Seasonal discharge and chemical flux variations of rivers flowing into the Bayhead canal of Durban Harbour,South Africa

The u Mhlatuzana, u Mbilo and a Manzimnyama river catchments located on the eastern seaboard of the Kwa Zulu-Natal province, South Africa, form the core of urbanization and industrialization, contributing the only natural freshwater inflows to the Bayhead Canal portion of the Durban Harbour. In this study, seasonal discharges and physico–chemical water properties were used to quantitatively determine the material mass transport capacity of the river systems on the basis of hydrographic inputs and chemical loading from the surrounding land use sectors.The mass transport of the total dissolved solids（TDS）,ammonia（NH₄）, phosphorous（P）, aluminum（Al）, calcium（Ca）, copper（Cu）, chromium（Cr）, mercury（Hg）, potassium（K）, magnesium（Mg）, sodium（Na）, nickel（Ni）, lead（Pb）, sulphur（S） and vanadium（V） was determined for each river. Results indicated that land use, seasonality and river flow were significant determinants for the material loading in the rivers and the receiving port waters. The spatio-temporal distribution patterns of chemical fluxes indicated that industrial activity associated with the a Manzimnyama canal contributed the most, with regards to TDS, NH₄, Ca, K, Mg, Na, S and V, loading in both wet and dry seasons, as well as Al, Cu, Hg and Pb during the dry season. Similarly, industrial activity associated with the u Mbilo/u Mhlatuzana Canal at the lower reaches accounted for the highest P, Al, Cu and Pb fluxes in the wet season alone. Fluxes of these parameters are used to explain theobserved elemental concentrations and patterns of the receiving port waters of the Bayhead Canal.     

Pioneer Venus Orbiter Measurements of Solar EUV Flux During Solar Cycles 21 and 22

The Pioneer Venus Orbiter (PVO) had on board the electron temperature probe experiment which measured temperature and concentration of electrons in the ionosphere of Venus. When the probe was outside the Venus ionosphere and was in the solar wind, the probe current was entirely due to solar photons striking the probe surface. This probe thus measured integrated solar EUV flux (Ipe) over a 13-year period from January 1979 to December 1991, thereby covering the declining phase of solar cycle 21 and the rising phase of solar cycle 22. In this paper, we examine the behavior of Ipe translated to the solar longitude of Earth (to be called EIpe) during the two solar cycles. We find that total EUV flux changed by about 60% during solar cycle 21 and by about 100% in solar cycle 22. We also compare this flux with other solar activity indicators such as F_10.7 , Lα, and the solar magnetic field. We find that while the daily values of EIpe are highly correlated with F_10.7 (correlation coefficient 0.87), there is a large scatter in EIpe for any value of this Earth-based index. A comparison of EIpe with SME and UARS SOLSTICE Lα measurements taken during the same period shows that EIpe tracks Lα quite faithfully with a correlation coefficient of 0.94. Similar comparison with the solar magnetic field (Bs) shows that EIpe correlates better with Bs than with F_10.7 . We also compare EIpe with total solar irradiance measured during the same period.     

Performance analysis of different predictive models for crop classification across an aridic to ustic area of Indian states

The purpose of this study is to present comparative performance analysis of different machine learning algorithms for large area crop classification. Ten Indian districts with significant rabi crops viz. wheat, mustard, gram, red lentils (masoor) have been selected for the study. Most popular classical ensemble models – bagging/ARCing, random forest (RF), gradient boosting and Importance Sampled Learning Ensemble (ISLE) with traditional single model (decision tree) have been selected for comparative analysis. To incorporate dependency of large area crop in different variables viz. parent material and soil, phenology, texture, topography, soil moisture, vegetation, climate etc., 35 digital layers are prepared using different satellite data (ALOS DEM, Landsat-8, MODIS NDVI, RISAT-1, Sentinental-1A) and climatic data (precipitation, temperature). In rabi season, field survey about crop type is carried out to prepare training data. Performance is evaluated on the basis of marginal rates, F-measure and Jaccard’s coefficient of community, Classification Success Index and Agreement Coefficients. Score is calculated to rank the algorithm. RF is best performer followed by gradient boosting for crop classification. Other ensemble methods ARCing, bagging and ISLE are in decreasing order of performance. Traditional non-ensemble method decision tree scored higher than ISLE.     

Significance of assimilation and fractional crystallization (AFC) process in the generation of basaltic lava flows from Chhotaudepur area,Deccan Large Igneous Province,NW India

Basaltic and basaltic andesitic flows have been identified from the Chhotaudepur area in the Deccan Large Igneous Province. The \(\hbox {SiO}_{2}\) content of these flows varies from 46.7 to 53.7 wt%. None of the samples have primary magma signatures as they exhibit low Mg# (0.42–0.68), Ni (4.8–33.4 ppm) and Cr (33.08–143.06 ppm). Highly variable concentrations of the LILE [Rb (2–74 ppm), Ba (52–351 ppm), Cs (0.1–1 ppm) and Sr (273–745 ppm)] and relatively enriched LREE are also noticed. The coherent chondrite normalized REE diagram and primitive mantle normalized multi-element diagram suggests a consanguinity among the flows. Low (Nb/Th)\(_{\mathrm{PM}}\) (0.30–1.09), high (Th/Yb)\(_{\mathrm{PM}}\) (3.09–16.58) ratios and marked variations in Rb concentration (2.4–74.11 ppm) with variable La/Yb (5.5–23.7) ratios suggests that magmas in the Chhotaudepur region were assimilated by the crustal components. The elevated Th/Ta and La/Yb relation further indicate concurrent assimilation and fractional crystallization process was involved in the genesis of the flows. Assimilation and fractional crystallization modelling of the flows was carried out with 20% olivine, 25% clinopyroxene, 45% plagioclase and 10% titano-magnetite as fractionating minerals and upper continental crust as the assimilant. The results reveal that all the flows were modified by AFC process.     

