Multi-decadal variation of the net downward shortwave radiation over south Asia: The solar dimming effect

The solar radiation flux at the earth's surface has gone through decadal changes of decreasing and increasing trends over the globe. These phenomena known as dimming and brightening, respectively, have attracted the scientific interest in relation to the changes in radiative balance and climate. Despite the interest in the solar dimming/brightening phenomenon in various parts of the world, south Asia has not attracted great scientific attention so far. The present work uses the net downward shortwave radiation (NDSWR) values derived from satellites (Modern Era Retrospective-analysis for Research and Applications, MERRA 2D) in order to examine the multi-decadal variations in the incoming solar radiation over south Asia for the period of 1979-2004. From the analysis it is seen that solar dimming continues over south Asia with a trend of -0.54 Wm(-2) yr(-1). Assuming clear skies an average decrease of -0.05 Wm(-2)yr(-1) in NDSWR was observed, which is attributed to increased aerosol emissions over the region. There is evidence that the increase in cloud optical depth plays the major role for the solar dimming over the area. The cloud optical depth (MERRA retrievals) has increased by 10.7% during the study period, with the largest increase to be detected for the high-level (atmospheric pressure P < 400 hPa) clouds (31.2%). Nevertheless, the decrease in solar radiation and the role of aerosols and clouds exhibit large monthly and seasonal variations directly affected by the local monsoon system, the anthropogenic and natural aerosol emissions. All these aspects are examined in detail aiming at shedding light into the solar dimming phenomenon over a densely populated area. (C) 2011 Elsevier Ltd. All rights reserved.

Recent microtremors near the Idukki Reservoir, Kerala, South India

The continuing low-level seismicity in the vicinity of the Idukki Reservoir, Kerala, is interesting from the perspective of hydrologically triggered earthquakes. While the frequency of triggered earthquakes in the vicinity of a reservoir usually reduces with time and the largest earthquake usually occurs within a few years on the initial filling, the triggered seismicity in the proximity of the Idukki Reservoir seems to be showing a second, delayed peak, as the 1977 (M 3.5) tremor was followed by a slightly larger event in 2011, 24 years after the first burst of activity. Quite unprecedented in the context of reservoir-triggered sequences, we consider this delayed sequence as the hydrologic response of a critically stressed hypocentral region, to monsoonal recharging. The sustained activity several decades after the impoundment and the temporal relation with the monsoon suggest that at least some parts of the reservoir region continue to retain the potential for low-level seismic activity in response to hydrologic cycles.

Causality analysis of groundwater dynamics based on a Vector Autoregressive model in the semi-arid basin of Gundal (South India)

Causal relationships existing between observed levels of groundwater in a semi-arid sub-basin of the Kabini River basin (Karnataka state, India) are investigated in this study. A Vector Auto Regressive model is used for this purpose. Its structure is built on an upstream/downstream interaction network based on observed hydro-physical properties. Exogenous climatic forcing is used as an input based on cumulated rainfall departure. Optimal models are obtained thanks to a trial approach and are used as a proxy of the dynamics to derive causal networks. It appears to be an interesting tool for analysing the causal relationships existing inside the basin. The causal network reveals 3 main regions: the Northeastern part of the Gundal basin is closely coupled to the outlet dynamics. The Northwestern part is mainly controlled by the climatic forcing and only marginally linked to the outlet dynamic. Finally, the upper part of the basin plays as a forcing rather than a coupling with the lower part of the basin allowing for a separate analysis of this local behaviour. The analysis also reveals differential time scales at work inside the basin when comparing upstream oriented with downstream oriented causalities. In the upper part of the basin, time delays are close to 2 months in the upward direction and lower than 1 month in the downward direction. These time scales are likely to be good indicators of the hydraulic response time of the basin which is a parameter usually difficult to estimate practically. This suggests that, at the sub-basin scale, intra-annual time scales would be more relevant scales for analysing or modelling tropical basin dynamics in hard rock (granitic and gneissic) aquifers ubiquitous in south India. (c) 2012 Elsevier B.V. All rights reserved.

