indian observatory stations are analyzed, over 11 geographic regions compising India, to examine relationship between these parameters. Analysis of Thn and Tnr data sets showed that in the premonsoon season major part of India is strongly dominated by frequent and widespread thunderstorms but with occasional rainy days. However, in the monsoon season on account of very large increase in the rainy days over the thunderstorm days, the Thn-Tnr relationship is reversed. The climatological feature of India in the premonsoon season is noted as a characteristic of cumlonimbus regime of continental convection, and the one in the monsoon season is termed as cumulonimbus regime of monsoonal convection. The prominence of monsoonal convective regime is therefore very important in deciding the performance of Indian southwest monsson. The analysis between Trr and Thn was carried out over 11 geographic regions of Indian in the four seasons of the annual period. Results pertaining to monsoon season showed that the contribution of thunderstorms to rainfall is highest among the other three seasons.

3 illus, 2 tables, 20 ref

011244   Kane R P (NO, Instituto Nacional de Pesquisas Espaciais -INPE, Caixa Postal 515, 12245-970 - Sao Jose dos Campos, SP, Brazil) : Precipitation anomalies in the United States associated with a finer classification of El Nino events. Mausam 2004, 55(1), 73-88.

A finer classification of El Nino events is attempted. Each year was examined to check whether it had an El Nino (EN) and or a Southern Oscillation Index SOI minimum (SO) and or warm (W) or cold (C) equatorial eastern Pacific sea surface temperatures (SST). Several years were ENSOW, which were further subdivided into two groups viz. Unambiguous ENSOW where SOI minima and SST maxima were observed in the middle of the calendar year (May-Aug) and Ambiguous ENSOW where these conditions were obtained in the early or late part of the calendar year. Other El Nino events were of the type ENSO; ENW, ENC, EN. Years not having El Nino were of the types SOW, SOC, SO, W, C, the last one (C) containing all Snti-El Nitios or La Ninas. For the all India summer monsoon rainfally, Unambiguous ENSOW were overwhelmingly associated with drought and the cold (C) events with floods. For the rainfall in USA during 1900-90, several regions showed distinct ENSO relationships, but different for different regions. Generally, there were good associations between western USA/Great lakes droughts and ambiguous ENSOW, midwest/central USA floods and unambiguous ENSOW, La Ninas showed effects mostly opposite to those of unambiguous ENSOW, but not always, especially in the far west. For the same region, ENSO effects were often substantial and different (opposite) for the main rainy season and the pre and or post-rainy season. Many other details are also presented.

4 illus, 5 tables, 36 ref

011243   Kale V S;Joshi V U (Geography Dep, University of Pune, Pune-411 007) : Evidence of formation of potholes in bedrock on human timescale: Indrayani river, Pune district, Maharashtra. Curr Sci 2004, 86(5), 723-6.

In resistant substrate, potholes require hundred to thousands of years to form. Reports evidence for the formation of several potholes (0.2-1.0 m in diameter) in about 60 years, within man-made channels and pits carved in bedrock basalt in the channel of the Indrayani river. Although documentary evidence is lacking, available information indicates that the man-made channels and pits were most likely carved in mid-1940s. The evidence demonstrates that even in resistant bedrock, such as basalt, measurable bedrock erosion can take place in a few decades. This finding has enormous implications for improving the understanding of the rates of formation of rocky channels and gorges in large Indian rivers, where the energy levels are higher by several orders on magnitude.

3 illus, 10 ref

011242   Jenamani R K (India Meteorological Department, , New Delhi-110 003) : Comments on "periodicities in the frequency of Indian monsoonal cyclonic disturbances and storms" - Mausam, 54,2 (Apiril 2003). Mausam 2004, 55(1), 189-93.

^ssc3 illus, 15 ref

011241   Jadhav S K;Munoty A A (NO, Indian Institute of Tropical Meteorology, Pune-411 005) : Statistical study of the low pressure systems during summer monsoon season over the Indian region. Mausam 2004, 55(1), 15-30.

