A comparative study of the Indian summer monsoon hydroclimate and its variations in three reanalyses

This study examines the Indian summer monsoon hydroclimate in the National Centers for Environmental Prediction (NCEP)-Department of Energy (DOE) Reanalysis (R2), the Climate Forecast System Reanalysis (CFSR), and the Modern Era Retrospective-Analysis for Research and Applications (MERRA). The three reanalyses show significant differences in the climatology of evaporation, low-level winds, and precipitable water fields over India. For example, the continental evaporation is significantly less in CFSR compared to R2 and MERRA. Likewise the mean boreal summer 925?hPa westerly winds in the northern Indian Ocean are stronger in R2. Similarly the continental precipitable water in R2 is much less while it is higher and comparable in MERRA and CFSR. Despite these climatological differences between the reanalyses, the climatological evaporative sources for rain events over central India show some qualitative similarities. Major differences however appear when interannual variations of the Indian summer monsoon are analyzed. The anomalous oceanic sources of moisture from the adjacent Bay of Bengal and Arabian Sea play a significant role in determining the wet or dry year of the Indian monsoon in CFSR. However in R2 the local evaporative sources from the continental region play a more significant role. We also find that the interannual variability of the evaporative sources in the break spells of the intraseasonal variations of the Indian monsoon is stronger than in the wet spells. We therefore claim that instead of rainfall, evaporative sources may be a more appropriate metric to observe the relationship between the seasonal monsoon strength and intraseasonal activity. These findings are consistent across the reanalyses and provide a basis to improve the predictability of intraseasonal variability of the Indian monsoon. This study also has a bearing on improving weather prediction for tropical cyclones in that we suggest targeting enhanced observations in the Bay of Bengal (where it is drawing the most moisture from) for improved analysis during active spells of the intraseasonal variability of the Indian monsoon. The analysis suggests that the land–atmosphere interactions contribute significant uncertainty to the Indian monsoon in the reanalyses, which is consistent with the fact that most of the global reanalyses do not assimilate any land-surface data because the data are not available. Therefore, the land–atmosphere interaction in the reanalyses is highly dependent on the land-surface model and it’s coupling with the atmospheric model.     

Litho-tectonic sequence and their regional correlation along the Lohit and Dibang valleys,eastern Arunachal Pradesh

Geological mapping between Lohit and Dibang valleys of eastern Arunachal Pradesh reveals the existence of five thrust bound tectonostratigraphic units. In ascending structural order from SW to NE these are: (1) Sewak Group, (2) Lalpani Group, (3) Mayodiya Group, (4) Tidding Formation and (5) Lohit plutonic complex. This differs from previous mapping, because the three tectonostratigraphic units (Sewak, Lalpani and Mayodiya) were grouped under a single unit, referred as the Mishmi crystallines. The low-grade metamorphics of the Sewak Group occur at two different tectonic levels, one as persistent belt in the foothills and the other in the tectonic window beneath the high-grade metamorphics of the Mayodiya thrust sheet in the Higher Himalaya. The Tidding suture is the southeastern extension of the Indus-Tsangpo suture zone.     

Erratic shortening from balanced cross-sections of the western Himalayan foreland basin: causes and implications for basin evolution

Balanced cross-sections from the western Himalayan foreland foothill belt reveal a variation in shortening amounts from 22 to 71.3% over a lateral distance of 85 km. The large variation may be attributed to the fact that the method of cross-section balancing considers the initial layering as horizontal, which is an unlikely situation in foreland basins. Simple trigonometric relationships are used to minimize the error in shortening estimates. However, the suggested corrections could not be applied to the Himalayan foreland basin because of unavailability of the required data on initial basin geometry. The study also indicates that shortening rates for the area based on these shortening amounts cannot be used for earthquake prediction.     

Lineaments and tectonic analysis through landsat imagery and its implications on the evaluation of bauxite and laterite deposits in and around Panchpatmali area,Koraput District,Orissa

Lineaments of Panchpatmali plateau and the adjoining areas in Koraput District, Orissa, lying on the East Coast of India, were analysed to elucidate their influence on the occurrence of’ laterite/bauxite duricrust of the area. A detailed lineament map and a map of the explored and expected deposits of laterite and bauxite of the areas have been prepared from satellite imagery after ‘Band Ratioing’ and ‘Maximum Likelihood Classification’ and ground truth study. Development of laterite/bauxite plateaus follows the regional lineament trend of NE - SW, probably due to the tectonic activities in the area. It has been observed that there are atleast two major planation surfaces - the older one shows complete development of laterite/bauxite duricrust, whereas the younger planation surfaces are devoid of any.     

