018271   Tripathi K C;Rai S;Pandey A C;Das I M L (K. Banerjee Centre of Atmospheric and Ocean Studies, University of Allahabad, Allahabad-211 002, Email: avinashcpandey@rediffmail.com) : Southern Indian Ocean SST indices as early predictors of Indian summer monsoon. Indian J Mar Sci 2008, 37(1), 70-6.

Four indices of quarterly mean sea surface temperature (SST) values extracted for Southern Indian Ocean (SIO) region for which the maximum correlation with All India Rainfall Index (AIRI) was found with a lag up to 7 seasons w.r.t. the onset of monsoon. The Artificial Neural Network (ANN) technique has been used to study the predictability of the Indian summer monsoon with four indices individually as well as in various combinations. It has been found that two combinations of SST indices of SIO region, SIOI + ACCI and CSIOI + NWAI + SIOI + ACCI, show best predictive skill when used collectively. It has been found that the performance of the ANN model is better than the corresponding regression model in the prediction of ISMR indicating that the relationship between ISMR and SST indices are non-linear in nature.

018270   Tripathi K C;Das I M L (K. Banerjee Centre of Atmospheric and Ocean Studies, University of Allahabad, Allahabad-211 002, Email: drimldas@yahoo.com) : Simulation of Antarctic sea ice area with artificial neural network. Indian J Mar Sci 2008, 37(1), 77-85.

The artificial neural network (ANN) has been used for simulation of Antarctic sea ice area anomalies. Various dominant cycles present in the data have been identified using the Fourier analysis. It has been found that the data of the Antarctic sea ice area has two dominant cycles: annual and half yearly. The effect of the presence and / or absence of these dominant cycles on the simulation results have been carried out. ANN can simulate the broad trend of the sea ice area anomalies when all the cycles are present. However, the prediction skill of model for intraseasonal variability degrades as we remove the trends. Further, the forecast have been verified on the basis of various attributes of the forecast.

018269   Srinivas P;Sarala C (Civil Engineering Dep, K.L. College of Engineering, Vaddeswaram-522 007) : Hydrological data analysis for the identification of droughts in Anantapur ditrict, Andhra Pradesh. Nat Envir Pollut Technol 2007, 6(4), 565-72.

Agricultural productivity, especially in dry land agriculture, depends upon chiefly the occurrence and distribution of rainfall in a particular region, but due to non-uniform distribution of rainfall and prolonged dry spells during monsoon season and crop period, the dry land agriculture in arid and semiarid regions is becoming difficult. The identification of dry spells and wet spells to find out drought occurring conditions are complex because of the fact that, it requires to analyse the vast hydrological data in a systematic order. The laborious process can be made easy with the advent of using computers and the appropriate data management software. Anantapur is one of the drought-affected districts in Andhra Pradesh due to its location in the rain shadow region of Western Ghats. Due to prolonged dry spells and ill distributed rainfall the district underwent a metamorphosis from drought to desert prone area. Keeping this in view, the study has been carried out to identify the droughts in Anantapur district by analysing the daily rainfall and evaporation data for a period of 21 years from 1979 to 2000 by the application of Data Base Management System (DBMS) approach by developing programs using Microsoft Visual FoxPro Software. From the data analysis, dry days, dry spells, wet days, wet spells, monthly, seasonal and annual rainfall, and driest and wettest months were obtained. From the results it is possible to identify the likelihood of occurrence of dry spells and wet spells. The onset of monsoons was late and consequently the late sowing of crops which results in crop failure in Anantapur district. Thus, knowledge of likelihood of occurrence of dry spells will greatly help in protection of crop from wilting. The identification of dry spells is, therefore, helpful in agricultural planning, reservoir operations, releasing of water to canals for irrigation and for planning cloud seeding operations.

2 tables, 10 ref

018268   Singh M M;Mandal S K (NO, Central Inst of mining and Fuel Res, Dhanbad) : Mechanics of rock breakage by blasting and its applications in blasting design. J Mines Metals Fuels 2007, 55(6-7), 183-9.

The process of rock fragmentation involves both gaseous and shock wave energy action but the latter is more effective at smaller burdens. Fragmentation and toe problems were generally encountered in massive rocks for a burden height ratio greater than 0.3. These problems were not observed in closely jointed rocks even when the ratio was as high as 0.5. A ratio of less than 0.2 did not cause backbreak and may be applicable in smooth blasting operations to produce stable ultimate excavation face. Fragmentation and toe problems can be minimized by adopting a reduced burden (less than 0.3 times the bench height) and a larger spacing (greater than 1.5 times the burden).

4 illus, 2 tables, 26 ref

018267   Senthilkumar B;Purvaja R;Ramesh R (Institute for Ocean Management, Anna University, Chennai-600 025) : Seasonal and tidal dynamics of nutrients and chlorophyll a in a tropical mangrove estuary, southeast coast of India. Indian J Mar Sci 2008, 37(2), 132-40.

Seasonal and tidal dynamics of dissolved nutrients (NH₄-N, NO₃+NO₂-N, PO₄-P and DOC), chlorophyll a, and primary production was studied in Pichavaram mangroves, Southeast coast of India. Seasonal changes showed an increase in salinity after tsunami (Pre-Tsunami; 24±4.61, Post-Tsunami; 31±2.35) due to the opening of sand bar at Coleroon River mouth causing an influx of seawater into the mangrove region at flood flow. However, dissolved nutrients showed no marked changes after tsunami and followed the seasonal pattern as observed prior to the event. There is an in situ regeneration of nutrients as a primary nutrient source rather than riverine input during a major part of the year. The nutrient balance of the Pichavaram mangroves was influenced by the tidal cycle. This is indicated by the changes in tidal height, salinity, inorganic nutrients, DOC and chlorophyll a over a 24 hours diurnal survey in both wet and dry seasons. The main features of the low tidewater were high concentrations of the nutrients showed the effects of tidal pumping mechanism. The tidal range were high after the December 2004 tsunami (Tidal range: Pre tsunami; 69±4.7, Post tsunami 126±11.8). It did not causes significant changes in the chemistry of the mangrove surrounding water column.

018266   Sarangi R K;Nayak S;Panigrahy R C (Marine and Earth Sciences Group, Remote Sensing Applications Area, Space Applications Center (ISRO), Ahmedabad-380 015, Email: sarangi@sac.isro.gov.in) : Monthly variability of chlorophyll and associated physical parameters in the southwest Bay of Bengal water using remote sensing data. Indian J Mar Sci 2008, 37(3), 256-66.

Carries out analysis of surface chlorophyll-a concentration in the seas around India obtained using the Indian Remote Sensing satellite IRS-P4 Ocean Colour Monitor (OCM) data. The focus was given to southwest Bay of Bengal where such studies are scanty. The study portraits the chlorophyll-a pattern during July 1999-June 2000. The monthly sea surface temperature (SST) trend and wind patterns using NOAA-NCEP and Quickscat Scatterometer data, respectively, were studied, to elucidate their impact on chlorophyll distribution. This helped to decipher how the reversing monsoon wind induces algal blooming in the surface waters of the study area. Several features like eddies, algal blooms and coastal plumes were observed. Highest mean chlorophyll was observed in January (northeast monsoon) and lowest in May (summer inter monsoon). Adjacent Arabian Sea water found predominantly productive than the Bay of Bengal water. Higher wind speed around 10 m/s in southwest and northeast monsoon shows about two fold increase in chlorophyll concentration to 1.0-2.0 mg/m³ and the SST has shown gradient and decrease of about 1-2°C in the BoB and off southern India, respectively.

