Geminid Meteor shower activity 2003–2005 as observed by Gadanki radar

The distribution of meteor signals reflected from a backscatter radar is considered according to their duration. This duration time (T) is used to classify the meteor echoes and to calculate the mass index (S) of different meteoroids of shower plus sporadic background. Observational data on particle size distribution of the Geminid meteor shower are very scarce, particularly at low latitudes. In this paper the observational data from Gadanki radar (13.46°N, 79.18°E) have been used to determine the particle size distribution and the number density of meteoroids inside the stream of the Geminid meteor shower. The mean variation of meteor number density across the stream has been determined for three echo duration classes, T<0.4, T=0.4–1 and T>1 s. We are more interested in the appearance of echoes of various durations and therefore meteors of various masses in order to understand more on the filamentary structure of the stream. It is observed that the faint particle flux peaks earlier than the larger particles. We found a decreasing trend in the mass index values from the day of peak activity to the next observation days. The mass index profile was found to be U-shaped with a minimum value near the time of peak activity. The observed minimum s values are 1.64±0.05 and 1.65±0.04 in the years 2003 and 2005, respectively. The activity of the shower indicates the mass segregation of meteoroids inside the stream. Our results are best comparable with the “scissors” structure model of the meteoroid stream formation of Ryabova [2007. Mathematical modeling of the Geminid meteoroid stream. Mon. Not. R. Astron. Soc. 375, 1371–1380] by considering the asteroid 3200 Phaethon as an extinct comet.     

Catalytic nonthermal plasma reactor for the abatement of low concentrations of benzene

Oxidative decomposition of dilute benzene in air was carried out in a dielectric barrier discharge reactor with inner metal fiber electrode that was later modified with transition metal oxides. Typical results indicated the best performance of the designed reactor for the removal of dilute benzene, where conventional techniques may not be efficient. The introduction of transition metal oxides in the discharge zone increased the conversion of benzene and shifted the product distribution to total oxidation. The performance of the reactor was further improved on humidification of air stream. The better performance of MnO_x/SMF over CoO_x and SMF may be due to in situ decomposition of ozone that may lead to the formation of strong oxidant atomic oxygen, whereas the best performance with TiO₂/MnO_x/SMF may be assigned due to the synergy between ozone decomposition on MnO_x surface and photocatalytic action on TiO₂.     

The impact of paleo-channel on groundwater contamination,Andhra Pradesh,India

 Nakka vagu, a tributary of the River Manjira in the Medak district of Andhra Pradesh, has a catchment area of ∼500 km². Patancheru is an industrial development area (IDA) near the vagu. There are about 350 industries of varied nature (pulp, plastic, bulk drugs, pharmaceuticals, paints and steel rolling mills) that are engaged in the manufacture/processing of their respective products and that use water extensively. The hydrogeological setup has a bearing on the widespread contamination in the area because of discharge of industrial effluents into open land and streams. Several dug wells and boreholes situated in the study area have been monitored for water level fluctuations and quality variations. Pumping tests have been conducted to evaluate aquifer parameters. The geology, drainage, chemistry and other related anthropogenic factors play a major role in the spread of pollution in the area. Hence, it is very important to determine the degree of vulnerability to pollution based on hydrogeological factors. Amidst the granite terrain, the Nakka vagu has been identified as a paleo-channel (composed of clay–silt–sand facies); its presence in the area has immensely increased the spread of groundwater contamination. The transmissivity of the alluvial aquifer varies from 750 to 1315 m²/day. The adjoining granite has a transmissivity that varies from 30–430 m²/day. The thickness of the valley fill in the discharge region is about 10–12 m, with a lateral spread of 500–700 m, east of Nakka vagu. Received: 17 November 1999 · Accepted: 14 March 2000     

Seamounts an additional tool to confirm the nature of the crust and to locate possible mineral resources for dredging

