Superrotation of upper atmosphere by global deposition of meteoroids

A new theory of the superrotation of upper atmosphere is worked out on the basis of global deposition of meteoroids assuming that a certain constant influx of meteoroids is continually falling upon the Earth's atmosphere. On the average the meteoroids are shown to carry a greater amount of orbital angular momentum than that corresponding to the Earth's orbit about the Sun. It is argued that the excess of orbital angular momentum appears as extra spin angular momentum in the atmospheric layer in which the meteoroids are arrested and this is used to calculate the velocity difference which can be maintained across a certain layer of the atmosphere. It is found that a global deposition of 34 tons/day of meteoric material is required to account for the observed superrotation which agrees with the recent estimates on meteoric mass influx on the Earth.     

Alkaline Magmatism Versus Collision Tectonics in the Eastern Ghats Belt, India: Constraints from Structural Studies in the Koraput Complex

Linear domains of deformed alkaline rocks and carbonatites have recently been identified as representing sites of ancient suture zones. In peninsular India, the western margin of the Proterozoic Eastern Ghats Belt (EGB) is characterized by a series of alkaline plutons that are aligned close to the contact with the Archaean Craton. Most of the complexes were deformed and metamorphosed during a subsequent orogenic event. Unlike other plutons in the belt, the alkaline complex at Koraput reportedly escaped deformation and granulite facies metamorphism forming an anomalous entity within the zone. Multiply-deformed country rocks hosting this complex underwent syn-D_1CR granulite facies metamorphism followed by D_2CR thrusting, with pervasive shearing along a NE-SW trending foliation. A second granulite facies event followed localized D_3CR shearing. Within the Koraput Complex, strain partitioning was responsible for preserving igneous textures in the gabbroic core, but aligned magmatic amphibole needles and plagioclase laths occasionally define a S_1AC fabric. Along the margins, S_1AC is rotated parallel to a NE-trending, east-dipping S_2AC fabric in the gabbro, fringing syenodiorite and nepheline syenite bands. Locally, D_3AC shearing follows D_2AC deformation; S_2AC and S_3AC parallel S_2CR and S_3CR in the country rocks. High-grade metamorphism represented by recrystallization of amphibole and plagioclase, and breakdown of amphibole and biotite to garnet, pyroxene and K-feldspar in the complex follows D_3AC. Unlike earlier reports, therefore, the Koraput body is also deformed and metamorphosed. The aligned alkaline complexes in the EGB probably represent deformed alkaline rocks and carbonatites formed by rifting related to an earlier episode of continental break-up that were deformed during subsequent juxtaposition of the EGB with the Archaean Craton. This supports the contention that the western margin of the EGB and its contact with the Archaean Craton is a suture zone related to the Indo-Antarctica collision event.     

Seasonal variation in the biochemical composition of red seaweed (<Emphasis Type="Italic">Catenella repens</Emphasis>) from Gangetic delta,northeast coast of India

The biochemical composition of red seaweeds, Catenella repens was investigated in this present study along with subsequent analysis of relevant physico-chemical variables. In this study, the relationship between the nutritive components of this species and the ambient environmental parameters was established. Protein content varied from 2.78 ± 0.30% of dry weight (stn.3) to 16.03 ± 0.96% of dry weight (stn.1) with highest values during monsoon. The protein levels were positively correlated with dissolved nitrate content and negatively correlated with water temperature (except stn.3) and salinity. Carbohydrate content of this species varied significantly (p < 0.05) during pre-monsoon between stations and the values showed positive relationship with salinity and surface water temperature. In contrast to carbohydrate, lipid concentration was lowest in values and varied very slightly between seasons and stations. Astaxanthin content of the seaweed species was greater in pre-monsoon than monsoon and post-monsoon in all the selected stations. Compared with the three seasons, samples of red seaweed collected in pre-monsoon has high carbohydrate-astaxanthin in contrast to protein-lipid which showed high values during monsoon. Statistical analysis computed among the environmental and biochemical parameters suggests the potential role played by the abiotic parameters on biosynthetic pathways of seaweed. This paper also highlights the influence of the nutritional quality of water that can be used for mass cultivation of Catenella repens.     

Probabilistic assessment of projected climatological drought characteristics over the Southeast USA

The study makes a probabilistic assessment of drought risks due to climate change over the southeast USA based on 15 Global Circulation Model (GCM) simulations and two emission scenarios. The effects of climate change on drought characteristics such as drought intensity, frequency, areal extent, and duration are investigated using the seasonal and continuous standard precipitation index (SPI) and the standard evapotranspiration index (SPEI). The GCM data are divided into four time periods namely Historical (1961–1990), Near (2010–2039), Mid (2040–2069), and Late (2070–2099), and significant differences between historical and future time periods are quantified using the mapping model agreement technique. Further, the kernel density estimation approach is used to derive a novel probability-based severity-area-frequency (PBS) curve for the study domain. Analysis suggests that future increases in temperature and evapotranspiration will outstrip increases in precipitation and significantly affect future droughts over the study domain. Seasonal drought analysis suggest that the summer season will be impacted the most based on SPI and SPEI. Projections based on SPI follow precipitation patterns and fewer GCMs agree on SPI and the direction of change compared to the SPEI. Long-term and extreme drought events are projected to be affected more than short-term and moderate ones. Based on an analysis of PBS curves, especially based on SPEI, droughts are projected to become more severe in the future. The development of PBS curves is a novel feature in this study and will provide policymakers with important tools for analyzing future drought risks, vulnerabilities and help build drought resilience. The PBS curves can be replicated for studies around the world for drought assessment under climate change.     