018265   Rathore S S;Bhandari S (Mining Engng, M.P. Univ of Agric and Technol, Udaipur-313 001) : Damage assessment in splittable limestone blocks by laboratory scale blast design. J Mines Metals Fuels 2007, 55(6-7), 165-71.

The splittable limestone is extracted in the form of blocks and is cut in the sized slabs for good application in construction/flooring. The uneven shape and crushed aggregate form of limestone is mainly the waste material and has little use. Thus, the recovery in the form of intact blocks and damage control the chief objectives, while extracting these blocks. To this end, laboratory scale studies were carried out for blast damage assessment in splittable limestone blocks. Samples of the splitted limestone blocks were extracted at quarry site for the laboratory scale blasting and testing purpose. The laboratory scale blasts were carried out for quantification of damages. Ultrasonic p-wave velocity was determined for damage detection. [n this study, damages were observed in the limestone block which were largely eliminated and controlled by use of proper liners along the walls of the blastholes.

6 illus, 6 tables, 16 ref

018264   Rai S;Pandey A C;Tripathi K C;Dwivedi S (K. Banerjee Centre of Atmospheric and Ocean Studies, University of Allahabad, Allahabad-211 002, Email: avinashcapndey@rediffmail.com) : Predictive skill of DEMETER models for wind prediction over southern subtropical Indian Ocean. Indian J Mar Sci 2008, 37(1), 62-9.

The ensemble mean prediction of winds at 850 hPa from individual models of DEMETER project has been compared from NCEP observation over southern subtropical Indian Ocean during summer monsoon season (JJAS) for the time domain 1980-2001. Predictability of U850 hPa (U850) and V850 hPa (V850) has been tested by different statistical approach like root mean square error (RMSE) for the region between Madagascar and western Australia in view of the importance of this region in anomalous variation of south central African rainfall variability as evidenced by some recent studies. A dichotomous forecast skill measure has been performed by calculating predictive skill measures like accuracy, bias, probability of detection (POD), false alarm ration (FAR), probability of false detection (POFD), threat score (TS), equivalent threat score (ETS) and Heidke skill score (HSS) for model produced U850 and V850 from all the individual models and multi model ensemble (MME). It has been found that the root mean square error has been reduced by applying MME but there is no effect on dichotomous predictive skill measures.

018263   Rai S;Khare N;Pandey A C (K. Banerjee Centre of Atmospheric and Ocean Studies, University of Allahabad, Allahabad-211 002, Email: avinashcpandey@rediffmail.com) : Antarctica sea ice variability and southeast Indian Ocean SST: Possible relationship. Indian J Mar Sci 2008, 37(1), 35-9.

Relationships between the Antarctic sea ice variability and extrapolar climate variables especially the Indian Ocean SST have been explored and we have identified that the southeast Indian Ocean SST shows the most persistence relationship with Antarctic sea ice variability. The SST is the unique precursor for the Australian summer monsoon, Indian summer monsoon and ENSO phenomenon after the 1976-1977 regime shift and is also linked with recently discovered Indian Ocean Dipole event of subtropical Indian Ocean.

018262   Prasanna M V;Chidambaram S;Vasu K;Shahul Hameed A;Unnikrishna Warrier C;Srinivasamoorthy K;Anandhan P;John Peter A (Earth Sciences Dep, Annamalai University, Annamalai Nagar-608 002) : Identification of the geochemical processes in coastal groundwater using hydrogeochemical and isotopic data: a Case study of the Gadilam river basin in southern India. Indian J Mar Sci 2008, 37(2), 200-6.

The Gadilam river basin in Tamilnadu is characterized by different geological formation viz. Archaean, Cretaceous, Tertiary to Recent Alluvium and groundwater serves as the major source for domestic, agriculture and other water-related activities. Forty four groundwater samples were collected during summer and post monsoon. Twenty three samples were analysed for stable isotopes (δ¹⁸O and δD). Geochemical signatures of groundwater were used to identify the chemical processes that control hydrogeochemsitry. Chemical parameters of groundwater such as pH, EC, TDS, Na⁺, K⁺, Ca⁺, Mg⁺, HCO₃-, SO₄-, PO₄- and H₄SiO₄ were determined. Interpretation of hydrogeochemical data ascribes that secondary leaching, saline water intrusion and anthropogenic impact in this regime. Interpretation of δ¹⁸O and δD indicates recharge from the meteoric water in Tertiary aquifer and from evaporated water in Alluvium aquifer.

018261   Pant V;Deshpande C G;Kamra A K (NO, Indian Institute of Tropical Meteorology, Dr. Homi Bhabha Road, Pashan, Pune-411 008, Email: kamra@tropmet.res.in) : Size distributions of aerosols over the Indian Ocean. Indian J Mar Sci 2008, 37(1), 104-8.

Concentration and size distribution of aerosol particles in the size range of 0.5 to 20.0 μm were measured over the Indian Ocean during January 23 to March 31, 2004. Total aerosol concentration showed the North-to-South positive gradient with latitude over the Indian Ocean North of the Inter Tropical Convergence Zone (ITCZ). Minimum concentration of aerosols was observed immediately South of the ITCZ and it increased on either side of the ITCZ. Contrary to being monomodal in shape in this size range as is generally expected over open ocean, the aerosol size distributions followed the Junge's power law and show the transport of aerosols from the Indian subcontinent to North of the ITCZ, even though several hundreds of kilometers away from the Indian coastline. Aerosols South of the ITCZ exhibited monomodal size distributions which were typical of marine aerosols in the pristine environments. Aerosol size distributions in the roaring forties clearly showed the generation of sea-salt particles due to the wave breaking activity in this region of high winds. Abundance of particles of <60> 1.0 μm diameter dominated over the Indian Ocean North of the ITCZ.

018260   Pandey A C;Rai S;Mishra A P (K. Banerjee Centre of Atmospheric and Ocean Studies, University of Allahabad, Allahabad-211 002, Email: avinashcpandey@rediffmail.com) : Anomalous variation of sea surface height in Southwestern Indian Ocean. Indian J Mar Sci 2008, 37(1), 40-6.

Model produced sea surface height anomalies (SSHA) are compared with Topex/Posiedon altimetry observation for the region 65° 15' S to 30° 45' S and 29° 15' E to 120° 45' E covering the Indian Ocean. Some resemblance was found between model and observation except for Agulhas return current system region. The interannual variability of the sea surface temperature anomaly (SSTA) and SSHA have been studied using 24 years model run data for the domain given above. This analysis demonstrates high correlation between SSTA and SSHA as evidenced by observational studies using altimetry data. Sea surface height variability in Southern Indian Ocean (SIO) is much higher compared to other parts of the Indian Ocean. Negative dipole mode event of Indian Ocean Dipole (IOD) was found in mode 2 of Empirical Orthogonal Function (EOF) analysis.

