Ionic characters of lake water of Bharti promontory,Larsemann Hills,East Antarctica

The Larsemann Hills area represents a unique environmental setting between marine and glacial ecosystems. One of the promontories of this region, named Bharti, depicting similar set up was selected for the study of chemical parameters with special reference to its ionic characters. Water samples from 6 selected lakes of Bharti promontory, Larsemann Hills area were collected during the austral summer of 2004–05 and analysed for major ionic concentration and Total Dissolved Solid (TDS). This study is aimed at understanding the water chemistry of lakes of this island with emphasis on correlation between different ionic concentrations, TDS and its possible causes. The study will provide baseline data that will be useful for planning further studies. Analytical result shows that the water chemistry of these lakes is mainly governed by the lithology, precipitation, drainage and marine environment. Minor contribution of evaporation, has also been observed on the chemistry of one of the lake water. The main source of water for these lakes comes mainly from snow precipitation and its melting. The drainage line mostly goes towards eastern direction for these lakes.     

A drought climatology for Mauritius using the standardized precipitation index

This study presents a high-resolution and multi-temporal drought climatology for Mauritius based on calculated standardized precipitation index (SPI) using mean monthly rainfall for the period 1953–2007. A monthly mean SPI varying from +3.4 to ?2.7 indicates the occurrence of extremely wet and dry conditions, and collocated SPI indicates more frequent mild drought conditions. Spatial maps of rainfall trends and SPI show mostly neutral to severely dry conditions, but sparse regions of extremely wet and dry conditions are also observed. An increase in the frequency of dry years after the 1990s is noted, while most of the extreme wet conditions are found to have occurred between 1972 and 1988. More frequent short-duration wet events are observed on the 3- and 6-month time scales compared to dry events. On the 12- and 24-month time scales the frequency of both dry and wet periods is almost the same, with the dry events lasting longer.     

Installation of solar chromospheric telescope at the Indian Astronomical Observatory,Merak

We report the observations of the solar chromosphere from a newly commissioned solar telescope at the incursion site near Pangong Tso lake in Merak (Leh/Ladakh). This new \(\hbox {H}_{\alpha }\) telescope at the Merak site is identical to the Kodaikanal \(\hbox {H}_{\alpha }\) telescope. The telescope was installed in the month of August 2017 at the Merak site. The telescope consists of a 20-cm doublet lens with additional re-imaging optics. A Lyot filter with 0.5 Å passband isolates the Balmer line of the hydrogen spectra to make the observations of the solar chromosphere. The observations made in \(\hbox {H}_{\alpha }\) wavelength delineates the magnetic field directions at the sunspot and the quiet regions. A CCD detector records the images of the chromosphere with a pixel resolution of 0.27\(^{\prime \prime }\) and covers 9.2\(^{\prime }\) field-of-view. This telescope has a good guiding system that keeps the FoV in the intended position. We report the development of control software for tuning the filter unit, control detector system, observations and calibration of the data to make it useful for the scientific community. Some preliminary results obtained from the Merak \(\hbox {H}_{\alpha }\) telescope are also presented. This high altitude facility is a timely addition to regularly obtain \(\hbox {H}_{\alpha }\) images around the globe.     

Ultra-tight GPS/INS/PL integration: a system concept and performance analysis

The architecture of the ultra-tight GPS/INS/PL integration is the key to its successful performance; the main feature of this architecture is the Doppler feedback to the GPS receiver tracking loops. This Doppler derived from INS, when integrated with the carrier tracking loops, removes the Doppler due to vehicle dynamics from the GPS/PL signal thereby achieving a significant reduction in the carrier tracking loop bandwidth. The bandwidth reduction provides several advantages such as: improvement in anti-jamming performance, and increase in post correlated signal strength which in turn increases the dynamic range and accuracy of measurements. Therefore, any degradation in the derived Doppler estimates will directly affect the tracking loop bandwidth and hence its performance. The quadrature signals from the receiver correlator, I (in-phase) and Q (quadrature), form the measurements, whereas the inertial sensor errors, position, velocity and attitude errors form the states of the complementary Kalman filter. To specify a reliable measurement model of the filter for this type of integrated system, a good understanding of GPS/PL signal characteristics is essential. It is shown in this paper that phase and frequency errors are the variables that relate the measurements and the states in the Kalman filter. The main focus of this paper is to establish the fundamental mathematical relationships that form the measurement model, and to show explicitly how the system error states are related to the GPS/PL signals. The derived mathematical relationships encapsulated in a Kalman filter, are tested by simulation and shown to be valid.

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Identification of landslide susceptible villages around Kalsubai region,Western Ghats of Maharashtra using geospatial techniques

Heavy rainfall triggered landslides are on the rise along the Western Ghats making it a matter of priority to identify landslide-prone areas well in advance. The present effort is aimed at identifying landslide susceptible villages (LSV) around the Kalsubai region of Deccan volcanic province (DVP), Maharashtra, India from 8 weighted landslide parameters- rainfall, slope, lithology, land use and land cover (LULC), soil properties, relative relief, aspect and lineament. These parameters were combined with advanced remote sensing (RS) data and processed in geographical information system (GIS) as well as in image processing software, which are an integral part of geospatial techniques. Out of the total 59 villages, the study identified 9 villages are situated in very high, 13 in high, 12 in moderate, 11 in low and 14 in very low risk zones. Our data reveals incessant heavy rains and steep slopes are the dominant factors in triggering landslides, exacerbated by anthropogenic activity prevalent in the study area. The spatial and non-spatial database created will help to take effective steps in preventing and/or mitigating landslide disasters in the study area. The methodology can be applied to identify other landslide prone areas in a cost effective way.     

