Contrasting phytoplankton community structure and associated light absorption characteristics of the western Bay of Bengal

Absorption spectra, particulate pigments, and hydrochemical constituents were measured in the western Bay of Bengal (BoB) during July-August 2010 when influence of river discharge is at peak. Chromophoric dissolved organic matter (CDOM) absorption coefficient (a_CDOM(440)) displayed a significant inverse linear relationship with salinity in the surface waters implying conservative mixing of marine and terrestrial end members. The northern part of the study area is influenced by discharge from the river Ganga and a dominant terrestrial CDOM signal is seen. The southern part receives discharge from peninsular rivers with corresponding signals of higher CDOM than the linear model would indicate and higher UV-specific absorption coefficient (SUVA) indicating more aged and humified DOM. Lower contribution of CDOM to total non-water absorption and higher phytoplankton biomass (chlorophyll a absorption coefficient, a_ph(440)) but lower chlorophyll a specific phytoplankton absorption coefficient (a _ph ^* (440)) characterize the northern part, compared to the southern part. Chlorophyll b had a distinct linear relationship with chlorophyll a in the latter. The size index (SI) indicated dominance of microphytoplankton in the northern and nano and picophytoplankton in the southern parts. Chlorophyll a is significantly related to a _ph ^* (440) by an inverse power model in the northern part but by an inverse linear model in the southern part. Our study suggests that knowledge of the phytoplankton community structure is essential to improve chlorophyll a algorithm in the coastal Bay of Bengal.     

Simulated Annealing 2-D Nonlinear Inversion of Geomagnetic Deep Sounding Data Near Ujjain-Guna, India

--An attempt has been made to use the global optimization technique of Simulated Annealing (S.A.) inversion to interpret the conductivity structure derived from the geomagnetic deep sounding data of N-W India. The present results supersede the earlier result obtained by 2-D conventional linearized inversion. The earlier linearized inversion, following an iterative gradient search technique on the same data set, has been re-evaluated and further constrained through an exhaustive search of the parameter space. The conductive response of an hypothesized conductor located between Ujjain and Guna, India, has been modelled by this random search tool. The location of the proposed model is now in agreement with the theory, since the conductive bodies are centered exactly below the center of the response function. In an earlier attempt by linearized inversion, this was not feasible. The central body is located at a depth of 19 km from the surface, suggesting a thickness of 15 km and resistivity of 14 ohm.m. The resistivity contrast of this ensemble of conductive bodies with the background varies by a factor of 100 to 385. This low conductivity contrast with respect to the background is in conformity to the low temperature as inferred from the available heat-flow data in the region. A marginally different estimate of the conductivity (normally mid-crustal conductors are assigned conductivities of the order of 50 to 200 ohm.m) for the mid-crustal conductor has been found. Existence of a mid-crustal conductor is clearly indicated which was also not detected in the earlier study. Low geo-temperature gradients existing in the region rule out the possibility of a thermal origin for this mid-crustal conductor. A likely explanation could be due to the presence of graphitic carbon at lower crustal depths. However, the role of electrolytic fluid present in the interconnected pore--spaces of rocks may be another tangible explanation.     

Improvement of Monsoon Depressions Forecast with Assimilation of Indian DWR Data Using WRF-3DVAR Analysis System

An attempt is made to evaluate the impact of Doppler Weather Radar (DWR) radial velocity and reflectivity in Weather Research and Forecasting (WRF)-3D variational data assimilation (3DVAR) system for prediction of Bay of Bengal (BoB) monsoon depressions (MDs). Few numerical experiments are carried out to examine the individual impact of the DWR radial velocity and the reflectivity as well as collectively along with Global Telecommunication System (GTS) observations over the Indian monsoon region. The averaged 12 and 24 h forecast errors for wind, temperature and moisture at different pressure levels are analyzed. This evidently explains that the assimilation of radial velocity and reflectivity collectively enhanced the performance of the WRF-3DVAR system over the Indian region. After identifying the optimal combination of DWR data, this study has also investigated the impact of assimilation of Indian DWR radial velocity and reflectivity data on simulation of the four different summer MDs that occurred over BoB. For this study, three numerical experiments (control no assimilation, with GTS and GTS along with DWR) are carried out to evaluate the impact of DWR data on simulation of MDs. The results of the study indicate that the assimilation of DWR data has a positive impact on the prediction of the location, propagation and development of rain bands associated with the MDs. The simulated meteorological parameters and tracks of the MDs are reasonably improved after assimilation of DWR observations as compared to the other experiments. The root mean square errors (RMSE) of wind fields at different pressure levels, equitable skill score and frequency bias are significantly improved in the assimilation experiments mainly in DWR assimilation experiment for all MD cases. The mean Vector Displacement Errors (VDEs) are significantly decreased due to the assimilation of DWR observations as compared to the CNTL and 3DV_GTS experiments. The study clearly suggests that the performance of the model simulation for the intense convective system which influences the large scale monsoonal flow is significantly improved after assimilation of the Indian DWR data from even one coastal locale within the MDs track.     