018259   Pandey A C;Rai S (K. Banerjee Centre of Atmospheric and Ocean Studies, University of Allahabad, Allahabad-211 002, Email: avinashcpandey@rediffmail.com) : Sensitivity of the Indian Ocean circulation to surface wind stress. Indian J Mar Sci 2008, 37(1), 55-61.

There is a lot of debate on the responses of Antarctic Circumpolar Current (ACC) in relations to changes in Southern Hemisphere winds and how the momentum input by the surface wind stress can be transferred down to the ocean floor. An σ coordinate Ocean General Circulation model was used in the present study. The major circulations in the Southern as well as tropical Indian Ocean have been discussed. The sensitivity of model with respect to wind stress forcing has been performed by using the surface wind stress climatological data of Hellerman and daSilva for the Indian Ocean up to 60°S. It has been found that the response of zonal wind stress over tropical Indian Ocean north of 5°S was large. The response of change in surface wind stress was negligible in the Southern Indian Ocean.

018258   Luis A J;Ravindra R (Polar Remote Sensing Div, National Centre for Antarctic and Ocean Research, Ministry of Earth Sc, Headland Sada, Goa-403 804, Email: alvluis@ncaor.org) : QuikSCAT-based momentum flux analysis over the Southern Ocean. Indian J Mar Sci 2008, 37(1), 47-54.

Using QuikSCAT vector winds, the seasonal and interannual variability of momentum flux were studied to explore the underlining dynamics for its modulation over the Southern Ocean (SO) during August 1999 to July 2003. The wind speed validation of ship and QuikSCAT measurements in the western Indian sector of the SO showed a bias and root mean square error of 0.3 and 1.6 m/s, respectively. On seasonal time scales, the spatial wind stress patterns reveal a basin-wide variability and the boreal summer monsoon significantly influencing it in the Indian Ocean (IO) sector. The temporal march of the momentum flux for different ocean sectors exhibit a seasonal cycle with a maximum range between 0.13 and 0.18 N/m² during August-September and a minimum range between 0.07 and 0.11 N/m² during December - January, with a temporal shift of ±1 month between the sectors. The atmospheric pressure gradient between tropics and high latitudes enhances the momentum flux in the IO sector during austral winter. On interannual time scales the momentum flux maps indicate a marked regional variability which is highest in IO sector and an evolution of cyclonic circulation south of 50°S during austral winter. Based on earlier studies and after a detailed examination of SST and wind stress curl fields, it is argued that orientation of the SST gradient relative to direction of wind stress drive an atmospheric response through wind stress curl and divergence modulations, which in turn dictates the intensity of momentum flux on seasonal time scales.

018257   Lal R P (NO, India Meteorological Department, Mausam Bhawan, Lodhi Road, New Delhi-110 003, Email: lalrp@yahoo.com) : Meteorology of Southern Ocean in Lazarev Sea area as revealed from observations obtained from Indian Antarctic Expeditions. Indian J Mar Sci 2008, 37(1), 93-8.

Ship observations taken during voyage through Southern Ocean and observations recorded at Indian Antarctic Station Dakshin Gangotri (DG), have been used to study the latitudinal and diurnal variations of air temperature and sea surface temperature (SST) and climatology of Lazarev Sea area. Air temperature and SST are highly correlated and the SST lags by 1.5 °C during summer and the degree of lag reduces as winter approaches. The meteorological surface observations show an annual mean surface pressure of about 985 hPa. Surface wind is mainly easterly with annual average mean wind speed of 17 Kn. The annual average air temperature is -16.6 °C with a highest average air temperature of -2.5°C during January and lowest average air temperature of -28.1°C during August. Highest maximum temperature of 9.9°C and lowest minimum temperature of -52.0°C has been reported from coastal station. Diurnal variations of SST and air temperature have been observed in Lazarev sea area. It was not feasible to visualize these variations on moving ship.

018256   Jain S L (Radio & Atmospheric Sciences Div, National Physical Laboratory, CSIR, New Delhi-110 012, Email: sljain@nplindia.ernet.in) : Measurement of column ozone, water vapour over Indian Ocean. Indian J Mar Sci 2008, 37(1), 99-103.

The study of various minor constituents in the atmosphere plays an important role in the understanding of physics, chemistry, dynamics and radiation budget of the atmosphere. These trace species have temporal as well as spatial variation and therefore the knowledge of latitudinal distribution of these species is of great significance. Keeping this in view a highly sophisticated and microprocessor based compact sun photometer consisting of five filter channels at 300, 305, 312, 940 and 1020 nm was used to measure column ozone, water vapour in addition to various other parameters such as UV-B radiation, near IR radiation, aerosol optical depth etc. The measurements were made from Goa, India (15° 24' N, 73° 42' E) to Maitri, Antarctica ( 70° 46' S, 11° 45' E) over Indian Ocean during 16th Indian Scientific Expedition to Antarctica (December 1996-March 1997). It was found that water vapour decreased while total ozone increased as the ship moved towards the coldest, the windiest and the largest icy continent i.e. Antarctica.

018255   Huang B;Shukla J (Climate Dynamics Dep, College of Science, , George Mason University, Email: huangb@cola.iges.org) : Interannual variability of the South Indian Ocean in observations and a coupled model. Indian J Mar Sci 2008, 37(1), 13-34.

The mean state, annual cycle, and interannual variability of the coupled ocean-atmosphere in the South Indian Ocean produced by a 300-year simulation of a coupled ocean-atmosphere general circulation model (CGCM) are compared with those from 51-year (1950-2000) observational datasets. The CGCM simulates realistically the mean annual cycles for both the sea surface temperature (SST) and lower atmospheric circulation, including the seasonal positions of the 10oC and 20oC SST isotherms, the zonal and meridional migration of the South Indian Ocean subtropical high, and the fluctuation of the southeast trade winds and mid-latitude westerly winds. Interannually, the dominant model anomalous SST pattern in austral summer and fall showed some similarities to the observed Indian Ocean subtropical dipole mode, featuring opposite SST anomalies between the northeastern ocean to the west of Australia and the southern ocean. The model pattern is different from the observed one in its overly zonal spatial structure. Both the model and observed anomalous events are generated in response to atmospheric perturbations over the subtropical and mid-latitude South Indian Ocean that disturb the subtropical high during austral spring and summer. The corresponding wind speed changes of the trade winds and westerly modulate the surface heat flux into the ocean and generate SST anomalies, which usually persist into austral fall and in turn modify the lower atmospheric circulation in the subtropical Indian Ocean, especially the areas near Madagascar in the fall season. In the observations, the initial extratropical atmospheric fluctuations are significantly correlated to the global tropical variations associated with El Nino/Southern Oscillation. They are more strongly linked to the southern annular mode in the model.

018254   Gopalakrishna K;Shabi B;Mahesh Bilwa L (PG Department of Applied Geology, M.E.S. Ponnani College, University of Calicut, Kerala-679 586, , Email: gkgeo@rediffmail.com) : Distribution of ostracode assemblages along the nearshore and offshore areas of Malabar coast, Kerala (west coast of India). Indian J Mar Sci 2008, 37(3), 298-306.