Verification of a shore-line dispersion model for continuous fumigation

This paper describes the verification of a dispersion model for a shoreline environment developed by the author in an earlier paper. It is shown that the observed concentration field reported in a case study agrees well with model predictions. Emphasis has been given to verification of the location of the maximum ground-level concentration and the downwind trend of the concentration field. This is because time-averaged concentrations are dependent on averaging time. Since a model generally predicts ensemble average concentrations which may not be achieved within half-hour periods within a convective boundary layer, numerical comparisons may not be very meaningful. Nevertheless, good agreement is found for the case study under consideration.     

Palaeoclimate,stratigraphy and prehistory in north and west Rajasthan

Quaternary formations in western Rajasthan are of fluvial, locustrinal and aeolian origins. Fossil gravel ridge of Jayal in Nagaur District is one of the earliest quaternary formations so far recorded in the region. A rich lower palaeolithic habitation-cum-workshop site has been discovered in association with the gravel ridge. Multiple evidence for climatic change in the area during the quaternary period is discussed.     

Analytical solution for micropile design under tension and compression

Micropiles are being increasingly utilized in foundation rehabilitation and seismic retrofitting projects. The function of the micropiles in these projects is to enhance the foundation ultimate capacity as well as reduce foundation deflection. This paper focuses on an analytical model for micropile load-displacement behavior subjected to compressive as well as tensile loading. The soil-micropile interaction is considered explicitly in the model development. Furthermore, to keep the model simple and accessible to designers, the micropile-soil interface is assumed to be linearly elastic-perfectly plastic and homogeneous with depth. Closed form expressions of micropile deformation as a function of applied load are presented. These expressions are used to study the effect of model parameters on micropile yield behavior. Micropile strain distribution and the load transfer behavior calculated by the model are discussed. The model calculations are compared with the field measured load-displacement curves. The measured micropile load-displacement data available in the literature are analyzed to evaluate the model parameters. This revised version was published online in July 2006 with corrections to the Cover Date.     

Nature of diamonds in Yakutian eclogites: views from eclogite tomography and mineral inclusions in diamonds

We have performed dissections of two diamondiferous eclogites (UX-1 and U33/1) from the Udachnaya kimberlite, Yakutia in order to understand the nature of diamond formation and the relationship between the diamonds, their mineral inclusions, and host eclogite minerals. Diamonds were carefully recovered from each xenolith, based upon high-resolution X-ray tomography images and three-dimensional models. The nature and physical properties of minerals, in direct contact with diamonds, were investigated at the time of diamond extraction. Polished sections of the eclogites were made, containing the mould areas of the diamonds, to further investigate the chemical compositions of the host minerals and the phases that were in contact with diamonds. Major- and minor-element compositions of silicate and sulfide mineral inclusions in diamonds show variations among each other, and from those in the host eclogites. Oxygen isotope compositions of one garnet and five clinopyroxene inclusions in diamonds from another Udachnaya eclogite (U51) span the entire range recorded for eclogite xenoliths from Udachnaya. In addition, the reported compositions of almost all clinopyroxene inclusions in U51 diamonds exhibit positive Eu anomaly. This feature, together with the oxygen isotopic characteristics, is consistent with the well-established hypothesis of subduction origin for Udachnaya eclogite xenoliths. It is intuitive to expect that all eclogite xenoliths in a particular kimberlite should have common heritage, at least with respect to their included diamonds. However, the variation in the composition of multiple inclusions within diamonds, and among diamonds, from the same eclogite indicates the involvement of complex processes in diamond genesis, at least in the eclogite xenoliths from Yakutia that we have studied.     

Measured kinematic fields in the biaxial shear of granular materials

Biaxial experiments are performed with rod assemblies to study the micro-mechanical deformation behavior of granular materials. The focus of these experiments is upon the micromechanical behavior under mixed boundary conditions, with stress-controlled lateral boundaries and displacement-controlled axial boundaries. Particle motions, i.e. displacements and rotations, are measured during the test. The particle motions are analyzed to study deformation patterns, including shear localization. Deformation patterns in a number of rod assemblies with random packing structures are investigated.