Drivers of response to extreme weather warnings among marine fishermen

Extreme weather events, such as storms and cyclones, pose dire occupational hazards in marine fishing. Thus, warnings against such events can reduce risks to the life and property of fishing communities. This study is an attempt to assess the factors driving fishermen’s decision to respond to weather warnings. Mixed methods, such as exploratory fieldwork, literature review, and focus group discussions, helped in identifying the available weather warnings and hypothesizing the probable factors influencing response to the warnings in the marine fishing community in Maharashtra, India. The plausible drivers of response include perceived potential risk, credibility of the warning and its disseminators, community social capital, and other demographic characteristics. Data from a household survey, comprising 601 fishermen, is used to empirically test the hypotheses. The results suggest that trust in the source and disseminator of the warning is related to higher response rates. There is heterogeneity in the role of community social capital as a motivator to respond. Further, fishermen perceiving traditional information to be more reliable are less likely to respond frequently to the warnings. The findings of the study are relevant for designing interventions which can prompt high response rates to weather warnings from fishermen.     

An Experimental Evidence Of Non-Ducted Propagation During Daytime From The Esd Whistler Observations At Low Latitude Ground Station Jammu

The propagationmechanism of low latitude daytime whistlers is investigated on the basis of ground measurements made continuously during daytime in North India at Jammu (geomag. lat. 22°26°N;L = 1.17). On February 14, 1998 extremely small dispersion (ESD) whistlers with dispersion varying from 5–10 sec^1/2 in surprisingly large numbers were recorded at Jammu during daytime in the late afternoon. The results of a study of the characteristics of ESD whistlers are presented and the discussion indicates that ESD whistlers recorded are the VLF waves radiated from the return stroke of the lightning discharge launched at the ionosphere with different initial wave normal angles, propagated upwards under eitherquasi-longitudinal conditions or pro-longitudinal whistler mode, turned around at different heights due to quasi-transverse propagation and received at Jammu with the dispersion of the order of 5–10 sec^1/2. The validity of this suggestion has been tested by performing actualray-tracing computations in thepresence of equatorial anomaly model. This revised version was published online in July 2006 with corrections to the Cover Date.     

Laboratory Study of Air Sparging of TCE-Contaminated Saturated Soils and Ground Water

Air sparging has proven to be an effective remediation technique for treating saturated soils and ground water contaminated by volatile organic compounds (VOCs). Since little is known about the system variables and mass transfer mechanisms important to air sparging, several researchers have recently performed laboratory investigations to study such issues. This paper presents the results of column experiments performed to investigate the behavior of dense nonaqueous phase liquids (DNAPFs). specifically trichloroethylene (TCE), during air sparging. The specific objectives of the study were (1) to compare the removal of dissolved TCE with the removal of dissolved light nonaqueous phase liquids (LNAPLs). such as benzene or toluene; (2) to determine the effect of injected air-flow rate on dissolved TCE removal; (3) to determine the effect of initial dissolved TCE concentration on removal efficiency; and (4) to determine the differences in removal between dissolved and pure-phase TCE. The test results showed that (1) the removal of dissolved TCE was similar to that of dissolved LNAPL: (2) increased air-injection rates led to increased TCE removal at lower ranges of air injection, but further increases at higher ranges of air injection did not increase the rate of removal, indicating a threshold removal rate had been reached; (3) increased initial concentration of dissolved TCE resulted in similar rates of removal: and (4) the removal of pure-phase TCE was difficult using a low air-injection rate, but higher air-injection rates led to easier removal.     

Hydrochemical and Multivariate Statistical Evaluation of Heavy Metals in Shallow Alluvial Aquifers of North Brahmaputra Plain,India

The aim of this study was to display distribution and relationships of heavy elements in the unconfined, shallow alluvial aquifers of the lower Jia Bharali catchment and adjoining areas in central part of North Brahmaputra Plain (NBP), India using hydrochemical as well as multivariate statistical techniques such as principal component analysis (PCA) and cluster analysis. The original matrix was made up of 10 trace elements (As, Cd, Cu, Co, Cr, Fe, Mn, Pb, Ni and Zn) estimated from 50 shallow alluvial dug wells in both the wet and the dry season for a duration of 3 hydrological years (2008–2011). Except As, Cu and Zn all the other toxic metals in the shallow aquifers were found exceeding the WHO maximum permissible limits for drinking water. PCA extracted five varimax factors as geogenic, agricultural and anthropogenic explaining about 71.2% of the total variance in the wet season and 69.3% total variance in the dry season. Hierarchical cluster analysis classified the dug wells into two groups in the wet season and three groups in the dry season with respect to the heavy elements. The results emphasized the need for routine monitoring and management in order to avoid contamination of groundwater sources in the NBP with respect to the dissolved trace elements.     