Sixty-one ostracode species have been identified in 76 sediment samples from 28 nearshore and 48 offshore locations off Malabar Coast, Kerala. Q mode cluster analysis of the ostracode assemblages of the nearshore sediments indicates that the entire nearshore assemblages can be classified into two clusters - cluster I - Kumbla (A₁) - Hosdurg (B₁) and Mattul (D₁) blocks and Cluster II - Payyannur (C₁) - Cannanore (E₁) - Telicherry (F₁) blocks. This clustering is probably due to the differences in the depositional environment. The influence of estuarine environment is predominant in the cluster I due to the mixing of freshwater from the surrounding land masses. Several backwaters are observed in the areas covered by this cluster. Cluster analysis of offshore assemblages indicate that the entire offshore off Malabar coast can be divided into two clusters, cluster I - Kumbla (A₂) and Bekal (B₂), cluster II - Neeleswaram (C₂), Payyannur (D₂) and Payangoti (E₂) blocks. The presence of shallow water ostracode species in cluster I which lived in nearshore sand and silty sand substrate under the influence of subtropical water currents are inferred and further indicated by the fossil molluscan assemblages. Q-mode cluster analysis and details of physical and ecological parameters suggest that there is a substantial influence of substrate, organic matter and salinity in the distribution, diversity and abundance of the ostracode. Based on this, the Malabar coast of Kerala is significantly classified as a marine ecosystem/environment category.

018253   Das I M L;Mitra A (K. Banerjee Centre of Atmospheric and Ocean Studies, University of Allahabad, Allahabad-211 002, Email: profimldas@yahoo.com) : In-situ data and NCEP reanalysis: a comparative study in the Southern Ocean and Antarctic Ocean. Indian J Mar Sci 2008, 37(1), 86-92.

Special expedition was launched by the National Center for Antarctic and Ocean Research (NCAOR), India on board R/V Akademik Boris Petrov during 25 January to 1 April 2006 passing the Southern Ocean and reaching the Larsemann Hills area of East Antarctica. The surface layer in-situ data generated from the cruise are compared with that obtained from the NCEP reanalysis during the same period along the track of the vessel. It is concluded that the NCEP reanalysis sea surface temperature and air temperature have some discrepancies as the vessel enters the sea ice zone near the Antarctic coast. The air pressure is well modeled but the relative humidity shows high variability throughout the period of the study. The wind speed is poorly correlated with that obtained from the NCEP due to the use of "Course over the ground" in place of ship "heading" while calculating the true wind.

018252   Chudaeva V A;Chudaev O V;Yurchenko S G; Sugimory K;Matsuo M;Kuno A (NO, Pacific Institute of Geography, Vladivostok, Russia, Email: valchud@hotmail.com) : Composition of groundwaters of Muraviov-Amursky Peninsula, Primorye, Russia. Indian J Mar Sci 2008, 37(2), 193-9.

Seawater intrusion, composition and quality of the shallow ground water in the south of Primorye region had been investigated. The Muraviov-Amursky peninsula is a middle mountain area (up to 400 m). The rocks in this area are presented by Permian volcanic, sedimentary, and granite rocks as well as Triassic sediments. Water had been included in a fracturated zone. The water table is located at depths ranging from less than 1 meter to more 20 m. The changes is depending on seasonal and atmospheric precipitation that varies between 1000-1200 mm/y. Values of pH ranging from 5.4-8.4, main ions composition is mixed with HCO₃-Ca, Na - in granite rocks. Sea water intrusions had been examined by chemical and stable isotopes data.

018251   Chudaev O;Chudaeva V;Sugimon K;Kuno A;Matsuo M (NO, Far East Geological Institute, FEB RAS, Vladivostok, Russia) : Composition and origin of modern hydrothermal systems of the Kuril island arc. Indian J Mar Sci 2008, 37(2), 166-80.

The study consists the original geochemical data on the thermal waters of the Kuril Islands (Mendeleev, Golovnin, and Ebeko volcanoes) and relation between thermal waters and ore formation. Among the thermal water types three main groups can be distinguished: sodium-chloride, acid sulfate and chloride-sulfate-bicarbonate. The contents and behaviors of siderophile, chalcophile, lithophile, and rare-earth elements are discussed. These data, together with the result of isotopic studies, enumerates the origin of these waters. The high-temperature sodium-chloride waters have a profound effect on the formation of copper-pyrite mineralization on Mendeleev, Ebeko and Baransky volcanoes. The acid waters influence the processes of hypergenic ore formation.

018250   Chidambaram S;Ramanathan A L;Prasanna M V; Lognatan D;Badri Narayanan T S;Srinivasamoorthy K;Anandhan P (Earth Sciences Dep, Annamalai University, Annamalai Nagar, Tamilnadu) : Study on the impact of tsunami on shallow groundwater from Portnova to Pumpuhar, using geoelectrical technique - south east coast of India. Indian J Mar Sci 2008, 37(2), 121-31.

Andaman - Sumatra tsunami has caused distress to humanity and natural environment. Damage on the natural system has to be assessed scientifically for sustainable development. Geoelectrical studies are the realistic approach for comparing behavior of aquifer before and after tsunami. A study has been conducted on a shallow aquifer in the coastal region to assess salinity variation due to the impact of tsunami. Significant variations were observed in apparent resistivity values, due to percolation of sea water into shallow aquifers. Transformation of curve types has been noted in few regions in various aquifer depths. Changes in the formation resistivity and formation factor have also been noticed, which indicate salinity increase in aquifers. Geoelectrical cross section of the aquifer shows that perched water lens identified has also been affected by tsunami stress.

018249   Bala Krishna Prasad M;Ramanathan A L (Earth System Sciences Interdisciplinary Center, University of Maryland, College Park, Maryland 20740, USA) : Dissolved organic nutrients in the Pichavaram mangrove waters of east coast of India. Indian J Mar Sci 2008, 37(2), 141-5.

Spatial and temporal analytical measurements of organic nutrients were made in the Pichavaram mangrove ecosystem (south east coast of India) to understand the dissolved organic nutrient dynamics. Monthly measurements of physical parameters and dissolved organic nutrients were made at several locations at daytime during low tides. High concentrations of DOC and DON were found in monsoon and DOP in summer. The distribution and dynamics of dissolved organic matter have been regulated by the monsoonal fresh water discharge from the adjacent sources. However, the microbial mineralization induced by summer temperature regulates the nutrient biogeochemical processes and also control the biological productivity. In general, the mangrove ecosystem supplies considerable loads of nutrients to the oceans than the river systems and regulate the global nutrient biogeochemical cycles.

018248   Azarmsa S A (Faculty of Marine Sciences, Tarbiat Modares University, Gisha Bridge, P. O. Box: 14115-111, Tehran, I.R. Iran, Email: azarmsaa@modares.ac.ir) : Thermal structure in coastal waters of central Bushehr (Iran/Persian Gulf). Indian J Mar Sci 2008, 37(3), 273-8.

Thermal structure was studied in the northern coastal part of the Persian Gulf in Iranian southern province of Bushehr. Temperature measurements revealed that the morning-afternoon temperature variations were in the range of 0.2 - 4°C at deeper layers and 0.2 - 1.7°C near the sea surface. The range of the morning-afternoon temperature variations was also time dependent and reduced from a maximum value of 4°C in August to its minimum value of 0.2°C in November. Monthly average of the seawater temperature decreased about 7.4°C in the temperature decreasing period of August to November; with the maximum thermal gradient of about 3.8°C / month occurred in transition from October to November. Cross shore distribution of the sea surface temperature was almost constant. Moreover, both the maximum (36.8°C observed in August) and minimum (26.5°C observed in November) water temperatures were recorded at the surface layer, indicating that the temperature field in the study area is mainly affected by the air-sea heat fluxes. Water column was not thermally stratified at shallow waters (h <60> 24 m). In November, intense heat losses at the air-sea interface cause the water column become well mixed in the study area and thus, thermal stratification disappeared even at deeper waters.