The occurrence of a closed low pressure area due to low, depression or cyclonic storm is termed as Low Pressure System (LPS). LPS plays an important role in the distribution of rainfall during the southwest monsoon season. Low produce widespread rainfall as compared to depressions and cyclonic storms which yield concentrated rainfall over a smaller area. The distribution of rainfall depends upon the track and life span of LPS. Most of the LPS formed over the Bay of Bengal travel in northwest direction strengthening the rainfall activities over the large parts of the country. The LPS formed during the monsoon season, June to September for the period 1891-2000 over the region covering India, Pakistan Bangladesh, Bay of Bengal and Arabian Sea are taken into account. The duration of LPS is also studied in terms of LPS Days durign the monsoon season. The statistical analysis of LPS and LPS Days is carried out for the monsoon months and for the monsoon season as a whole, for the period 1891-2000. It is seen the frequency of LPS during any of the monsoon months does not exceed six but three LPS in a month are more common. Total number of LPS during the monsoon season ranges from 9 to 18. In June and July maximum total duration of LPS lies between 10-14 LPS Days while in August and September, it is between 15-19 LPS Days. August is the month having maximum number of LPS.

2 illus, 9 tables, 11 ref

011240   Himabindu D;Ramadass G (Geophysics Dep, Osmania University, Hyderabad) : Structural framework of the region in and around Hyderabad as inferred from satellite image analysis: implications for seismic activity. Mausam 2004, 55(1), 214-18.

^ssc2 illus, 10 ref

011239   Ghose A K;Bhattacharya S N (Meteorological Office, , New Delhi-110 003) : Crustal structure in southern and central West Bengal using deep seismic sounding explosion data. Mausam 2004, 55(1), 177-82.

Deep seismic sounding (SDD) data provides as excellent opportunity to accurately delineate the crustal structure of a given region owing to the fact that the location and origin time of the source (Chemical explosion) are available. India Meteorological Department is carrying out such surveys since early 1970's. Seismic wave velocities in the upper pat of the crust in southern and central West Bengal are estimated from three DSS field surveys conducted during 1987-1990. From the analysis of the data it is noted that the sedimentary layer in the region consists of mainly two layers. The first layer is of thickness 1.25 to 1.49 km with P wave velocity of 2.85 to 2.88 km/s and S-wave velocity of 1.71 to 1.77 km/s. Surface wave data show that near Burdwan, the sedimentary layer includes a thin low velocity layer of thickness 250 m at the top. The thickness of lowest sedimentary layer increases southward from 2.32 km to 3.73 km: in this layer the P-wave velocity is between 3.9 & 4.1 km/s. The sedimentary layers are overlying a granitic layer with P- wave velocity of 5.73 to 5.83 km/s.

7 illus, 1 table, 4 ref

011238   Ganesha Raj K;Nijagunappa R (NO, , NNRMS/EOS, ISRO HQ., Antariksh Bhavan, New BEL Road, Bangalore-560 094) : Major lineaments of Karnataka state and their relation to seismicity: A remote sensing based analysis. J Geol Soc India 2004, 63(4), 430-9.

Major lineaments of Karnataka State with length more than 100 km were mapped using satellite remote sensing data and were correlated with earthquake occurences. The results of the study show that there are 43 major lineaments and 33 earthquake occurences with magnitude above 3 (since 1828) in the State. 23 of these earthquakes were found to be associated with 8 major lineaments. The Mandya-Channapatna-Bangalore lineament, Lakshman Thirtha-KRS-Bangalaore lineament, and Chelur-Kolar-Battipalle lineament are some of the seismically active lineaments identified in the study. Most of the earthquakes are confined to the southern part of the State indicating that south Karnataka is seismically more active. Hence, there is a need to upgrade the seismic zonation of Karanataka especially for areas surrounding Mandya, Bangalore, and Kolar. The earthquakes appear to have occured due to movement along/across faults and warrant detailed study of seismically active lineaments using latest techniques like Global Positioning System(GPS), Satellite Laser Ranging (SLR), Synthetic Aperture Radar (SAR) Interferometry, and Thermal Remote Sensing.

