Nowcasting Bordoichila with a composite stability index

In operational forecast, the stability indices either individually or in combination are utilized to assess the predictability of local severe storms over a region. The objective of the present study is to identify such stability indices to assess the predictability of Bordoichila of Guwahati, India, during the pre-monsoon season (April–May) aiming to formulate a composite stability index using the most pertinent indices for nowcasting Bordoichila with considerable precision. Bordoichila, meaning the angry daughter of Assam, represents local severe storms of Guwahati during the pre-monsoon season. Precise forecast of Bordoichila is essential to mitigate the associated catastrophe over Guwahati. The forecast quality detection parameters are computed with the available indices during the period from 1997 to 2006 to select the most relevant stability indices for the prevalence of Bordoichila. The method of normal probability distribution is implemented to identify the threshold ranges of the selected indices. The stability indices that are selected with appropriate ranges are lifted index, Showalter index (SI), cross total index (CTI), vertical total index, totals total, convective available potential energy, convective inhibition energy, SWEAT and bulk Richardson number. The forecast skill scores are estimated with the selected indices. The best predictor indices identified for the prevalence of Bordoichila are the cross total index (CTI) and Showalter index (SI). A composite stability index, Bordoichila prediction index, is formulated with CTI and SI with proper weightages. The forecast with BPI is validated with the observations of India Meteorological Department for the year 2007 and is implemented for real-time forecast for the years 2009 and 2011.     

Higher order corrections to dust-acoustic ZK-solitons in a magnetized quantum dusty plasma

Nonlinear propagation of two dimensional dust-acoustic solitary waves in a magnetized quantum dusty plasma whose constituents are electrons, ions, and negatively charged heavy dust particles are investigated using quantum hydrodynamic model. The Zakharov-Kuznetsov (ZK) equation is derived by using reductive perturbation technique (RPT). The higher order inhomogeneous ZK-type differential equation is obtained for the correction to ZK- soliton. The dynamical equation for dressed soliton is solved by using renormalization method. The effects of obliqueness (l _x ) of the wave vector, magnetic field strength (B ₀), quantum parameter for ions (H _i ), soliton velocity (θ) and Fermi temperature ratio (σ) on amplitudes and widths of the ZK-soliton and as well as of the dressed soliton are investigated. The conditions for the validity of the higher order correction are described. Suitable parameter ranges for the existence of compressive and rarefactive dressed solitons are also discussed.     

Hydraulic redistribution by deeply rooted grasses and its ecohydrologic implications in the southern Great Plains of North America

Perennial bioenergy crops with deep (>1 m) rooting systems, such as switchgrass (Panicum virgatum L.), are hypothesized to increase carbon storage in deep soil. Deeply rooted plants may also affect soil hydrology by accessing deep soil water for transpiration, which can affect soil water content and infiltration in deep soil layers, thereby affecting groundwater recharge. Using stable H and O isotope (δ²H and δ¹⁸O) and ³H values, we studied the soil water conditions at 20–30 cm intervals to depths of 2.4–3.6 m in paired fields of switchgrass and shallow rooted crops at three sites in the southern Great Plains of North America. We found that soil under switchgrass had consistently higher soil water content than nearby soil under shallow-rooted annual crops by a margin of 15%–100%. Soil water content and isotopic depth profiles indicated that hydraulic redistribution of deep soil water by switchgrass roots explained these observed soil water differences. To our knowledge, these are the first observations of hydraulic redistribution in deeply rooted grasses, and complement earlier observations of dynamic soil water fluxes under shallow-rooted grasses. Hydraulic redistribution by switchgrass may be a strategy for drought avoidance, wherein the plant may actively prevent water limitation. This raises the possibility that deeply rooted grasses may be used to passively subsidize soil water to more shallow-rooted species in inter-cropping arrangements.     

On magnetoelastic disturbances in an aelotropic elastic cylinder placed in a magnetic field

Summary The present note deals with the disturbances in an aelotropic elastic cylinder placed in an axial magnetic field, being acted upon by a mechanical force.     