Study of bathymetric data for the distal Bengal Fan reveals the presence of positive topographic features resembling seamounts. These features exhibit a relief of about 800 m above the surrounding seafloor at 4,400 m and are associated with large‐amplitude magnetic and gravity anomalies. Magnetic model studies suggest that one of the seamounts evolved along with the oceanic crust represented by the magnetic isochron A32 (～ 72 My), while the other seamount was emplaced over the Cretaceous Quiet Zone Crust with reversed polarity. The seamounts studied provide an environment for possible locations of polymetallic encrustations. Morphology of the seamounts depends on several factors, including physical and chemical composition of the magma, eruption style, sediment thickness, maturity of underlying crust, and time of origin. Studying the seamounts together with integrated geophysical and physical data gave useful indications of their evolution and the existence of possible mineral deposits.     

Air Pollution Modeling from Remotely Sensed Data Using Regression Techniques

There is a need for timely information about changes in the air pollution levels in cities for adopting precautionary measures. Keeping this in view, an attempt has been made to develop a model which will be useful to obtain air quality information directly from remotely sensed data easily and quickly. For this study pixel values, vegetation indices and urbanization index from IRS P6 LISS IV and Landsat ETM+ images were used to develop regression based models with Air Pollution Index (API), which were calculated from in-situ air pollutant information. It was found that among the 12 parameters of IRS, highest correlation exists between pixel values in NIR (Near Infra-Red) band (Pearson correlation ?0.77) and Normalized Difference Vegetation Index (NDVI) (Pearson correlation ?0.68) and both have inverse relationship with API. In case of Landsat, the highest correlation was observed in SWIR (Short Wave Infra-Red) band (Pearson correlation ?0.83) and NIR (Pearson correlation ?0.78). Both single and multivariate regression models were calibrated from best correlated variables from IRS and Landsat. Among all the models, multivariate regression model from Landsat with four most correlated variables gave the most accurate air pollution image. On comparison between the API modeled and API interpolated images, 90.5 % accuracy was obtained.     

Integrated approach for delineating potential zones to explore for groundwater in the Pageru River basin, Cuddapah District, Andhra Pradesh, India

Hydrogeomorphological, hydrogeological and geophysical investigations were carried out in the Pageru River basin of Cuddapah district, Andhra Pradesh, to delineate potential zones for future groundwater exploration. The study area is underlain by Proterozoic formations of the Indian Peninsula comprising limestones and shales as the sedimentary cover. Limestone and shale formations of the Cuddapah Super group that are later overlain by the Kurnool group (shale, limestone and quartzite) are exposed extensively. The high drainage density (2.61 km/km²) in the western region also suggests that the area is characterized by low permeable zones compared with low drainage density (1.04 km/km²) of the flood plains, which form the potential aquifers in the east. The hydro-geomorphological data are further supported from evidence of the water-table fluctuation in wells and resistivity of the saturated formations. The results indicate that the favourable, moderately favourable and poor zones characterized geomorphologically, have water-level fluctuations in the range of 0–2, 2–6 and above 6 m, respectively. The resistivities of these zones are also in the range of 1–26, 40–466, and >1,900 ohm-m. A few pumping tests have also been conducted to assess the broad range in the values of aquifer parameters. Based on these data, good to poor potential zones for obtaining groundwater have been delineated in the study area.