2 illus, 2 tables, 54 ref

011237   Fiky G F;Reddy C D;Tealeb A (NO, National Research Institute of Astronomy and Geophysics, Helwan, Cairo, Egypt) : GPS derived velocity and crustal strain field in the vicinity of Cairo City, Egypt. J Geol Soc India 2004, 63(4), 449-52.

Five years of Global Positioning System (GPS)measurements (1996-2000) are used to derive velocity vectors, strain field and principal components of strain in the velocity of Cairo city, Egypt. Estimated horizontal velocity vectors in ITRF96 are in the range of 20-27 mm/yr with an average of 24mm/yr in N4°±5°W. Least-Squares prediction (LSP) technique is used to estimate the dilatational strains, maximum shear strains, and principal axes of strains. The important features are: (1) dilatational strains show that the northern part of the region is under a compressive strain regime, (2) maximum shear strains show good agreement with the recent crustal activities, (3) principal axes of the strains indicate that the compressional force acting at the convergent plate boundary between the Eurasian and the African plates affect the southern part of the Nile Delta and (4) the principal axes of strains show a good correlation with the S_Hmax directions obtained from earthquake focal mechanisms and bore-hole breakouts.

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011236   Dutta S;Rase D M (Meteorological Office, , Pune-411 005) : Study of different rainfall epochs over major cities of India in summer monsoon season. Mausam 2004, 55(1), 194-6.

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011235   Dutta S;Patel N K (Agricultural Resources Group, Space Application Centre(ISRO), Ahmedabad-380 015) : Yield forecast of rabi groundnut in Orissa state using soil moisture storage model. Mausam 2004, 55(1), 204-7.

^ssc1 illus, 2 tables, 10 ref

011234   Dobhal D P;Gergan J T;Thayyen R J (NO, Wadia Institute of Himalayan Geology, Dehradun-248 001) : Recession and morphogeometrical changes of Dokriani glacier (1962-1995) Garhwal Himalaya, India. Curr Sci 2004, 86(5), 692-6.

Dokriani glacier is one of the well-developed, medium-sized (7.0 km²) valley glaciers of Gangotri group of glaciers in the Garhwal Himalaya. The glacier was originally mapped in 1962-63 and was remapped in 1995 by the Survey of India. The snout, surface area and elevation changes were determined by a comparison of these two topographic maps and fieldwork. The glacier shows rapid frontal recession, substantial thinning at the lower elevation and reduction of glacier area and volume. Between 1962 and 1995, glacier volume is estimated to have been reduced by about 20% and frontal area had vacated by 10%. The study revealed that during the period 1962-1995 the glacier has receded by 550 m with an average rate of 16.6 m/yr. However, the yearly monitoring of snout position of the glacier during 1991-1995 revealed an average rate of recession of 17.4 m/yr and has vacated an area of 3957 m².

6 illus, 3 tables, 17 ref

011233   Devendra Singh;Bhatia R C;Srivastava S K (India Meteorological Dep, , New Delhi-110 003) : Satellite analysis of tropical cyclones using NOAA-16 AMSU measurements over Indian region. Mausam 2004, 55(1), 149-54.

The first Advanced Microwave Sounding Unit (AMSU) was launched aboard NOAA-15 satellite on 13 May 1998. AMSU measurements are now also available from NOAA-16 and NOAA-17 satellites. The AMSU is well suited for the observation of tropical cyclones because the ice clouds that cover tropical cyclones do not significantly affect its measurements. The intensity of three tropical cyclones formed over Bay of Bengal and Arabian Sea in the month of October 1999, May and September 2001 were studied using AMSU measurements. The upper tropospheric warm core thermal anomalies over the tropical cyclone areas wer ecomputed from temperature profiles using the NOAA-15 and NOAA-16 AMSU-A measurements. It has been observed that the magnitude of the warm core temperature anomaly at about 250 hPa was an indicator of the intensity of tropical cyclones in all thre cases. The order of the temperature anomaly was about 6°C in case of super tropical cyclone, 1999 while in other two cases the order of the temperature anomaly were of about 3°C for moderate tropical cyclones, 2001. Therefore, it may be stated that the AMSU data appeared to offer substantial opportunities for improvements in tropical cyclone analysis and forecasting.