Forecasting of groundwater level in hard rock region using artificial neural network

In hardrock terrain where seasonal streams are not perennial source of freshwater, increase in ground water exploitation has already resulted here in declining ground water levels and deteriorating its’ quality. The aquifer system has shown signs of depletion and quality contamination. Thus, to secure water for the future, water resource estimation and management has urgently become the need of the hour. In order to manage groundwater resources, it is vital to have a tool to predict the aquifer response for a given stress (abstraction and recharge). Artificial neural network (ANN) has surfaced as a proven and potential methodology to forecast the groundwater levels. In this paper, Feed-Forward Network based ANN model is used as a method to predict the groundwater levels. The models are trained with the inputs collected from field and then used as prediction tool for various scenarios of stress on aquifer. Such predictions help in developing better strategies for sustainable development of groundwater resources.     

Historical geomorphology and pedology of the Gandak Megafan,Middle Gangetic Plains,India

The Gandak megafan of eastern Uttar Pradesh and northwestern Bihar lies in the Middle Gangetic Plains. The Gandak River has shifted about 80 km to the east due to tilting in the last 5000 years. This has created a soil chronoassociation similar to the chronosequences found on some flights of river terraces. This chronoassociation has five members, QGD1-5. They are distinguished on the basis of profile development, clay mineralogy and calcium carbonate content. Chlorite transforms to vermiculite on a large scale from QGD1 to QGD3 and decreases drastically in member QGD4. Kaolinite and interstratified kaolinite-smectite are abundant in the older members of the chronoassociation. The youngest soils (QGD1:? < 500 b.p.) are found on the floodplains of the major rivers. QGD2 soils, like those of the Young Gandak Plain, date from? > 500 b.p., while QGD3 soils, like those on the Older Gandak Plain and Old Rapti Plains date back to 2500 b.p. QGD4 soils, like those on the Oldest Gandak Plain, are dated as? 5000 years b.p., whilst the oldest QGD5 soils, as on the Old Ghaghra Plain and Ganga-Ghaghra Interfluve, date back to 10000 b.p. These soils, which include pedogenic calcite and a? saline epipedon, indicate a dry climatic spell during the period 9000-11000 b.p. Faults developed on the megafan are not related to the basement structures.     

Temporal variation in the arsenic and metal accumulation in the maritime pine tree grown on contaminated soils

The uptake of arsenic and other metals (iron, manganese, copper, zinc, lead, nickel and tungsten) by Pinus pinaster Aiton (the maritime pine tree) growing in soils and tailings around an abandoned mine (northern Portugal) was investigated. Aerial parts of Pinus pinaster trees were sampled from three substrate areas: a background area, in mine contaminated soils and in tailings. Vegetation material was separated into needles and stems and subdivided into tissues of different maturities (1-, 2-, 3- and 4-years-old). The sampling of the substrate in each area was also undertaken. In general, vegetation concentrations were strongly related to substrate concentrations. The results show that the contents of several elements depend as much on the plant organ as on the age of the tissue. For the researched elements, this species shows a great variability in behavior depending on the age of the organ. The data indicate that the older needles constitute the best samples for use in a conjunct biogeochemical analysis of these elements.     

Implementation of RISAT-1 Hybrid Polarimetric Decomposition Techniques and Analysis Using Corner Reflector Data

With recent advances in polarimetry, Synthetic Aperture Radar (SAR) with Hybrid–polarity architecture, a demonstration of compact polarimetry enabled larger swath coverage, reduced PRF and SAR system complexity as compared to fully polarimetric systems. The first Hybrid Polarimetric Space-borne SAR in Earth Observation orbit, India’s Radar Imaging Satellite (RISAT-1) is a new-fangled gateway to remote sensing user community for land and oceanic applications. In response to a right-circular polarized transmitted signal, based on the derived stokes vectors, Stokes parameters are estimated to produce several useful quantitative measures for generating polarimetric decomposed image. m-delta, m-chi and m-alpha polarimetric decomposition methods along with suitable weighting functions in terms of three principal components are implemented which maps Stokes parameters to RGB image space for representing odd bounce, even bounce and volume scattering targets. Various RISAT-1 Hybrid Fine Resolution Stripmap Single-Look Complex SAR datasets acquired over deployed corner reflectors at calibration site, Shadnagar have been considered over which different hybrid polarimetric decomposition techniques are implemented using in-house developed software. Further analysis produced encouraging results with standard point targets like dihedral and trihedral corner reflectors against distributed targets in the same scene to demonstrate the scattering mechanisms as per their characteristics when interacted with a polarized signal were presented in this paper.     

Subsurface structure derived from detailed gravity and magnetic investigations along the Pala-Maneri traverse of the Main Central Thrust,NW Himalaya

A detailed, integrated gravity and magnetic study across the Main Central Thrust (MCT) along the Pala-Maneri traverse in Uttaranchal, NW Himalaya was carried out. The gravity data was acquired using a CG-3 gravity meter with an accuracy of 0.005 mGal, while magnetic data was acquired using a proton precession magnetometer with a station interval of 20 m. Data was collected along a 11.7 km, NE-SW traverse from Pala to Maneri along the proposed route of a hydroelectric headrace tunnel. The measured variation in the gravity field was approximately 70 mGal, with two prominent highs recorded at distances of 0.5 km, 7.5 km and lows at 3.0 km, 10.5 km from Maneri. The gravity highs can be attributed to presence of high-density rocks along the thrust planes. The sharp gravity low recorded at 10.5 km distance possibly indicates a sympathetic fault of the MCT that is highly saturated with fluids (water). The broad gravity low between 2.5 km and 4.0 km distance is likely to represent the gravity signature of the MCT itself. The measured variation in the magnetic field was approximately 285 nT. The associated gravity and magnetic signatures located several faults along the traverse including presence of the MCT at Kumaltigad.