The significance of rubidium-strontium age of sedimentary rock

The isotopic composition of strontium and the rubidium and strontium contents were measured for samples of the Lower Permian Havensville Shale collected at four different localities across a distance of approximately 200 miles in Kansas and northern Oklahoma. The Rb-Sr dates ranged from 320 m.y. to 395 m.y. The initial Sr⁸⁷/Sr⁸⁶ ratios were between 0.709 and 0.717. The ages are interpreted to be intermediate between the age of the source material and the time of sedimentation and, therefore, are not indicative of any geologic event. A model has been proposed to explain the colinearity of the Rb-Sr data and the evolution of different Rb-Sr dates for the same stratigraphic unit at different localities.     

Rare-earths in size fractions and sedimentary rocks of Pennsylvanian-Permian age from the mid-continent of the U.S.A.

The REE (rare-earth) contents of sixty-three <2 μ fractions of Pennsylvanian and Permian platform sediment from the mid-continent of the U.S.A. vary considerably (ΣREE = 46–439 ppm;La/ Lu = 5.2–15.7; correlation coefficient of REE with La/Lu = 0.89), but the Eu/Sm ratios are nearly constant even in reducing environments that concentrate U (0.16–0.22). There is no correlation of REE content to clay mineralogy.Lower Permian <2 μ fractions from continental to nearshore marine sediment in Oklahoma have higher REE content (244–261 ppm) than marine facies in Kansas (46–140ppm), but <2μ Upper Permian fractions in an evaporite basin have constant but high REE content (288–281 ppm; one = 153—ppm). All Pennsylvanian <2 μ fractions from Oklahoma have high REE content (209–439 ppm), and fractions from Kansas cyclothems have variable REE content (86–438 ppm). REE content in the <2 μ fractions is inherited from the provenance, but is modified by ion exchange during weathering, transportation, or deposition. Exchangable REE tend to be concentrated in clay minerals in basic environments, but removed in acid environments.Sand and gravel-size fractions consist mostly of quartz or chert so their REE content is low (7.9–40.6 ppm) although heavy minerals may contribute a large fraction of the REE content. Unexpectedly, silt-size fractions have REE contents (74–355 ppm) that are usually lower but similar to their <2 μ fractions, and the REE contents do not correlate to clay mineral/quartz ratios. The interpretation of REE content in sedimentary rocks needs to be done cautiously due to the above factors.     

Relationship of chemical fractions of heavy metals with microbial and enzyme activities in sludge and ash-amended acid lateritic soil from India

The influence of metals, Cd, Cr, Cu, Ni, Pb and Zn, on the microbial biomass and enzyme activities of an amended acid lateritic soil were investigated under field conditions receiving a one-time application of 52 t ha^–1 of sludge, coal ash and their mixtures at 1:3, 1:1 and 3:1 proportions, and including control and chemical fertilizer treatment at crop-specific recommended doses. Paddies and peanuts were grown in the experimental plots and soil was sampled twice after 6 months and 1 year after amendment application. The heavy metals in the soil were fractionated using sequential extraction and the increments in their concentrations in amended soil with respect to the control were determined. Concentrations of Cd, Ni and Zn were determined to have increased in their mobile fractions and were more pronounced in soil collected during the second sampling, which was associated with a decrease in soil organic carbon. The size of the microbial biomass carbon and the soil enzyme activities increased with the addition of an amendment and was highest at equal proportions of coal ash and sludge. Further increase in the proportion of sludge resulted in a significant decrease in biomass carbon. Simple correlation revealed significant and strong negative relations of mobile fractions of Cd and Ni with the ratio between microbial biomass C and organic carbon in soil, while the organic carbon content and the pH were positively correlated. The microbial activities were determined to be sensitive to the concentrations of some heavy metals in mobile fractions and therefore indicated possibilities of being useful as indicators for evaluation of toxic effects of sludge-borne metals on soil organisms.     