5 illus, 8 ref

011232   Devaraju T C;Alapieti T T;Kaukonen R J (Department of Studies in Geology, Karnatak University, Dharwad- 580 003) : Geochemistry of Ultramafic Lenses in the granitoids of the Southeastern flanks of Shimoga Supracrustal Belt (Karnataka) with a note on the distribution of platinum group elements and minerals. J Geol Soc India 2004, 63(4), 371-86.

Reports that Analysis of as many as 27 samples of ultramafites,covering all the important petrographic variations has not revealed either anomalies in the content of Pt and Pd or possible potential of PGE mineralization. Sample from the layered ultramafite body to the east of Rangapura, containing variable proportions of chromite bands, however, have yielded significanlty high Os, Ir, Ru and Rh values(the total of these ranges from 130 to 240 ppb). These samples also contain minute platinum group mineral (PGM) inclusions, mainly in the range of laurite-irarsite and less frequently those corresponding to eralichmanite, osarsite, irasite and bowieite. The PGE mineral inclusions are early formed phase of deep seated crystallization which became entrapped in later crystallized chromite and silicates. The ubiquitous hydrothermal and low-grade metamorphic alterations have not apparenlty caused significant migration of PGE.

10 illus, 7 tables, 30 ref

011231   Deshpande C G;Kamra A K (NO, Indian Institute of Tropical Meteorology, Pune) : Physical properties of aerosols at Maitri, Antarctica. Proc Indian Acad Sci-Earth Planet Sci 2004, 113(1), 1-25.

Measurements of the submicron aerosol size distribution made at the Indian Antarctic station, Maitri (70° 45' S, 11°44'E) From January 10th to February 24th, 1997, are reported. Total aerosol concentrations normally range from 800 to 1200 particles cm^-3 which are typical values for the coastal stations at Antarctica in summer. Aerosol size distributions are generally trimodal and openended with a peak between 75 and 133 nm and two minima at 42 and 420 nm. Size distributions remain almost similar for several hours or even days in absence of any meteorological disturbance. Total aerosol concentration increases by approximately an order of magnitude whenever a low pressure system passes over the station. Based on the evolution of aerosol size-distributions during such aerosol enhancement periods, three types of cases have been identified. The nucleation mode in all three cases has been suggested to result from the photochemical conversion of the DMS emissions transported either by the marine air or by the air from the ice-melt regions around Maitri. Subsidence of midtropspheric air during the weakening of radiative inversion is suggested as a possible source of the nucleation mode particles in the third case. Growth of the nucleation mode particles by condensation, coagulation and/or by cloud processes has been suggested to be responsible for other modes in size distributions.

14 illus, 1 table, 46 ref

011230   Das N;Bose M;De U K (Environmental Science Programme, Jadavpur University, Kolkata-700 032) : Identification of a surface layer structure and analysis of humidity data in two weather situations at Jodhpur (26°18'N, 73°04'E), India, durin MONTBLEX 1990. Proc Indian Acad Sci-Earth Planet Sci 2004, 113(1), 73-87.

The Monsoon Trough Boundary Layer Experiment held in 1990 was a multi-institutional effort to probe the atmospheric boundary layer over the monsoon trough over northern India. For this experiment, four micrometeorological towers were set up at four different locations along the normal position of the trough. One such tower of 30m height was located at Jodhpur (26°18'N, 73°04'E), Rajasthan. The fast and slow response data available during the experiment have been used in the present study to determine a suitable layer-structure of the surface layer for evaluation of sensible heat flux using the multilayer hypothesis of Kramm (1989).

5 illus, 6 tables, 12 ref

011229   Chaudhuri S;Chattopadhyay S (Atomspheric Sciences Sep, University of Calcutta, Kolkata-700 009) : Consequences of pre-monsoon thunderstorm - a fuzzy logic approach. Mausam 2004, 55(1), 119-22.