018247   Asa Rani L;Suresh Babu D S (NO, Centre for Earth Science Studies, Akkulam, Thiruvananthapuram-695 031) : Statistical evaluation of ground water chemistry from the west coast of Tamil Nadu, India. Indian J Mar Sci 2008, 37(2), 186-92.

Ground water chemistry in the coastal area between Kollamkode and Kanyakumari has been studied. Quality assessment was made through the estimation of pH, EC, salinity, DO, Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl-, SO₄^2-, PO₄^3-, NO₃-, NO₂-, HCO₃-, and total hardness. The wells in general showed high values of conductivity, salinity, chloride, hardness and calcium. The chemical relationship exhibited by Piper's diagram suggests that the groundwater mainly belongs to the hydrochemical facies Na-Ca and Cl-SO₄-HCO₃. Samples from the coastal fringe zone seldom represent fresh groundwater. Seasonal landward shift of freshwater-saltwater interface was observed throughout the coastal zone. It was found that Na⁺ and Cl^- are the dominant cation and anion in the area. Correlation analysis showed perfect correlation between EC and TDS, reveals that EC is a measure of dissolved solids in ground water. The clusters defined by Q-mode analysis reflect the spatial distribution of samples and the R-mode cluster conveys that salinity, TDS, EC and Na⁺ form one group. The interface zone that extends up to 200-250m from the shoreline has to be carefully exploited, after identifying the discharge and the probable zones.

018246   Ansari A R;Hariharan R;Sivaprasad S (NO, Neyveli Lignite Corporation Ltd., Neyveli, Email: ansari.ar@nlcindia.com) : Groundwater managemtn in Neyveli basin. J Mines Metals Fuels 2007, 55(4), 114-24.

8 illus, 3 table

017245   Vikas Kumar;Vohra A;Srivastava V (NO, Asia-Pacific Institute of Management, Jasola, Sarita Vihar, New Delhi-110 025, Email: vohra64@gmail.com) : Nickel and iron as attenuator materials for helix TWT. Indian J Radio Space Phys 2007, 36(4), 345-47.

Coating of lossy material is done on the helix support rods to absorb reflections in a helix travelling wave tube. Carbon is a very commonly-used material used for this type of coating, but other materials may also be employed for this purpose. Coatings of carbon, nickel and iron have been done and evaluated for the attenuation performance at microwave frequencies. Three alumina rods have been coated with different methods to characterize them for attenuation. One alumina rod has been coated with carbon using the pyrolytic deposition method, while two others have been coated with iron and nickel using the electro-deposition method. An experimental set-up involving a narrow-height waveguide with a hole was used to measure the attenuation of the coated rods at 6.0 GHz frequency.

017244   Suryanarayana Rao K N (NO, ISRO Satellite Centre, Airport Road, Bangalore 560-017) : GAGAN - The Indian satellite based augmentation system. Indian J Radio Space Phys 2007, 36(4), 293-302.

Global Positioning System (GPS) from the USA, Global Navigation Satellite System (GLONASS) from the Russian Federation and the proposed GALILEO satellite navigation system from Europe are meant for providing position and timing information for a variety of applications. However, for Safety Critical applications the basic constellations cannot meet the requirements in terms of accuracy, integrity and availability. For this purpose, the basic constellations are augmented by an overlay system. Indian Space Research Organization (ISRO), along with Airport Authority of India (AAI) is implementing the Satellite Based Augmentation System (SBAS) for the Indian region. The project called GAGAN (GPS Aided Geo Augmented Navigation) has a full complement of the SBAS inclusive of ground and onboard segment. The first phase of GAGAN is nearing completion. Deals with the basic SBAS concept, GAGAN configuration, implementation and the challenges involved. The roadmap towards the final operational phase is also indicated.

017243   Sultana Q;Sunehra D;Venkata Ratnam D; Somasekhar Rao P V D;Sarma A D (Research and Training Unit for Navigational Electronics, Osmania University, Hyderabad-500 007, Email: ad_sarma@yahoo.com) : Significance of instrumental biases and dilution of precision in the context of GAGAN. Indian J Radio Space Phys 2007, 36(5), 405-10.

The positional accuracy of the GPS Aided GEO Augmented Navigation (GAGAN) system is basically dependent on ranging errors and the satellite constellation geometry. This paper focuses on enhancing the performance of the system through the estimation of instrumental biases and augmentation of GAGAN using pseudolites (pseudo-satellites). The line-of-sight ionospheric measurements derived from the Global Positioning System (GPS) observables are corrupted by the instrumental biases present in both the GPS satellites and the receivers. The instrumental bias and Total Electron Content (TEC) results (Hyderabad GAGAN station (78.47°E, 17.45°N)) obtained using the Kalman filter technique are presented. It is found that the estimated biases are almost stable during the observation period and show close proximity with other reported values in the open literature. For some strategic applications further augmentation of GAGAN with pseudolites is necessary. Five configurations comprising GPS/geostationary satellites and pseudolites are considered for optimizing the Dilution of Precision (DOP). It is found that the pseudolite-system with properly located pseudolites can augment GAGAN and improves the positional accuracy of the user.

017242   Sohu D;Sharma J D;Jain P (Reproductive Physiology and Environment Toxicology Lab,Zoology Dep, Univ of Rajasthan, Jaipur-302 004) : Groundwater quality of villages of Sanganer tehsil: Focus on fluoride and fluorosis. J Ecotoxic envir Monit 2007, 17(3), 227-33.

Attempt was made to assess the groundwater quality status of fifty villages of Sanganer Tehsil, Jaipur. A total of two hundred drinking water samples were collected from open wells, tube wells and hand pumps and analyzed for physico-chemical parameters. Physical health of villagers was also studied through personal interrogation. The analytical results indicated significant variations a he analyzed samples with respect to their chemical composition. Majority of samples do not comply with Indian as well as WHO standards for most of the water quality parameters. The fluoride concent n the groundwater of these villages ranged from 0.4 to 6.4 mg/l. Sixty two percent villages were found to be endemic for fluoride causing dental, skeletal and non-skeletal fluorosis among people. Further the villagers were suffering from dental caries, teeth mottling (65.5% ), genu valgum limitations of movements of joints and spine (51.4%), knock-knee syndrome (25.7%), various muscular deformities (28.4% gastrointestinal discomfort (10.1%) as well as neurological manifestations (23.9(37>). Overall water quality was found unsatisfactory for drinking purpose without any prior treatment as high fluoride and EC in drinking water manifest ill effects on human health.

4 tables, 13 ref

017241   Sinha D K;Singh A K (Center of Advanced Study in Geology, Delhi University, Delhi- 110007, Email: devasinha@yahoo.com) : Surface circulation in the eastern Indian Ocean during last 5 million years: Planktic foraminiferal evidences. Indian J Mar Sci 2007, 36(4), 342-50.