Generalized dual porosity: A numerical method for representing spatially variable sub-grid scale processes

A generalized dual porosity method (GDPM) has been developed to incorporate sub-grid scale heterogeneity into large-scale flow and transport simulations. The method is spatially variable in the sense that the method can be applied with different levels of resolution for different spatial nodes in the simulation. The method utilizes the nodal connectivity structure and linear equation solvers of unstructured grids like those used in the finite element method, and can be applied to any problem without externally modifying the numerical grid. The algorithm scales linearly in CPU time and storage with the number of GDPM nodes. We demonstrate the utility and computational efficiency of the technique with two verification problems and an example problem of a field site.     

Topology of Rayleigh–Bénard convection and magnetoconvection in plane layer

ABSTRACT

The present study aims to link the dynamics of geophysical fluid flows with their vortical structures in physical space and to study the transition of these structures due to the control parameters. The simulations are carried in a rectangular box filled with liquid gallium for three different cases, namely, Rayleigh–Bénard convection (RBC), magnetoconvection (MC) and rotating magnetoconvection (RMC). The physical setup and material properties are similar to those considered by Aurnou and Olson in their experimental work. The simulated results are validated with theoretical results of Chandrasekhar and experimental results of Aurnou and Olson. The results are also topologically verified with the help of Euler number given by Ma and Wang. For RBC, the onset is obtained at Ra greater than 1708 and at this Ra, the symmetric rolls are orientated in/along a horizontal axis. As the value of Ra increases further, the width of the horizontal rolls starts to amplify. It is observed that these two-dimensional rolls are nothing but the cross-sections of three-dimensional (3D) cylindrical rolls with wave structures. When the vertically imposed magnetic field is added to RBC, the onset of convection is delayed due to the effect of Lorentz force on the thermal buoyancy force. The presence of 3D rectangular structures is highlighted and analysed. When the magnetically influenced rectangular box rotates about vertical axis at low rotation rates in magnetoconvection model, the onset of convection gets further delayed by magnetic field, which is in general agreement with the theoretical predictions. The critical Ra increases linearly with magnetic field intensity. Coherent thermal oscillations are detected near the onset of convection, at moderate rotation rates.     

Spatial distribution of grain size and depositional process in tidal area along Waikelo Beach,Sumba

A study of characteristics and distribution of sediment along Waikelo Beach, Sumba, Nusa Tenggara Timur (NTT), Indonesia has been conducted using grain size train analysis. Grain size train analysis aims to determine physical properties and textural parameters such as mean, sorting, skewness, and kurtosis. Samples were taken from several locations on the beach that represent high-tide, transition, and low-tide areas. The observation of two physical characteristics has concluded two points: (1) changing in textural pattern that shows physical differences of sediments is a result of interaction between deposition process and marine activities; (2) the abundance of coarse to medium sand demonstrates general process of sediment deposition along Waikelo Beach deposited at moderate to low energy. Linear discriminate function indicates aeolian, shallow marine, and fluvial environments. CM diagram (C?=?one percentile in micron, M?=?median in micron) describes the mechanism of sediment deposition on the beach in rolling and ground suspension. These all conditions are supported by the plotting results in the Stewart diagram that shows the influence of current either from waves or from river.     

Implications of geochemistry in support of Palaeo-Proterozoic tectonothermal evolution of bhopalpatnam Granulite Belt, Bastar Craton, Central India

Bhopalpatnam Granulite Belt which occur along SW margin of Bastar Craton and NE shoulder of Pranhita-Godavari Rift comprise of charnockite (enderbitic variety), garnet-sillimanite-biotite gneiss, quartzo-feldspathic gneiss and corundum bearing aluminous gneiss. High La/Yb ratio, low Eu anomaly (Eu/Eu*=1.0), high LREE/HREE ratio with uniform REE pattern, high La/Sc ratio (0.53–6.43), high Th/Sc ratio (0.03–2.56), low Ni (5.52–20.95), low Cr (31.05–117.05) and uniform Zr/Hf distribution pattern indicate a Proterozoic character. Distribution pattern of K₂O, Na₂O and CaO in ternary diagram show quartz-monzonite-granodiorite trend for the bulk rocks indicating that the bulk rock composition is close to TTG of early Archaean, which might have supplied the sediments for the rocks of Bhopalpatnam Granulite Belt. Geochemical and mineralogical evidence indicate an argillaceous protolith for garnet — sillimanite — biotite gneiss and corundum bearing aluminous gneiss, whereas an arkosic protolith for quartzo-feldspathic gneiss. The geochemical signatures also suggest an active continental margin setting for the rocks of Bhopalpatnam Granulite Belt with prominent Nb and Ta anomaly favouring a subduction environment between Bastar Craton and East Dharwar Craton. This is in conformity with the finding of the earlier workers suggesting a clockwise P-T path based on the combined fluid inclusion and mineral phase equilibria. The LILE geochemistry of charnockite suggests a bi-phase evolution. High LREE/HREE ratio portrays a highly evolved nature of the charnockitic melt generated through partial melting of the continental crust at the final stage of the granulite facies metamorphism during collision between Bastar and East Dharwar Cratons.