Ultrahigh-temperature metamorphism from an unusual corundum plus orthopyroxene intergrowth bearing Al-Mg granulite from the Southern Marginal Zone, Limpopo Complex, South Africa

The Southern Marginal Zone of the Limpopo Complex is composed of granite-greenstone cratonic rocks reworked by a Neoarchean high-grade tectono-metamorphic event. Petrographic and mineral chemical characterization of an Al-Mg granulite from this zone is presented here. The granulite has a gneissic fabric with distinct Al-rich and Si-rich layers, with the former preserving the unusual lamellar (random and regular subparallel) intergrowths of corundum and symplectic intergrowth of spinel with orthopyroxene. The Al-rich layer preserves mineral assemblages such as rutile with orthopyroxene + sillimanite +/- A quartz, Al-rich orthopyroxene (similar to 11 wt%), spinel + quartz, and corundum in possible equilibrium with quartz, while the Si-rich layer preserves antiperthites and orthopyroxene + sillimanite +/- A quartz, all considered diagnostic of ultrahigh-temperature metamorphism. Application of Al-in-opx thermometry, ternary feldspar thermometry and construction of suitable pressure-temperature phase diagrams, compositional and model proportion isopleth results indicate P-T conditions as high as similar to 1,050-1,100 A degrees C, and similar to 10-12 kbars for the Al-Mg granulite. Our report of ultrahigh-temperature conditions is significant considering that the very high temperature was reached during decompression of an otherwise high-pressure granulite complex (clockwise P-T path), whereas most other ultrahigh-temperature granulites are linked to magma underplating at the base of the crust (counterclockwise P-T path).

Coalescent Method in Conjunction with Niche Modeling Reveals Cryptic Diversity among Centipedes in the Western Ghats of South India

Background: There has been growing interest in integrative taxonomy that uses data from multiple disciplines for species delimitation. Typically, in such studies, monophyly is taken as a proxy for taxonomic distinctiveness and these units are treated as potential species. However, monophyly could arise due to stochastic processes. Thus here, we have employed a recently developed tool based on coalescent approach to ascertain the taxonomic distinctiveness of various monophyletic units. Subsequently, the species status of these taxonomic units was further tested using corroborative evidence from morphology and ecology. This inter-disciplinary approach was implemented on endemic centipedes of the genus Digitipes (Attems 1930) from the Western Ghats (WG) biodiversity hotspot of India. The species of the genus Digitipes are morphologically conserved, despite their ancient late Cretaceous origin. Principal Findings: Our coalescent analysis based on mitochondrial dataset indicated the presence of nine putative species. The integrative approach, which includes nuclear, morphology, and climate datasets supported distinctiveness of eight putative species, of which three represent described species and five were new species. Among the five new species, three were morphologically cryptic species, emphasizing the effectiveness of this approach in discovering cryptic diversity in less explored areas of the tropics like the WG. In addition, species pairs showed variable divergence along the molecular, morphological and climate axes. Conclusions: A multidisciplinary approach illustrated here is successful in discovering cryptic diversity with an indication that the current estimates of invertebrate species richness for the WG might have been underestimated. Additionally, the importance of measuring multiple secondary properties of species while defining species boundaries was highlighted given variable divergence of each species pair across the disciplines.

Under-representation of intrinsic terminators across bacterial genomic islands: Rho as a principal regulator of xenogenic DNA expression

Two transcription termination mechanisms - intrinsic and Rho-dependent - have evolved in bacteria. The Rho factor occurs in most bacterial lineages, and has been hypothesized to play a global regulatory role. Genome-wide studies using microarray, 2D-gel electrophoresis and ChIP-chip provided evidence that Rho serves to silence transcription from horizontally acquired genes and prophages in Escherichia coli K-12, implicating the factor to be a part of the ``cellular immune mechanism'' protecting against deleterious phages and aberrant gene expression from acquired xenogenic DNA. We have investigated this model by adopting an alternate in silico approach and have extended the study to other species. Our analysis shows that several genomic islands across diverse phyla have under-representation of intrinsic terminators, similar to that experimentally observed in E. coli K-12. This implies that Rho-dependent termination is the predominant process operational in these islands and that silencing of foreign DNA is a conserved function of Rho. From the present analysis, it is evident that horizontally acquired islands have lost intrinsic terminators to facilitate Rho-dependent termination. These results underscore the importance of Rho as a conserved, genome-wide sentinel that regulates potentially toxic xenogenic DNA. (C) 2012 Elsevier B.V. All rights reserved.

