Fluxes of amino acids and hexosamines to the deep Arabian Sea

Results of organic carbon, total nitrogen, amino acid and hexosamine analyses of samples collected during time-series sediment trap investigations in the Arabian Sea are presented. Samples were taken over a period of years at two depths at each of three locations in the western, central and eastern part of the basin. Seasonal changes in amino acid contents and their spectral distributions show that degradation of organic matter in the water column is reduced during the monsoons, which are the high-flux periods in the western and central Arabian Sea. At the eastern site more degraded material of possibly recycled marine or terrestrial origin reaches the traps during the late summer peak fluxes. The results of hexosamine analyses suggest that bacterial biomass is relatively enriched on particles sinking in the water column and, to a larger extent, at the sediment-water interface. Decomposition between intermediate and deep water results in a loss of 30–40% of total organic carbon and more than 40% of amino acids. Comparison of the measured accumulation rates of organic carbon in sediment traps with those of organic carbon preserved in sediments show that more than 85% is lost before final burial in the sediments. Organic matter preservation in the Arabian Sea is higher than the average for the open ocean; this maybe due to the abundance of refractory organic matter of recycled marine or terrestrial origin.     

Dissolved Folin Phenol Active Substances (Tannin and Lignin) in the Seawater along the West Coast of India

Information on the distribution of dissolved Folin phenol active substances (FPAS) such as tannin and lignin in the seawater along the west coast of India is provided. Notable amounts of FPAS (surface concentrations: 80 g/l to 147 g/l and bottom concentrations: 80 g/l to 116 g/l) were detected in the seawater along the coast. The distribution pattern brings about a general depth-wise decrease. A seaward decrease was observed in the southern stations whereas reverse was the case in northern stations. A significant negative correlation was observed between FPAS concentration and dissolved oxygen in sub-surface samples. The appreciable amounts of FPAS detected in the coastal waters indicate the presence of organic matter principally originating from terrestrial (upland and coastal marsh) ecosystems in the marine environment. In this context, they may be used as tracers to determine the fate of coastalborn dissolved organic matter in the ocean and to determine directly the relationship between allochthonous and autochthonous organic matter.     

Automated star–galaxy segregation using spectral and integrated band data for TAUVEX/ASTROSAT satellite data pipeline

We employ an Artificial Neural Network (ANN) based technique to develop a pipeline for automated segregation of stars from the galaxies to be observed by Tel-Aviv University Ultra-Violet Experiment (TAUVEX). We use synthetic spectra of stars from UVBLUE library and selected International Ultraviolet Explorer (IUE) low-resolution spectra for galaxies in the ultraviolet (UV) region from 1250 to 3220 Å as the training set and IUE low-resolution spectra for both the stars and the galaxies as the test set. All the data sets have been pre-processed to get band integrated fluxes so as to mimic the observations of the TAUVEX UV imager. We also perform the ANN based segregation scheme using the full length spectral features (which will also be useful for the ASTROSAT mission). Our results suggest that, in the case of the non-availability of full spectral features, the limited band integrated features can be used to segregate the two classes of objects; although the band data classification is less accurate than the full spectral data classification.     

Impact of Land Surface Heterogeneity on Mesoscale Atmospheric Dispersion

Prior numerical modelling studies show that atmospheric dispersion is sensitive to surface heterogeneities, but past studies do not consider the impact of a realistic distribution of surface heterogeneities on mesoscale atmospheric dispersion. While these focussed on dispersion in the convective boundary layer, the present work also considers dispersion in the nocturnal boundary layer and above. Using a Lagrangian particle dispersion model (LPDM) coupled to the Eulerian Regional Atmospheric Modeling System (RAMS), the impact of topographic, vegetation, and soil moisture heterogeneities on daytime and nighttime atmospheric dispersion is examined. In addition, the sensitivity to the use of Moderate Resolution Imaging Spectroradiometer (MODIS)-derived spatial distributions of vegetation characteristics on atmospheric dispersion is also studied. The impact of vegetation and terrain heterogeneities on atmospheric dispersion is strongly modulated by soil moisture, with the nature of dispersion switching from non-Gaussian to near-Gaussian behaviour for wetter soils (fraction of saturation soil moisture content exceeding 40%). For drier soil moisture conditions, vegetation heterogeneity produces differential heating and the formation of mesoscale circulation patterns that are primarily responsible for non-Gaussian dispersion patterns. Nighttime dispersion is very sensitive to topographic, vegetation, soil moisture, and soil type heterogeneity and is distinctly non-Gaussian for heterogeneous land-surface conditions. Sensitivity studies show that soil type and vegetation heterogeneities have the most dramatic impact on atmospheric dispersion. To provide more skilful dispersion calculations, we recommend the utilisation of satellite-derived vegetation characteristics coupled with data assimilation techniques that constrain soil-vegetation-atmosphere transfer (SVAT) models to generate realistic spatial distributions of surface energy fluxes.     