Describes the major circulation changes in the eastern Indian Ocean during last 5 million years based on variation in planktic foraminiferal assemblages in various ODP and DSDP cores examined by various workers. The Late Miocene/Pliocene transition is characterized by weakening of the Leeuwin Current and migration of the polar front towards north. The early Pliocene is marked by closing of the Indonesian Seaway for surface waters and strengthening of the Leeuwin Current, a general warming of the surface waters and thickening of the mixed layer in the eastern Indian Ocean. The Late Pliocene and Pleistocene witnessed severe climatic fluctuations and episodic weakening and strengthening of the Leeuwin Current in response to either ENSO induced changes in the Western Pacific Warm Pool or lowering of sea level and reduction in Indonesian throughflow due to ice sheet expansion.

017240   Shyam Lal (NO, Physical Research Labratory, ahmedabad-380 009) : Trace gases over the Indian region. Indian J Radio Space Phys 2007, 36(6), 556-70.

Some of the main results related to atmospheric ozone, related trace gases and aerosols in India are reviewed in this paper. Variability in tropospheric ozone has been observed, while there are no observed changes in the stratospheric ozone. Surface measurements of these species are being carried out by various research groups. Even though pollution levels are higher, surface ozone rarely exceed 100 ppbv in India. Aerosols show large spatial and temporal variability. There is a need for detailed measurements of these trace gases covering different regions in India and vertical distributions in the troposphere. Satellite measurements of these constituents are needed to understand their long range transport.

017239   Sharma V;Bhagyapati Devi L (Geology Dep, University of Delhi, Delhi-110007, Email: vsharma752004@yahoo.co.in) : Neogene oceanographic and climatic changes in the northern Indian Ocean: Evidence from Radiolaria. Indian J Mar Sci 2007, 36(4), 361-8.

Neogene is one of the important periods in the earth's history in view of significant changes that took place during the period in climatic and oceanographic conditions. Radiolarians from well preserved cores, uplifted marine sequences, and surface sediments from the northern Indian Ocean provided opportunity to reconstruct the Neogene oceanographic and climatic events. Studies based on radiolarians from land-based sections revealed episodes of cooling and warming in the late Early Miocene to Middle Miocene. Investigations of radiolarian upwelling fauna in the cores from the western Arabian sea demonstrated strengthening and weakening of upwelling during late Middle Miocene to Recent. Examination of radiolarians from surface sediments suggested presence of Antarctic Bottom water in the Mozambique and Madagascar basins of the western Indian Ocean. Certain radiolarian species are found useful in understanding paleomonsoonal changes and have been used to interpret such changes.

017238   Sengupta N;Glover I A (Institute for Communications & Signal Processing, Electronic & Electri, University of Strathclyde, Royal College Building, 204 George Street,, , Email: ian.glover@eee.strath.ac.uk) : Remote sensing of radio ducts using wind profilers. Indian J Radio Space Phys 2007, 36(5), 383-5.

Case study is presented of refractivity gradient height-profile retrieval using a 915 MHz wind profiler operated by the UK Meteorological Office at Camborne, UK. The retrieved gradient compares well with that obtained from concurrent radiosonde data gathered at the same location, thus demonstrating the potential of such profilers for the investigation of duct dynamics and the collection of unbiased duct statistics.

017237   Saxena S;Kolkar P;Bhamra H S (Zoology Dep, M.M.H. College, Ghaziabad-201 001, Email: saxena_sapna01@yahoo.co.in) : Bio-monitoring of water quality of hindon canal versus river hindon in Uttar Pradesh, India. J expl Zool 2007, 10(2), 429-36.

Water quality assessment of canals has become a subject of concern, ever since the importance of protecting the natural aquatic environment of rivers have been realized for the conservation of fresh waters and also its water quality. The present paper deals with the comparative assessment through biomonitoring of water quality of Hindon canal after its diversion from Hindon river. The average depth, width and flow velocity of Hindon canal increased in compared to river Hindon. However, the substratum composition remained almost similar in both the water bodies. There was significant improvement observed in the physicochemical water quality of Hindon canal compared to river water quality. Similarly, average bacterial load of total coliform and faecal coliform also reduced to a great extent in Hindon canal. Increase in percentage of Molluscs communities and decrease in arthropod taxa of benthic macro-invertebrates in Hindon canal indicated loss of aquatic life due to various hydrological variations in Hindon canal. The Average biological water quality remained moderately polluted class 'C' in both the water bodies.

11 illus, 7 tables, 10 ref

017236   Sarkar S K;Anil Kumar (Radio and Atmospheric Sciences Div, National Physical Laboratory, New Delhi 110 012, , Email: sksarkar@mail.nplindia.ernet.in) : Recent studies on cloud and precipitation phenomena for propagation characteristics over India. Indian J Radio Space Phys 2007, 36(6), 502-13.

Radio propagation above a frequency of 10 GHz is affected by precipitation in terms of attenuation due to its high dielectric constant. As far as Indian subcontinent is concerned, rain and cloud are the most important ones. Thus, there is still tremendous need to develop a strong database on these parameters. The work carried out on cloud and rain characteristics in relation to radio wave propagation over India in recent years only, from 2000 till today is reviewed in this paper. These results are useful to design as well as for estimation performance of microwave communication and for radar propagation over different locations situated in different geographical regions of India.

017235   Rastogi R G (NO, Physical Research Laboratory, Ahmedabad-380 009) : Some aspects of equatorial electrojet in South America. Indian J Radio Space Phys 2007, 36(4), 315-17.

The strength of the equatorial electrojet is shown to be stronger at 75% longitudes than at 45% longitudes inspite of the magnetic field intensity being lower along 45% than 75% longitudes. There was significant correspondence in the day-to-day variation of the daily range as well as in the character of daily variation of the horizontal geomagnetic field, H, at two equatorial electrojet stations separated by 30% in longitude.

017234   Rao V G;Rao S L N;Das U C;Dutta T K; Chakraborty R N (HLS Asia Limited, Delhi, , ) : Reservoir monitoring through wireline logs. J Geophys 2007, 28(3-4), 91-5.

Oil fields of upper Assam have been monitored using Reservoir Monitoring Tool (RMT) of Halliburton. It is based on Carbon / Oxygen ratio principle measured through inelastic mode of interaction between high-energy neutron and nucleus. A supplementary support to this measurement is also provided by the gamma ray spectrum recorded from the capture mode of nuclear reaction. Water saturation values estimated through open hole logs and C/O method (recorded after a time lapse of nearly four years) have been compared which indicate a pretty good match at the top part of oil zone, while in the bottom part, oil seems to have been replaced by water, and OWC moved up by 15m. The original OWC was at 2782m and the present OWC is at 2767m. The perforation interval 2763-2767m is now very close to the water zone which is the reason for higher water cut. Ultrasonic cement evaluation using Halliburton's Circumferential Acoustic Scanning Tool (CAST) also indicated no channeling behind casing.

4 illus, 2 ref

017233   Rao K J;Muralidharan R;Srivastava P K; Desapati T;Chaturvedi A K;Chaki A (Atomic Minerals Directorate for Exploration and Res, , Hyderabad) : On the effective use of integrated study of aerospace data for targeting heavy mineral placers - a case study from Krishna - Godavari coast, Andhra Pradesh, India. J Geophys 2007, 28(3-4), 97-104.