Mineralogy and petrology of cretaceous subsurface lamproite sills, southeastern Kansas, USA

Cores and cuttings of lamproite sills and host sedimentary country rocks in southeastern Kansas from up to 312 m depth were analyzed for major elements in whole rocks and minerals, certain trace elements in whole rocks (including the REE) and Sr isotopic composition of the whole rocks. The lamproites are ultrapotassic (K₂O/Na₂O = 2.0–19.9), alkalic [molecular (K₂O/Na₂O)/Al₂O₃ = 1.3-2.8], enriched in mantle-incompatible elements (light REE, Ba, Rb, Sr, Th, Hf, Ta) and have nearly homogeneous initial Sr isotopic compositions (0.707764-0.708114).

These lamproites could have formed by variable degrees of partial melting of harzburgite country rock and cross-cutting veins composed of phlogopite, K-Ti richterite, titanite, diopside, K-Ti silicates, or K-Ba-phosphate under high H₂O/CO₂ ratios and reducing conditions. Variability in melting of veins and wall rock and variable composition of the metasomatized veins could explain the significantly different composition of the Kansas lamproites.

Least squares fractionation models preclude the derivation of the Kansas lamproites by fractional crystallization from magmas similar in composition to higher silica phlogopite-sanidine lamproites some believe to be primary lamproite melts found elsewhere. In all but one case, least squares fractionation models also preclude the derivation of magmas similar in composition to any of the Kansas lamproites from one another. A magma similar in composition to the average composition of the higher SiO₂ Ecco Ranch lamproite (237.5–247.5 m depth) could, however, have marginally crystallized about 12% richterite, 12% sanidine, 7% diopside and 6% phlogopite to produce the average composition of the Guess lamproite (305–312 m depth).

Lamproite from the Ecco Ranch core is internally fractionated in K₂O, Al₂O₃, Ba, MgO, Fe₂O₃, Co and Cr most likely by crystal accumulation-removal of ferromagnesian minerals and sanidine. In contrast, the Guess core (305–312 m depth) has little fractionation throughout most of the sill except in several narrow zones. Lamproite in the Guess core has large enrichments in TiO₂, Ba, REE, Th, Ta and Sc and depletions in MgO, Cr, Co and Rb possibly concentrated in these narrow zones during the last dregs of crystallization of this magma.

The Ecco Ranch sill did not show any evidence of loss of volatiles or soluble elements into the country rock. This contrasts to the previously studied, shallow Silver City lamproite which did apparently lose H₂O-rich fluid to the country rock. Perhaps a greater confining pressure and lesser amount of H₂O-rich fluid prevented it from escaping.     

Sedimentary facies and soft-sediment deformation structures in the late miocene-pliocene Middle Siwalik subgroup,eastern Himalaya,Darjiling District,India

The Himalayan fold-and-thrust belt has propagated from its Tibetan hinterland to the southern foreland since ∼55 Ma. The Siwalik sediments (∼20 - 2 Ma) were deposited in the frontal Himalayan foreland basin and subsequently became part of the thrust belt since ∼ 12 Ma. Restoration of the deformed section of the Middle Siwalik sequence reveals that the sequence is ∼325 m thick. Sedimentary facies analysis of the Middle Siwalik rocks points to the deposition of the Middle Siwalik sediments in an alluvial fan setup that was affected by uplift and foreland-ward propagation of Greater and Lesser Himalayan thrusts. Soft-sediment deformation structures preserved in the Middle Siwalik sequence in the Darjiling Himalaya are interpreted to have formed by sediment liquefaction resulting from increased pore-water pressure probably due to strong seismic shaking. Soft-sediment structures such as convolute lamination, flame structures, and various kinds of deformed cross-stratification are thus recognized as palaeoseismic in origin. This is the first report of seismites from the Siwalik succession of Darjiling Himalaya which indicates just like other sectors of Siwalik foreland basin and the present-day Gangetic foreland basin that the Siwalik sediments of this sector responded to seismicity.