Downscaling future climate change projections over Puerto Rico using a non-hydrostatic atmospheric model

We present results from 20-year “high-resolution” regional climate model simulations of precipitation change for the sub-tropical island of Puerto Rico. The Japanese Meteorological Agency Non-Hydrostatic Model (NHM) operating at a 2-km grid resolution is nested inside the Regional Spectral Model (RSM) at 10-km grid resolution, which in turn is forced at the lateral boundaries by the Community Climate System Model (CCSM4). At this resolution, the climate change experiment allows for deep convection in model integrations, which is an important consideration for sub-tropical regions in general, and on islands with steep precipitation gradients in particular that strongly influence local ecological processes and the provision of ecosystem services. Projected precipitation change for this region of the Caribbean is simulated for the mid-twenty-first century (2041–2060) under the RCP8.5 climate-forcing scenario relative to the late twentieth century (1986–2005). The results show that by the mid-twenty-first century, there is an overall rainfall reduction over the island for all seasons compared to the recent climate but with diminished mid-summer drought (MSD) in the northwestern parts of the island. Importantly, extreme rainfall events on sub-daily and daily time scales also become slightly less frequent in the projected mid-twenty-first-century climate over most regions of the island.     

Cosmic-ray positrons: are there primary sources?

Galactic cosmic rays consist of primary and secondary particles. Primary cosmic rays are thought to be energized by first order Fermi acceleration processes at supernova shock fronts within our Galaxy. The cosmic rays that eventually reach the Earth from this source are mainly protons and atomic nuclei, but also include electrons. Secondary cosmic rays are created in collisions of primary particles with the diffuse interstellar gas. They are relatively rare but carry important information on the Galactic propagation of the primary particles. The secondary component includes a small fraction of antimatter particles, positrons and antiprotons. In addition, positrons and antiprotons may also come from unusual sources and possibly provide insight into new physics. For instance, the annihilation of heavy supersymmetric dark matter particles within the Galactic halo could lead to positrons or antiprotons with distinctive energy signatures. With the High-Energy Antimatter Telescope (HEAT) balloon-borne instrument, we have measured the abundances of positrons and electrons at energies between 1 and 50 GeV. The data suggest that indeed a small additional antimatter component may be present that cannot be explained by a purely secondary production mechanism. Here we describe the signature of the effect and discuss its possible origin.     

Estimation of carbon stock for greenhouse gas emissions from hydropower reservoirs

The identification and accurate quantification of sources or sinks of greenhouse gas (GHG) have become a key challenge for scientists and policymakers working on climate change. The creation of a hydropower reservoir, while damming a river for power generation, converts the terrestrial ecosystems into aquatic and subsequently aerobic and anaerobic decomposition of flooded terrestrial soil organic matter resulting in the emission of significant quantity of GHG to the atmosphere. Tropical/subtropical hydropower reservoirs are more significant sources of GHG compared to boreal or temperate one. This paper aims to estimate the emission factor (gCO₂eq./kWh) and net GHG emission from Koteshwar hydropower reservoir in Uttarakhand, India. Further, estimated GHG are compared with those from global reservoirs located in the same eco-region so that its impact could be timely minimized/mitigated. Results have shown that emission factor and net GHG emission of Koteshwar reservoir are, respectively, estimated as 13.87 gCO₂eq./kWh and 167.70 Gg C year^?1 which are less than other global reservoirs located in the same eco-region. This information could be helpful for the hydropower industries to construct reservoirs in tropical eco-regions.     

Computation of ground motion amplification in Kolkata megacity (India) using finite-difference method for seismic microzonation

This paper presents the ground motion amplification scenario along with fundamental frequency (F ₀) of sedimentary deposit for the seismic microzonation of Kolkata City, situated on the world’s largest delta island with very soft soil deposit. A 4th order accurate SH-wave viscoelastic finite-difference algorithm is used for computation of response of 1D model for each borehole location. Different maps, such as for F ₀, amplification at F ₀, average spectral amplification (ASA) in the different frequency bandwidth of earthquake engineering interest are developed for a variety of end-users communities. The obtained ASA of the order of 3–6 at most of the borehole locations in a frequency range of 0.25–10.0 Hz reveals that Kolkata City may suffer severe damage even during a moderate earthquake. Further, unexpected severe damage to collapse of multi-storey buildings may occur in localities near Hoogly River and Salt Lake area due to double resonance effects during distant large earthquakes.     