Integrated study of Airborne Gamma Ray Spectrometric (AGRS) and Remote Sensing datasets was carried, out over an area of 25,000 sq. km along the alluvial plains and coast of Andhra Pradesh with an objective to identify potential zones of heavy mineral concentration. Anomalous thorium zones above a threshold of 30 ppm were demarcated from the AGRS data considering the invariable association of monazite with other heavy minerals. Marine and fluvio-deltaic landforms were mapped from satellite image. Integration of the high thorium zones with favourable marine landforms resulted in identifying 36 potential sand bodies with extensions of 1-25 km in length and 1-8 km in width. The delineated sand bodies include the known Kakinada heavy mineral deposit. Ground confirmation and auger hole sampling upto 1.501 depth from twenty-seven potential sand bodies revealed presence of 2-62% Total Heavy Minerals (THM). Besides the known high heavy mineral concentrations along beaches, four new inland placer- rich bodies associated with palaeo-strand lines and rear dunes were also located with THM content ranging from 14-62% at Gudapalli, Nakshatranagar, Chollangipeta, and Pattigondi. The heavy minerals identified mainly are ilmenite followed by pyriboles, sillimanite, garnet, zircon, rutile and monazite. The technique establishes the validity and effective integrated use of AGRS and Remote Sensing to locate favourable heavy mineral placer concentrations.

4 illus, 1 table, 15 ref

017232   Pullen S;Enge P (NO, Stanford University, USA, Email: spullen@stanford.edu) : Overview of GBAS integrity monitoring with a focus on ionospheric spatial anomalies. Indian J Radio Space Phys 2007, 36(4), 249-60.

The Local Area Augmentation System (LAAS) or, more generally, the Ground Based Augmentation System (GBAS), has been developed over the past decade to meet the accuracy, integrity, continuity and availability needs of civil aviation users. The GBAS utilizes a single reference station (with multiple GNSS receivers and antennas) within an airport and provides differential corrections via VHF data broadcast (VDB) within a 50-km region around that airport. Provides an overview of GBAS integrity verification, explaining how integrity risk is allocated to various potential safety threats and how monitors are used to meet these allocations. In order to illustrate GBAS integrity monitoring in detail, this paper examines the potential threat of ionospheric spatial anomalies (e.g., during ionospheric "storms") to GBAS and how GBAS protects users against this threat. In practice, the need to mitigate potential ionospheric anomalies is what dictates CAT I GBAS availability.

017231   Prince P R;Renuka G (Physics Dep, University of Kerala, Thiruvananthapuram-695 581, Email: drprprince@yahoo.com) : Whistler wave instability and plasma sheet ALC distribution at substorm onsets. Indian J Radio Space Phys 2007, 36(4), 318-24.

Whistler waves interacting with an assumed anti-loss cone (ALC) distribution is shown to become highly unstable at times of substorm onsets. This establishes the presence of ALC electrons at onset-time geomagnetosphere plasma sheet (PS). The stability analysis proves that the whistler instability resulting from ALC interactions arises at frequencies greater than the electron cyclotron frequency. The study establishes the role of plasma b as a factor determining the extent of whistler instability even at times of highly disturbed conditions. The major part of free energy available at PS during substorm onsets is proved to be the contribution due to the anisotropy of the ALC distribution function. Presence of a few cold electrons along with hot ALC plasma is shown to cause wave decay.

017230   Ponmanickam P;Rajagopal T;Rajan M K;Achiraman S;Palanivelu K (Animal Science Dep, Bharathidasan Univ, Tiruchirappalli-620 024) : Assessment of drinking waterqualtiy of vembakottai reservoir, Virudhunagar district, Tamil Nadu. J expl Zool 2007, 10(2), 485-8.

Attempt has been made to assess the water quality status of "Vembakottai reservoir" in relation to physicochemical characteristics and its suitability for drinking purpose. The reservoir is located at Vembakottai; Virudhunagar district, Tamilnadu. It was constructed for the supplying drinking water to Sivakasi and its surroundings. The water samples were analyzed for water temperature, transparency, pH, DO, free CO₂, chlorinty, alkalinity, hardness and BOD. The results suggest that water quality of the reservoir is within the permissible limits and the water is suitable for drinking, fish culture and irrigation purposes.

1 table, 18 ref

017229   Perona G;Notarpietro R;Gabella M (NO, Politecnico di Torino, Electronics Dep, Corso Duca degli Abruzzi, 24 - I-10129 Torin, Italy, Email: giovanni.perona@polito.it) : GPS radio occultation on-board the OCEANSAT-2 mission: An Indian (ISRO) - Italian (ASI) collaboration. Indian J Radio Space Phys 2007, 36(5), 386-93.

In the first quarter of 2008, the Indian satellite OCEANSAT-2 will be launched. The Italian Space Agency (ASI) signed a Memorandum of Understandings with the Indian Space Research Organization (ISRO) in which it is agreed to put on-board the OCEANSAT-2 satellite the Italian GNSS receiver devoted to Radio Occultation (ROSA-Radio Occultation Sounder of the Atmosphere). The ROSA receiver has been developed with a new-concept hardware configuration with respect to that normally characterizing a GNSS receiver: it will track the GPS "occulted" signal both just before its setting and just after its rising from the local horizon using an open loop technique, and it will automatically switch from (or to) the standard closed loop approach when the signal crosses higher atmospheric regions. Observations from ROSA will be downloaded both to the Indian and the Italian receiving stations where they will be processed by the ROSA Ground Segment, developed by Italian universities and research centres. In particular, the first version of the processing software will be integrated in a ground segment installed in Matera (Italy) and mirrored at Hyderabad (India). Its second version will be installed in a distributed ground segment implemented by connecting, on a web-based GRID, hardware and software infrastructures installed at the research centres and universities involved in its development.

017228   Paula E R;Kherani E A;Abdu M A;Batista I S; Sobral J H A;Kantor I J;Takahashi H;Rezende L F C;Muella M T A H; Rodrigues F S;Kintner P M;Ledvina B M;Mitchell C;Groves K M (NO, INPE-National Institute for Space Research, Av. dos Astronautas 1758, 12.227-010 Sao Jos‚ dos Campos, Sao Paulo, Brasil) : Characteristics of the ionospheric F-region plasma irregularities over Brazilian longitudinal sector. Indian J Radio Space Phys 2007, 36(4), 268-77.

Based on the data obtained from a network of GPS L1 band receivers deployed in Brazil, are presented here the characteristics of the 400 m ionospheric irregularities during magnetically quiet and disturbed conditions. The network is composed of 12 GPS scintillation monitors and covers the latitudinal region from the magnetic equator up to the southern crest of the Equatorial Ionization Anomaly (EIA), which is characterized by large horizontal gradients in the electron density distribution. Some results on equatorial spread-F statistics obtained from digisonde data over Cachoeira Paulista (22.41° S, 45° W, dip latitude 14.89° S) and from ionosonde data over Tucum n (64.5° W, 27° S, dip latitude 13.71° S) are also used in this work to complement the results from GPS network. The effects of local time, season, latitude, longitude, background ionization, solar cycle and magnetic activity on the ionospheric irregularities are presented. The ionospheric irregularity zonal velocities determined by magnetically east-west spaced GPS receivers are also presented. The influence of the ionospheric irregularities on GPS based navigational systems is discussed. These observations, complemented by computational simulations, may improve our understanding of the factors responsible for the generation, growth and dynamics of the equatorial F-region plasma irregularities.