Petrogenesis of massif-type anorthosite complex, Gruber, Central Dronning Maud Land, East Antarctica： Implications for magma source and evolution

The origin of anorthosite and associated igneous gabbronorite and ferrodiorite was investigated through detailed study of a typical massif-type anorthosite complex from Gruber, Central Dronning Maud Land, East Antarctica. Field observations showed that the Gruber Complex is made up of gabbronorite-anorthosite pluton which was intruded by ferrodiorite dykes. Systematic samples collected from the Gruber Complex revealed significant geochemical variations within the region. Four rock types have been identified, based on modal proportions of mineral phases and their geochemistry data. Clinopyroxene-gabbronorite and plagioclase-gabbronorite are the two types of gabbronorite with the dominance of clinopyroxene and plagioclase, respectively. Anorthosite is represented by rocks having predominance of plagioclase with minor clinopyroxene. Ferrodiorite is characterized by modal abundance of orthopyroxene and Fe-Ti oxide. Major and trace element systematics showed that all the four rock types are co-magmatic and are related through fractional crystallization. Based on this study, it is reported that clinopyroxene was the first phase to crystallize followed by plagioclase and then Fe-Ti oxides. Furthermore, trace element composition of the parental melt was calculated using LA-ICPMS analysis of the most primitive, pure clinopyroxene found in the clinopyroxene gabbronorite. Our analyses suggested that the parental melt was similar to that of continental arc basalt and showed signatures of subduction-related metasomatism. Based on mineral chemical and geochemical data, it is interpreted that the parent melt went through changing sequence of crystallization which led to the formation of massive anorthosite.     

Response of Sandy Lake in Schirmacher Oasis,East Antarctica to the glacial-interglacial climate shift

Freshwater lakes in Antarctica fluctuate from ice-free state (during austral summer) to ice-cover state (during austral winter). Hence the lakes respond instantly to the seasonal climate of the region. The Antarctic seasons respond sharply to the glacial and interglacial climates and these signatures are archived in the lake sediments. A sediment core from Sandy Lake, a periglacial lake located in Schirmacher Oasis of East Antarctica records distinct changes in grain-size, C, N, C/N ratios (atomic), δ¹³C_OM and δ¹⁵N_OM contents during the last 36 ky. The contents of the sedimentary organic matter (OM) proxies (C_org ~ 0.3 ± 0.2%, C/N ratios ~9 ± 5 and δ¹³C_OM ~?18 ± 6‰) indicate that the OM in this lake sediment is a product of mixing of terrestrial and lacustrine biomass. Distinctly lower contents of C_org (~0.2%) and sand (~50%), low C/N ratios (~8) and depleted δ¹³C_OM (~?20‰) during the Last Glacial Maximum (LGM: 32–17 ky BP based on Vostok Temperatures) suggest greater internal (autochthonous) provenance of organic matter and limited terrestrial (allochthonous) inputs probably due to long and intense winters in the Antarctic. Such intense winters might have resulted the lake surface to be ice-covered for most part of the year when the temperatures remained consistently colder than the Holocene temperatures. The denitrification within the lake evident by enriched δ¹⁵N_OM (>10‰) during Antarctic LGM might have resulted from oxygen-limitation within the lake environment caused by insulated lake surface. The gradual increases in δ¹³C_OM, C/N and sand content starting at ~11 ky BP and attaining high values (~?11‰, ~10 and ~80% respectively) at ~6 ky BP together suggest a subtle change in the balance of sources of organic matter between algal and macrophyte/bryophyte nearly 8–9 ky later to the beginning of the deglaciation. Thus the seasonal opening-up of the Sandy Lake similar to the modern pattern started with the establishment of the optimum temperature conditions (i.e., 0 °C anomaly) in the Antarctic, prior to which the lake environment might have remained mostly insulated or closed.     

Chemical characterization and multivariate analysis of atmospheric PM<Subscript>2.5</Subscript> particles

The new European Council Directive (PE-CONS 3696/07) frames the inhalable (PM₁₀) and fine particles (PM_2.5) on priority to chemically characterize these fractions in order to understand their possible relation with health effects. Considering this, PM_2.5 was collected during four different seasons to evaluate the relative abundance of bulk elements (Cl, S, Si, Al, Br, Cu, Fe, Ti, Ca, K, Pb, Zn, Ni, Mn, Cr and V) and water soluble ions (F⁻, Cl⁻, NO₂ ⁻, NO₃ ⁻, SO₄ ²⁻, Na⁺, NH₄ ⁺, Ca²⁺ and Mg²⁺) over Menen, a Belgian city near the French border. The air quality over Menen is influenced by industrialized regions on both sides of the border. The most abundant ionic species were NO₃ ⁻, SO₄ ²⁻ and NH₄ ⁺, and they showed distinct seasonal variation. The elevated levels of NO₃ ⁻ during spring and summer were found to be related to the larger availability of the NO_x precursor. The various elemental species analyzed were distinguished into crustal and anthropogenic source categories. The dominating elements were S and Cl in the PM_2.5 particles. The anthropogenic fraction (e.g. Zn, Pb, and Cu) shows a more scattered abundance. Furthermore, the ions and elemental data were also processed using principal component analysis and cluster analysis to identify their sources and chemistry. These approach identifies anthropogenic (traffic and industrial) emissions as a major source for fine particles. The variations in the natural/anthropogenic fractions of PM_2.5 were also found to be a function of meteorological conditions as well as of long-range transport of air masses from the industrialized regions of the continent. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.