Shola habitats on sky islands: status of research on montane forests and grasslands in southern India

The Shola habitat on the high elevation sky islands of the Western Ghats in southern India is a unique habitat. Although this habitat hosts a disproportionately high level of endemism and is threatened by anthropogenic modifications, it has received little research attention. We compiled publications of research conducted in this habitat from scientific databases and the grey literature to examine trends in publication. For a quantitative summary, all publications were classified according to the taxa of research and the broad topic of research. We identified 279 publications from 1964 and found an almost threefold increase in the number of publications and diversity of research topics studied over the last decade. Studies on flora, birds and mammals have been numerous (62% of the studies examined), but certain taxa like fish (1%) have been ignored. Most studies (65%) are descriptive, focusing on diversity, distribution trends and management suggestions, while surprisingly few have concentrated on climate change, ecological restoration and invasive species, all major threats to this landscape. We have identified some key gaps in research and conservation focus that future studies could address. We also suggest that initiatives like edited volumes and special journal sections, along with the use of creative commons licensed data-sharing portals, can be used to usher unpublished work into the public domain.

ORTHOPYROXENE plus SILLIMANITE PREDATING SAPPHIRINE plus QUARTZ: A RARE CASE OF ULTRAHIGH-TEMPERATURE METAMORPHISM FROM THE CENTRAL ZONE, LIMPOPO COMPLEX, SOUTH AFRICA

Sapphirine + quartz and orthopyroxene + sillimanite occur in garnet from an Mg-Al granulite from the Central Zone of the Limpopo Complex in South Africa. Textural evidence and a chemical gradient in garnet between the zones preserving the inclusions argue for the formation of sapphirine + quartz after orthopyroxene + sillimanite. Petrological observations, pressure-temperature phase diagrams, and compositional and model proportion results on isopleths indicate the sapphirine + quartz + garnet + orthopyroxene (high-Al) assemblage as the peak metamorphic assemblage (similar to 1050 degrees C at similar to 8.5 kbars), whereas orthopyroxene (low-Al) + sillimanite represents the prograde stage (at ca. 900 degrees C at similar to 8.5 kbars). Our report of these two diagnostic ultrahigh-temperature mineral assemblages in garnet from an Mg-Al granulite is unique, given the rare occurrence of sapphirine + quartz postdating orthopyroxene + sillimanite assemblage in granulites.

Microearthquake activity near the Idukki Reservoir, south India: A rare example of renewed triggered seismicity

Earthquakes triggered by artificial reservoirs have been documented for more than seven decades and the processes leading to this phenomenon are fairly well understood. Larger among such earthquakes are known to occur within a few years of reservoir impoundment and usually the activity decreases with time. A documented example of Reservoir Triggered Seismicity (RTS), the Idukki Reservoir in Kerala, south India, impounded in 1975, is an exception wherein the triggered activity has been revived in 2011, nearly 35 years after the initial burst of activity in 1977, two years after the dam was filled. The magnitude of the largest shock in the 2011 sequence exceeded that of the previously documented largest microearthquake. Presence of faults that are close to failure and vulnerable to increase in pore pressure due to reservoir loading or increased rainfall, or a combination of both seems to trigger shocks in this area. The renewed burst of earthquakes after a prolonged period of reduced activity at the Idukki Reservoir is a rare example of RTS. (C) 2012 Elsevier B.V. All rights reserved.

Ages and relative sizes of pre-2004 tsunamis in the Bay of Bengal inferred from geologic evidence in the Andaman and Nicobar Islands

Geologic evidence along the northern part of the 2004 Aceh-Andaman rupture suggests that this region generated as many as five tsunamis in the prior 2000years. We identify this evidence by drawing analogy with geologic records of land-level change and the tsunami in 2004 from the Andaman and Nicobar Islands (A&N). These analogs include subsided mangrove swamps, uplifted coral terraces, liquefaction, and organic soils coated by sand and coral rubble. The pre-2004 evidence varies in potency, and materials dated provide limiting ages on inferred tsunamis. The earliest tsunamis occurred between the second and sixth centuries A.D., evidenced by coral debris of the southern Car Nicobar Island. A subsequent tsunami, probably in the range A.D. 770-1040, is inferred from deposits both in A&N and on the Indian subcontinent. It is the strongest candidate for a 2004-caliber earthquake in the past 2000years. A&N also contain tsunami deposits from A.D. 1250 to 1450 that probably match those previously reported from Sumatra and Thailand, and which likely date to the 1390s or 1450s if correlated with well-dated coral uplift offshore Sumatra. Thus, age data from A&N suggest that within the uncertainties in estimating relative sizes of paleo-earthquakes and tsunamis, the 1000year interval can be divided in half by the earthquake or earthquakes of A.D. 1250-1450 of magnitude >8.0 and consequent tsunamis. Unlike the transoceanic tsunamis generated by full or partial rupture of the subduction interface, the A&N geology further provides evidence for the smaller-sized historical tsunamis of 1762 and 1881, which may have been damaging locally.