017227   Pandya M R;Singh R P;Panigrahy S (Agriculture Forestry and Environment Group, Space Applications Centre, ISRO, Ahmedabad-380 015, Gujarat, Email: mrpandya@sac.isro.gov.in) : Directional reflectance of vegetation targets: simulation of its space measurements by coupling atmospheric and biophysical radiative transfer models. Indian J Radio Space Phys 2007, 36(3), 219-28.

Vegetative surfaces are non-lambertian and deriving their spectral properties from space-borne sensors becomes complicated when off-nadir view angles are taken into consideration. In order to utilize off-nadir observations a complete understanding of directional reflectance is needed. This requires understanding of propagation of solar radiation as radiative transfer (RT) problem through a coupled system of vegetation canopy and atmosphere as a function of view angles. In this paper, a new approach of coupling biophysical (PROSAIL) and atmospheric (6S-code) RT models has been proposed to simulate at-sensor directional reflectance for vegetation target. At-sensor reflectance was simulated using 6S-code for the viewing geometry pertaining to 0, 5 and 26 deg view angles (hypothetical multispectral sensor with forward and backward viewing capabilities) for varying atmospheric conditions with the lower boundary condition parameterized through vegetation canopy reflectance obtained from PROSAIL model. Sensitivity of directional reflectance to input parameters were inferred at top-of-canopy and top-of-atmosphere level. The degree of anisotropy in reflectance pattern due to directional viewing represented by a parameter called g-factor was quantified (3-24% in red, 2-9% in near-infrared and panchromatic channels at top-of-atmosphere) which depends on wavelength and increases with atmospheric turbidity. This modeling study would help understanding capabilities of future space-borne sensors with directional/multi-spectral imaging.

017226   Oladosu O R;Jegede O O;Sunmonu L A;Adediji A T (Physics Dep, Federal University of Technology, P. M. B. 704, Akure, Nigeria, Email: koladosu@yahoo.com) : Bowen ratio estimation of surface energy fluxes in a humid tropical agricultural site, Ile-Ife, Nigeria. Indian J Radio Space Phys 2007, 36(3), 213-8.

The Bowen ratio energy balance (BREB) is a micrometeorological technique often used for estimating the surface energy fluxes (i.e. latent heat, sensible heat fluxes) because of its simplicity, robustness, and affordability. The same method has been applied in this study to partition the available energy (R_n - G₊) at a humid tropical agricultural site in Ile-Ife, Nigeria (7°33'N, 4°33'E) during the transition period (wet and dry) between 25 and 29 Feb. 2004. Results obtained for the diurnal variations of the energy fluxes in relation to changing surface condition are satisfactory. For the relatively dry days, the sensible heat flux is comparatively of the same magnitude as the latent heat flux except on a day when it was a little higher, but it is less during the wet days. It is therefore obvious from this study that for a tropical weather, evaporation is the next essential factor after radiation in the energy balance due to the prevailing humid conditions in the zone.

017225   Narayana Rao T;Narayana Rao D (NO, National Atmospheric Research Laboratory, Gadanki-517 112) : Wind profiler observations of lower and middle atmospheric processes over Gadanki. Indian J Radio Space Phys 2007, 36(6), 526-42.

National Atmospheric Research Laboratory (NARL), a unique site having Mesosphere Stratosphere Troposphere (MST) Radar, Lower Atmospheric Wind Profiler (LAWP), Lidars, disdrometer, Optical Rain Gauge, Automatic Weather Station, vertical profiling with GPS soundings, and a dual frequency GPS receiver, has been operating all these instruments to support the scientific research dealing with dynamics of the lower, middle and upper atmosphere, coupling between these regions and precipitating systems. Several interesting results have been obtained making use of the experimental facilities at NARL. It is, indeed, a difficult task to review all of them in a short paper. In this communication, an attempt has been made; however, to review the exciting scientific outcome resulted from Indian MST radar LAWP measurements, confining ourselves to dynamical and microphysical aspects of atmospheric processes in the troposphere and lower stratosphere. A variety of atmospheric phenomena occurring over a wide range of temporal and spatial scales are discussed, starting from microscale turbulence within the radar resolution volume to mesoscale processes, like convection and associated processes, and to synoptic and planetary scale waves with proper referencing, wherever required.

017224   Naidu P D (NO, National Institute of Oceanography, CSIR, Dona Paula, Goa-403 004, Email: divakar@nio.org) : Influence of monsoon upwelling on the planktonic foraminifera off Oman during Late Quaternary. Indian J Mar Sci 2007, 36(4), 322-31.

Planktonic foraminifer abundances, fluxes, test sizes, and coiling properties are influenced in various ways by the south-west monsoon winds and associated upwelling in the western Arabian Sea. The influence of monsoon driven upwelling on the planktonic foraminifer species abundances, coiling directions of Globigerinoides bulloides and Neogloboquadrina pachyderma and size variations of selected planktonic foraminifer species and carbon isotopic composition of Globigerina bulloides is summarized here.

017223   Moore A W (International GNSS Service Central Bureau, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr. MS 238-540, Pasadena, CA 91109, USA) : IGS network: Application of GPS to geodesy. Indian J Radio Space Phys 2007, 36(4), 261-7.

The Global Positioning System's satellites transmit time-dependent signals on two frequencies. When received on the ground and analyzed, these signals yield many benefits to geodesy, including terrestrial reference frames, plate and local motion, earth rotation parameters, and atmospheric information. The International GPS Service self-organized to efficiently coordinate a worldwide reference network of stations and analyze the data through international, voluntary collaboration. The products of this analysis are geodetically significant in themselves, and are used to great advantage by investigators in focused studies.

017222   Maitra A;Chakravarty K;Bhattacharya S;Bagchi S (Institute of Radio Physics and Electronics, , University of Calcutta, Email: animesh.maitra@gmail.com) : Propagation studies at Ku-band over an earth-space path at Kolkata. Indian J Radio Space Phys 2007, 36(5), 363-8.

Propagation measurements at Ku-band over an earth-space path have been carried out at Kolkata (22°34' N, 88°29' E) by receiving a signal at 11.172 GHz from the satellite NSS-6 (geostationary at 95°E). The amplitudes of the co-polar signal and the cross-polar component have been monitored along with the measurements of rain rate and drop size distribution by an optical raingauge and a Joss-type disdrometer, respectively. Three phenomena studied with the experimental data are rain attenuation, depolarization and scintillation. The rain attenuation observed experimentally tallies well with the values obtained from the point rain rate using a simple attenuation model, if the rain rate is low (less than 20 mm/h). The depolarization, indicated by an enhancement of the cross-polar component of the signal, is well correlated with the rain attenuation. The presence of large rain drops is found to have a more dominant role in determining the extent of depolarization than affecting the co-polar attenuation. The scintillation observations associated with the rain events indicate that the standard deviation of fast fluctuations increases with rain attenuation following a power-law.