A baseline study of trace metals in a coral reef sedimentary environment,Lakshadweep Archipelago

Surficial and core samples collected from the sedimentary microenvironments of Lakshadweep Archipelago were analysed for their trace metal contents. The synoptical relations in spatial distributions with respect to environmental conditions such as pH, organic carbon and sediment texture were inter-correlated. Some of the metals exhibited good correlations with Fe/Mn, which reflect their similarity in distribution rather than anthropogenic enrichment. Inter-relating the variations in metal—pH relationships with metal—organic carbon, in general, those which exhibited positive correlations with pH, displayed negative interactions with organic carbon content and vice versa. Comparatively, higher values of Fe in the mangrove area of one of the islands highlight the possibility of precipitation of Fe as iron sulphides, which are common in mangrove ecosystem. Based on the contamination factors for Pb, Zn and Cd, as well as the geo-accumulation index of Cd, it can be generalised that some of the islands remain polluted with respect to these elements. An evaluation based on pollution load index shows that none of the islands surveyed for this study posed a serious threat in trace metal pollution. Bray Curtis similarity index was computed to find out the similarity among metals/islands, using non-transformed data of metal concentrations. Group linkage clustering technique was used for drawing dendrograms to show the similarity among them.     

Some aspects of an early summer monsoon onset over Andaman Sea and further progress towards the Indian mainland

This work addresses the mechanisms that leads to an early onset of monsoon over Andaman Sea but advances further rapidly (slowly) to the Indian mainland resulting in the early (delayed) onset over Kerala. The upper tropospheric temperature, production of kinetic energy (KE) and outgoing long wave radiation (OLR) from the month of May till onset over Kerala are analysed for two delayed onset years (1997, 1995) and two early onset years (2004, 1990). It is observed that the maximum temperature over Tibetan plateau (TP), an increase in the production of KE and strong equatorial convection in early May, is associated with early onset over Andaman Sea. However, when there is a lull in advance of monsoon after the early onset over Andaman Sea, shifting of the warm region south of TP, weak production of KE in the lower troposphere and convective region shifting to Western Pacific resulted in the delayed onset over Kerala in 1997 and 1995. During the early onset years viz. 2004 and 1990, the warm region moving westwards, high production of KE extending to mid troposphere and deep convection moving westwards in the north Indian Ocean (10–15°N) is noticed.     

Remote sensing application in the study of migration and offset of coastal inlets

The coastal zone of Kerala with moderate energy, monsoonal-storm-dominated wave climate, together with a microtidal range, falls under the major tectonic class of the Amerotrailing edge coasts. In order to have an effective management of this coastal zone, one requires detailed information on various types of coastal landforms and the related processes acting on them. Coastal inlets are one among such landforms, which are relatively short and narrow tidal channels connecting bays and lagoons to the ocean. Coastal inlets and the related landforms form an important type of coastal feature. An examination of coastal maps from any area in the world will reveal that coastal inlets are of migratory and offset in nature. In the present study the migration pattern and offset behaviour of some of the inlets of Kerala coast have been examined using IRS-IA LISS II data and Survey of India topographic sheets. The study reveals that geocoded IRS-IA LISS II data could provide accurate geometrical information which may considerably minimise the field check.     

Perturbation of eigenfrequencies of a cylinder due to a ridge on the surface

Summary An infinite cylinder is assumed to have a small ridge on the surface. The effect of the ridge on the eigenfrequencies of flute mode of oscillation is obtained in the linear approximation. The usefulness of these results in seismological problems is indicated.     

Granite-molybdenite association in Kerala in relation to taphrogenic metallogeny

Two molybdenite-bearing granites from the Kerala region, namely, the Chengannoor and the Ambalavayal granites are discussed here in terms of their salient geochemical characters. The geochemistry of the host rocks indicates a peraluminous, calc-alkaline to alkali-calcic nature and the element levels show good fit with the proposed ‘finger-prints’ for granite-molybdenite systems. Fluid inclusion studies suggest that Mo was probably partitioned in vapour phase, which subsequently combined with available sulphur. Regional distribution of molybdenite strongly favours the view of a molybdenum province in the southern part of the Indian shield. Associations of rare metal mineralization with the riftcontrolled acid magmatic phase in the Kerala region are suggestive of a late Precambrian —Early Palaeozoic taphrogenic metallogeny.