Pre-monsoon thunderstorms are important as well as devastating weather events occurring over Gangetic West Bengal (GWB). The Prime aim is to introduce the concept of Fuzzy Loic to view the consequences of some inportant parameters during the occurrence of severe thunderstorms. The result reveals that fall in surface temperature as well as rise in relative humidity and pressure are the most important consequences during the occurrence of severe thunderstorms. The result further indicates that colossal fall in temperature and massive rise in pressure are the most desirable combination for the occurrence of such storms. The result discloses that when high wind speed is associated with sharp change in relative humidity and air-pressure, the possibility of occurrence of such weather hazards is more. The important finding of the study suggests that, for prediction of the wind speed associated with severe thunderstorms, multiple regressions, using relative humidity and air pressure as predictor, needs to be investigated.

2 illus, 1 table, 11 ref

011228   Bhattacharya S;Kar R (Geological Studies Unit, Indian Statitical Institute, 203 B.T. Road, Kolkata-700 108) : Alkaline intrusion in a granulite ensemble in the eastern ghats belt, India: shear zone pathway and a pull-apart structure. Proc Indian Acad Sci-Earth Planet Sci 2004, 113(1), 37-48.

The alkaline complex of Koraput, Orissa, India, is one of serveral bodies in the high-grade eastern Ghats belt, but this one is an integral part of the high-grade belt and remote from the western boundary against the Bastar craton. The Koraput complex forms a lozenge-shaped intrusion into the metapelitic granulites and is bounded by shear zones. The combined effect of movement along these shear zones, is a northeasterly elongated sygmoidal cavity with maximum width along the northwesterly trending Reidel shear. Thus the Koraput alkaline complex can be considered to have been emplaced in a pull-apart structure, developed in the ramulitic country rocks. Moreover, in view of the fact that the western margin of the high-grade Eastern Ghats belt bears clear evidence of collisional features, rather than that of rifting or brak-up, the rift-valley model for the alkaline magmatism in this high-grade belt appears untenable.

7 illus, 1 table, 24 ref

011227   Basu G C;Goldar R N (Regional Meteorological Centre, , Kolkata-700 027) : Study of catastorphe flood in September 2000 over gangetic West Bengal by a rational method of rainfall - runoff. Mausam 2004, 55(1), 197-204.

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011226   Baruah P K (Department of Applied Geology, Dibrugarh University, Dibrugarh-786 004) : Provenance and depositional environment of eastern Himalayan Gondwana rocks of Siang district, Arunachal Pradesh. J Geol Soc India 2004, 63(4), 440-8.

The Gondwana sequence of West Siang district, Arunachal Pradesh may be subdivided into three units namely diamicitite, black shale and sandstone-shale heterolithic facies in ascending order. In the sandstone-shale alternating unit, the sand facies gradually thickens upwards, in which the lenses and pockets of coal are local in extent. With low quartz to feldspar plus rock fragment ratio (<62>8), the sandstones are mineralogically immature. Matrix dominantly consists of clay and silt-sized quartz which accounts for 11% on average. The chief authigenic constituents found are muscovite, sericite, quartz and iron oxide. Fine to medium grained, poorly to moderately sorted sandstones exhibit moderately intense compaction. The sediments under humid climatic conditions were derived from the uplifted cratonic block comprising dominantly igneous and metamorphic rocks, and subordinately from the vaneer of sedimentary rocks. Sediments were introduced in the basin under cold glacio-marine conditions and progressively passed through tranquill deep marine euxinic environment to lower shore face shelf environment.

7 illus, 2 tables, 26 ref

011225   Barik S K;Jena J K;Janaki Ram K (NO, Central Institute of Freshwater Aquaculture, Kausalyaganga, Bhubaneswar-751 002) : CaCO₃ crystallisation in primary culture of mantle epithelial cells of freshwater pearl mussel. Curr Sci 2004, 86(5), 730-4.