Characterization of groundwater chemistry under the influence of lithologic and anthropogenic factors along a climatic gradient in Upper Cauvery basin, South India

Hydrogeological and climatic effect on chemical behavior of groundwater along a climatic gradient is studied along a river basin. `Semi-arid' (500-800 mm of mean annual rainfall), `sub-humid' (800-1,200 mm/year) and `humid' (1,200-1,500 mm/year) are the climatic zones chosen along the granito-gneissic plains of Kabini basin in South India for the present analysis. Data on groundwater chemistry is initially checked for its quality using NICB ratio (<+/- 5 %), EC versus TZ+ (similar to 0.85 correlation), EC versus TDS and EC versus TH analysis. Groundwater in the three climatic zones is `hard' to `very hard' in terms of Ca-Mg hardness. Polluted wells are identified (> 40 % of pollution) and eliminated for the characterization. Piper's diagram with mean concentrations indicates the evolution of CaNaHCO3 (semi-arid) from CaHCO3 (humid zone) along the climatic gradient. Carbonates dominate other anions and strong acids exceeded weak acids in the region. Mule Hole SEW, an experimental watershed in sub-humid zone, is characterized initially using hydrogeochemistry and is observed to be a replica of entire sub-humid zone (with 25 wells). Extension of the studies for the entire basin (120 wells) showed a chemical gradient along the climatic gradient with sub-humid zone bridging semi-arid and humid zones. Ca/Na molar ratio varies by more than 100 times from semi-arid to humid zones. Semi-arid zone is more silicaceous than sub-humid while humid zone is more carbonaceous (Ca/Cl similar to 14). Along the climatic gradient, groundwater is undersaturated (humid), saturated (sub-humid) and slightly supersaturated (semi-arid) with calcite and dolomite. Concentration-depth profiles are in support of the geological stratification i.e., not approximate to 18 m of saprolite and similar to 25 m of fracture rock with parent gneiss beneath. All the wells are classified into four groups based on groundwater fluctuations and further into `deep' and `shallow' based on the depth to groundwater. Higher the fluctuations, larger is its impact on groundwater chemistry. Actual seasonal patterns are identified using `recharge-discharge' concept based on rainfall intensity instead of traditional monsoon-non-monsoon concept. Non-pumped wells have low Na/Cl and Ca/Cl ratios in recharge period than in discharge period (Dilution). Few other wells, which are subjected to pumping, still exhibit dilution chemistry though water level fluctuations are high due to annual recharge. Other wells which do not receive sufficient rainfall and are constantly pumped showed high concentrations in recharge period rather than in discharge period (Anti-dilution). In summary, recharge-discharge concept demarcates the pumped wells from natural deep wells thus, characterizing the basin.

Lizard Wears Shades. A Spectacled Sphenomorphus (Squamata: Scincidae), from the Sacred Forests of Mawphlang, Meghalaya, North-east India

A new species of lygosomatine scincid lizard is described from the sacred forests of Mawphlang, in Meghalaya, northeastern India. Sphenomorphus apalpebratus sp. nov. possesses a spectacle or brille, an unusual feature within the Scincidae, and a first for the paraphyletic genus Sphenomorphus. The new species is compared with other members of the genus to which it is here assigned, as well as to members of the lygosomatine genera Lipinia and Scincella from mainland India, the Andaman and Nicobar Islands, and south-east Asia, to which it also bears resemblance. The new taxon is diagnosable in exhibiting the following combination of characters: small body size (SVL to 42.0 mm); moveable eyelids absent; auricular opening scaleless, situated in a shallow depression; dorsal scales show a line of demarcation along posterior edge of ventral pes; midbody scale rows 27-28; longitudinal scale rows between parietals and base of tail 62-64; lamellae under toe IV 8-9; supraoculars five; supralabials 5-6; infralabials 4-5; subcaudals 92; and dorsum golden brown, except at dorsal margin of lateral line, which is lighter, with four faintly spotted lines, two along each side of vertebral row of scales, that extend to tail base. The new species differs from its congeners in the lack of moveable eyelids, a character shared with several distantly related scincid genera.