Spatial variation and conditional simulation of seismic ground motion

Spatially varying ground motion (SVGM) may have influence on certain civil engineering structures with spatially extended superstructure and/or substructures. Conditional simulation of spatially varying ground motion (CSSVGM) may be viewed from two different perspectives. Most procedures available in the literature neglect the spatial variability in auto-spectral density (ASD) and estimate the SVGM through cross-spectral density (CSD) which was computed using the empirical coherency models. This paper proposes a coherency model that accounts for the spatial variability of ASD. A framework has been developed for the CSSVGM, through the mapping of both proposed coherency model and ASD over the footprint of an array. Current framework (existing in the literature) accounts for only the phase variability of SVGM while proposed framework accounts for both phase and amplitude variability. Ground motion generated from both perspectives is then assessed with the data recorded over SMART1 and LSST arrays. For the purpose of assessment, a definition of target spectrum based on the direction of arrival is explored. The effect of choice of coherency model on the simulated spatially varying ground motion is investigated first. Spectra resulting from both the perspectives are assessed against the target spectrum. An attempt has been made to predict the SVGM for a future event using a coherency model calibrated against a past event and an estimate of ASD of the seed ground motion. Finally, the effect of form of ASD (of a seed ground motion) on SVGM simulated is investigated by considering the ASD in different forms. Simulating SVGM through the mapping of both coherency model and ASD seems to be more appropriate than through CSD.     

Uncertainty of hydrologic simulation,and its impact on the design and the effectiveness of water conservation structures

Stochastic Environmental Research and Risk Assessment - The uncertainties associated with the simulation models are often ignored in operational hydrology. While many methods are available for...     

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.     

Intensified oxygen minimum zone on the western shelf of Bay of Bengal during summer monsoon: influence of river discharge

A study on biogeochemical cycling in the west coastal Bay of Bengal was undertaken during the peak discharge period to understand the influence of enhanced stratification and primary production on the possible intensification of the oxygen minimum zone (OMZ). Our study reveals that oxygen concentrations were below the detection limits in the northwestern (NW) coastal Bay of Bengal between 100 and 500 m associated with strong stratification and high phytoplankton biomass. Such low oxygen concentrations have never been reported so far from the coastal Bay of Bengal. Despite the existence of an environment conducive to denitrification in the coastal Bay of Bengal, accumulation of neither secondary nitrite nor nitrous oxide (N₂O) was observed. The absence of denitrification was reported to be caused by faster scavenging of organic matter and low bacterial respiration rates; in contrast, our results suggest that neither of these factors are potential reasons for the absence of denitrification in the coastal Bay of Bengal.     

Textural studies on red sediments of Bhimunipatnam,Andhra Pradesh,east coast of India

The study presents the textural characteristics of late Quaternary red sediments of Bhimunipatnam to understand the process of formation of these sediments. The red sediments are classified into (a) yellow sediments (b) reddish brown sediments (c) brick red sediments and (d) light yellow sediments sequence in the vertical litho section. The yellow sediments, rests on the khondalite basement, comprises of medium grained, moderate to poorly sorted and positively skewed. The rounded pebble beds with trough cross bedding indicate high energy turbulent conditions of deposition. The fining upward sequences indicate sediments were deposited under decreasing energy conditions under fluvial regime.The iron bearing minerals like garnets and pyriboles have undergone chemical weathering under high oxidizing environment resulting in addition of silt and clay to the reddish brown and brick red sediments and concretions were formed by carbonate precipitation. These processes caused changes in the mean grain size and sorting nature of these sediments which are originally aeolian in origin. The light yellow sediments were medium to fine grained, well sorted and similar to modern dune sands in terms of textural parameters. These sediments were deposited under low oxidation environmental conditions and acquired yellow colour due to Fe hydroxides.     

Vertical profile of aerosol single scattering albedo over west coast of India during W_ICARB

Altitude profile of aerosol Single Scattering Albedo (SSA), derived from simultaneous in-situ airborne measurements of the coefficients of aerosol absorption and scattering off the west coast of India over the Arabian Sea (AS), during January 2009 is presented. While both the absorption and scattering coefficients decreased with altitude, their vertical structure differed significantly. Consequently, the derived SSA, with a surface value of 0.94, decreased with altitude, illustrating increasing relative dominance of aerosol absorption at higher altitudes. Altitude profile of SSA, when examined in conjunction with that of hemispheric backscatter fraction, revealed that the continental influence on the aerosol properties was higher at higher altitude, rather than the effect of marine environment. During an east–west transect across the peninsular India at an altitude of ～2500 m (free troposphere), it was found that the aerosol scattering coefficients remained nearly the same over both east and west coasts.