Changes in cosmic ray cut-off rigidities due to secular variations of the geomagnetic field

An analytical expression is derived for the cutoff rigidity of cosmic rays arriving at a point in an arbitrary direction, when the main geomagnetic field is approximated by that of an eccentric dipole. This expression is used to determine changes in geomagnetic cutoffs due to secular variation of the geomagnetic field since 1835. Effects of westward drift of the quadrupole field and decrease in the effective dipole moment are seen in the isorigidity contours. On account of the immense computer time required to determine the cutoff rigidities more accurately using the particle trajectory tracing technique, the present formulation may be useful in estimating the transmission factor of the geomagnetic field in cosmic ray studies, modulation of cosmogenic isotope production by geomagnetic secular variation, and the contribution of geomagnetic field variation to long term changes in climate through cosmic ray related modulation of the current flow in the global electric circuit.     

Hybrid Method for Love Wave Dispersion in Vertically Inhomogeneous Media

—Love wave dispersion in a vertically inhomogeneous multilayered medium is studied by a combination of analytical and numerical methods for arbitrary variation of rigidity and density with depth. The problem is reduced to a boundary value problem for a differential equation and solved numerically. The method compares favourably with other methods in use. Simple particular cases are considered and interesting results are exhibited graphically.     

Statistical improvement in detection level of gravitational microlensing events from their light curves

In astronomy,the brightness of a source is typically expressed in terms of magnitude.Conventionally,the magnitude is defined by the logarithm of received flux.This relationship is known as the Pogson formula.For received flux with a small signal to noise ratio(S/N),however,the formula gives a large magnitude error.We investigate whether the use of Inverse Hyperbolic Sine function(hereafter referred to as the Asinh magnitude)in the modified formulae could allow for an alternative calculation of magnitudes for small S/N flux,and whether the new approach is better for representing the brightness of that region.We study the possibility of increasing the detection level of gravitational microlensing using 40 selected microlensing light curves from the 2013 and 2014 seasons and by using the Asinh magnitude.Photometric data of the selected events are obtained from the Optical Gravitational Lensing Experiment(OGLE).We found that utilization of the Asinh magnitude makes the events brighter compared to using the logarithmic magnitude,with an average of about 3.42×10~(-2)magnitude and an average in the difference of error between the logarithmic and the Asinh magnitude of about 2.21×10(-2)magnitude.The microlensing events OB140847 and OB140885 are found to have the largest difference values among the selected events.Using a Gaussian fit to find the peak for OB140847 and OB140885,we conclude statistically that the Asinh magnitude gives better mean squared values of the regression and narrower residual histograms than the Pogson magnitude.Based on these results,we also attempt to propose a limit in magnitude value for which use of the Asinh magnitude is optimal with small S/N data.     

A connectionist approach to SODAR pattern classification

SODAR (or acoustic radar) systems are a useful tool to efficiently probe the lower planetary boundary layer (LPBL). The observations obtained by these systems can prove to be extremely useful if classified and interpreted correctly. The manual identification of different types of SODAR-recorded lower atmospheric microstructures is a laborious task and can be performed only by an expert having wide experience with the system and the variety of observations recorded by it. In this letter, we have developed a connectionist system to classify or identify SODAR patterns. The results demonstrate that the multilayer perceptron-based model is capable of successfully identifying the different SODAR patterns.     

Effects of estuarine organic matter biogeochemistry on the bioaccumulation of PAHs by two epibenthic species

Polycyclic aromatic hydrocarbon (PAH) biota-sediment accumulation factors (BSAF) were quantified in sediments from two sites in southeastern Louisiana in a 14 d microcosm study usingPalaemonetes pugio, andRangia cuneata and two radiolabeled PAHs, phenanthrene and benzo[a]pyrene (b[a]p). For both PAHs studied, mean BSAFs were significantly higher (p<0.0001) in both organisms in sediments from Bayou Trepagnier, (BSAF=0.628 g OC g TLE⁻¹), a brackish swamp, compared to Pass Fourchon (0.065 g OC g TLE⁻¹), a coastal salt marsh. In order to explain observed patterns in BSAFs, organic carbon-normalized PAH distribution coefficients between the sediment and freely dissolved phases (K_OC)_OBS were determined as well as the various geochemical variables of particulate and dissolved organic matter (POM and DOM, respectively). These included analyses of particle surface area, total organic carbon (TOC), carbon to nitrogen ratios (C∶N), and dissolved organic carbon (DOC). Bayou Trepagnier was higher in surface area, TOC, C∶N, as well as DOC suggesting that the difference in BSAFs may be attributed to compositional differences in POM and DOM between sites. We can not exclude the possibility that other factors (such as differences in organism behavior resulting from contrasting sediment characteristics) were responsible for BSAFs varying between the two sites. Phenanthrene BSAFs were typically higher than b[a]p BSAFs, suggesting contaminants were limited in their desorption from sediment particles as a function of PAH molecular weight. Mean BSAFs for both PAHs were higher on Day 7 than on Day 14. The reason for this decrease is unclear, but did not appear to be due to organisms becoming increasingly stressed in the microcosms. Visual observations indicated that animals remained feeding while no decreases in organism total lipid levels were detected. The trends in BSAFs between sites and over the time course of this experiment suggest that contaminant bioaccumulation in estuarine systems should not be considered to be an equilibrium process.