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Resumen Se llevaron a cabo investigaciones hidrogeomorfológicas, hidrogeológicas y geofísicas en la cuenca del Río Pageru del distrito Cuddapah, Andhra Pradesh, con objeto de delimitar zonas potenciales para exploración futura de aguas subterráneas. El área de estudio consiste de formaciones Proterozoicas de la Península India con calizas y lutitas como cubierta sedimentaria. Las formaciones de caliza y lutita del Grupo Cuddapah Superior afloran extensamente y están cubiertas por el Grupo Kurnool (lutita, caliza, y cuarcita). La alta densidad de drenaje (2.61 km/km²) en la región occidental también indica que el área se caracteriza por zonas de baja permeabilidad en comparación con las planicies de inundación de baja densidad (1.04 km/km²) que forman los acuíferos potenciales del oriente. Los datos hidrogeomorfológicos tienen apoyo adicional a partir de evidencia proveniente de la fluctuación del nivel freático en pozos y resistividad de las formaciones saturadas. Los resultados indican que las zonas caracterizadas geomorfológicamente como zonas favorables, moderadamente favorables, y pobres tienen fluctuaciones de niveles de agua en el rango de 0–2, 2–6, y mayor de 6 m, respectivamente. Las resistividades de estas zonas también se encuentran en el rango de 1–26, 40–466, y mayores de 1,900 ohm-m. Se realizaron algunas pruebas de bombeo para evaluar los amplios rangos que tienen los valores de los parámetros de los acuíferos. Basado en esta información se delimitaron zonas con potencial bueno a pobre para obtener agua subterránea en la zona de estudio.

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Résumé Des investigations hydrogéomorphologiques, hydrogéologiques et géophysiques ont été menées sur le bassin de la rivière Pageru du district de Cuddapah, Andhra Pradesh, pour délimiter les zones potentielles dans la future recherche deaux souterraines. La zone étudiée est, à la base, constituée par les formations protérozoïques de la péninsule indienne comprenant les calcaires et les shales de la couverture sédimentaire. Les calcaires et les shales du Super Groupe Cuddapah qui sont recouverts par le Groupe Kurnool (shale, calcire, quartzite) sont exposés de manière extensive. La densité importante de drainage (2.61 km/km²) dans la région ouest montre également que la zone est caractérisée par des perméabilités faibles par comparaison avec les plaines dinondation (densité de drainage: 1.04 km/km²), formant les aquifères potentiels de lEst. Les données hydrogéomorphologiques vont également dans le sens des données de fluctuation de la nappe et de résistivité des formations saturées. Les résultats indiquent que les zones caractérisées géomorphologiquement comme favorables, moyennement favorables et pauvres, possèdent des fluctuations respectives de lordre de 0 à 2, 2 à 6 et de plus de 6 m. La résistivité de ces zones est également de lordre de 1 à 26, 40 à 466 et de plus de 1900 ohm-m. Quelques pompages dessais ont également été conduits pour déterminer les valeurs moyennes des paramètres de laquifère. En se basant sur ces données, des zones potentielles bonnes à pauvres pour lexploitation des eaux souterraines ont été délimitées.

     

Air-sea Coupling During the Tropical Cyclones in the Indian Ocean: A Case Study Using Satellite Observations

In the years 1999 and 2001, three intense tropical cyclones formed over the northern Indian Ocean—two over the Bay of Bengal during 15–19 and 25–29 October, 1999 and one over the Arabian Sea during 21–28 May, 2001. We examined the thermal, salinity and circulation responses at the sea surface due to these severe cyclones in order to understand the air-sea coupling using data from satellite measurements and model simulations. It is found that the Sea Surface Temperature (SST) cooled by about 0.5 °–0.8 °C in the Bay of Bengal and 2 °C in the Arabian Sea. In the Bay of Bengal, this cooling took place beneath the cyclone center whereas in the Arabian Sea, the cooling occurred behind the cyclone only a few days later. This contrasting oceanic response resulted mainly from the salinity stratification in the Bay of Bengal and thermal stratification in the Arabian Sea and the associated mixing processes. In particular, the cyclones moved over the region of low salinity and smaller mixed layer depth with a distinct mixed layer deepening to the left side of the cyclone track. It is envisaged that daily satellite estimates of SST and Sea Surface Salinity (SSS) using Outgoing Longwave Radiation (OLR) and model simulated mixed layer depth would be useful for the study of tropical cyclones and prediction of their path over the northern Indian Ocean.