The foundation of natural pearl formation by molluscs is calcium carbonate in the form of argaonite crystals, secreted essentially by the epithelial cells of mantle tissue as nacre. The in vitro explant culture of nacre-secreting pallial mantle explants of Lamellidens marginalis was attempted and vital steps to accomplish this included depuration of pearl mussels with different physical and chemical agents to eradicate various commensal flora and fauna removal of pallial mantle ribbon, aseptic preparation of explants from the ribbon and transfer of those explants into tissue-culture petri dishes. Special, synthetic tissue-culture media enriched with additives, viz. inactivated calf foetal serum and antibiotics were poured into plates with explants. The culture plates were incubated in a carbon dioxide incubator at 5% CO₂ and at 30°C. After 12 h epithelial-like cells began to migrate out and they formed a complete cell sheet surrounding the explant within 7-10 days. Most importantly, cells in the culture indicated functional viability, as subsequently after 38-40 days of culture typical aragonitic crystals of CaCO₃ could be observed throughout the culture plates.

2 illus, 22 ref

010171   Venugopal K;Akut P V;Panvalkar G A;Ramteke R S;Ghosh N (CW&PRS, , Pune-411 024) : Assessment of yield of radial collector well in Banas river bed, Rajasthan. J appl Hydrol 2003, 16(3), 10-16.

A zinc plant of Hindustan Zinc Ltd., (HZL) at Rampura, Bhilwara Dist. Rajasthan has been using sub-surface water resources available in the Banas riverbed through a radial collector well since 1991. The water level in the well has got depleted by 3 m in the first decade of inception of well. For meeting the increased demand of water for the next phase of expansion of the plant, the yield of well in 1991 was required to be estimated. Four different methods viz Recuperation Test, Well design parameters, Recovery test and Determining aquifer parameters by curve matching technique were used. Yield values of 4.72 mgpd, 4.66 mgpd, 4.31 mgpd and 4.80 mgpd have been obtained from these methods respectively. Measures for enhancing the yield of the well were also suggested.

2 illus, 6 ref

010170   Venkateswara Rao N;Hema Malini B;Nageswara Rao K (Geo Engng Dep, Andhra Univ, Visakhapatnam) : Groundwater quality in the changing urban and industrial environment of Visakhapatnam city. J appl Hydrol 2003, 16(3), 46-51.

Analysis of groundwater samples collected from about 125 locations in Visakhapatnam city area revealed varying trends in the groundwater quality in different parts of the city. The locations along the coastal zone - designated as Zone 1 - appear to be facing seawater intrusion into the aquifer as indicated by higher levels of total dissolved solids, especially chlorides in certain pockets along Beach Road, Harbour and Old Town areas. On the other hand, groundwater in the southwestern parts of the city, where a number of industries such as oil refinery, zinc smelter, etc., are located, appears to be contaminated by industrial effluents as indicated by the concentration levels of hardness, sulphates and TDS. However, in Zone 3, i.e., the foothill areas of the city, which are away from the coastline as well as the industries, the groundwater is almost free from any pollution. On the whole, human activities of urbanization (concretization) and industrialisation seem to be responsible for the deteriorating groundwater quality in Visakhapatnam city.

2 illus, 1 table, 19 ref

010169   Sudhishri S;Patnaik U S;Mohapatra N (Central Soil and Water Conservation Res and Training Inst Res Center, , PB No. 12, Sunabeda, Koraput-763 002) : Rainfall - runoff modeling for upper Kolab catchment of Orissa. J appl Hydrol 2003, 16(3), 5-9.

Indiscriminate deforestation and shifting cultivation is causing severe soil erosion and ultimately reducing the storage capacity of Upper Kolab reservoir at a fast rate. So the study for development of rainfall-runoff modeling was conducted in this catchment for better planning and management. Six stations were chosen for the study and Thiessen polygon method was used for finding out the average rainfall. Monthly rainfall and runoff data from 1992-2000 were used and the models were developed for annual, pre-monsoon, monsoon and post-monsoon seasons. The best fit models were found to have high correlation coefficient significant at 5% level and Ramsers' runoff coefficient for the catchment is 0.59.

2 illus, 2 tables, 7 ref

010168   Sinha Ray S P (NO, , ) : Isotope studies of groundwater in arsenic affected areas of West Bengal. J appl Hydrol 2003, 16(4), 36-9.

3 ref