GPR Signatures of Pipes and Walls with Emphasis on the Effect of Inclined Scanning Trajectory

This study investigates the effects of some commonly encountered constraints such as inclined scanning trajectory, multiple targets in the vicinity and material variation on GPR responses of pipes and walls. Further, the effects of wall inclination and broken walls are also explored in GPR signatures. Interpretation of such signatures in GPR data for archaeological and geotechnical surveys has been a challenge. A physical model was created to simulate buried pipes and walls under controlled conditions by maintaining density and moisture content of the soil medium. The presence of PVC pipes, plastered brick and stone walls buried in the dry sand have been investigated and major observations have been reported. The inclined scanning trajectory on buried pipes shows a change in curvature of hyperbola-like signatures. Inclined transects near the ends of pipes and walls manifest single limb GPR signatures. The responses of multiple pipes and walls show dependence on separation of targets and footprint of an antenna. One can discern stone walls from brick walls by recognizing the diffraction of waves by irregular stones in GPR responses. The signatures of walls differ from pipes with respect to the width of the apex and variation in the intensity in the limb.     

Deterministic seismic microzonation of Kolkata city

This paper presents the deterministic seismic microzonation of densely populated Kolkata city situated on the world’s largest delta island with very soft and thick soil deposit in the surficial layers. A fourth-order accurate staggered-grid finite-difference algorithm for SH-wave propagation simulation in visco-elastic medium is used for the linear computation of ground motion amplifications in sedimentary deposit. Different maps such as for fundamental frequency (F ₀), peak ground acceleration (PGA), peak ground velocity, and peak ground displacement are developed for variety of end-users communities, including structural and geotechnical engineers for performance-based designs, building officials, emergency managers, land-use planners, private businesses, and the general public. The scenario of simulated amplification factors in the different frequency bands revealed that the Kolkata city is very much prone to severe damage even during a moderate earthquake and very selective damage may occur at some of the localities during local and distant earthquakes. The deterministically predicted PGA at bedrock level is 0.0844 g and the maximum PGA predicted at the free surface is 0.6 g in Kolkata city due to maximum credible earthquake (M _w = 5.4) associated with Eocene Hinge Zone at a depth of 36 km. The seismic microzonation of Kolkata city reveals that the Nager Bazar and Nimtala areas are the safest regions with earthquake point of view.     

Photodegradation of amaranth in aqueous solution catalyzed by immobilized nanoparticles of titanium dioxide

The use of suspensions of nanoparticles of titanium dioxide in photocatalytic degradation of dye solution has disadvantages of inconvenient separation of fine particles for reuse and limited penetration of light for effective degradation. These problems can be minimized by supporting titanium dioxide on various inert supports. The present study involves the preparation of immobilized titanium dioxide films by three different techniques and characterization of the prepared films. The immobilized films of nanocrystals of titanium dioxide were prepared using sol?Cgel technique, polyvinyl alcohol?Cformaldehyde binder and acrylic emulsion. The photocatalytic performance of the prepared films for degradation of amaranth dye has also been evaluated and compared. Combination of photodegradation and adsorption processes induces strong beneficial effects on removal of dyes. Addition of high adsorption capacity activated carbon to photoactive titanium dioxide in photodegradation of dyes improves the efficiency of dye mineralization. The activated carbon has also been immobilized along with titanium dioxide in the present work to examine the dual effect of photodegradation and adsorption in the removal of amaranth. The films formed with the help of polyvinyl alcohol?Cformaldehyde binder showed better dye degradation capabilities.     

Evaluating the Long-term Urban Expansion of Ranchi Urban Agglomeration,India Using Geospatial Technology

The present study analyzes the built-up expansion of Ranchi urban agglomeration over a period of about 8 decades from 1927–2005. Satellite images and topographical maps were used to evaluate land use dynamics during these periods. Built-up growth of 473.7% during 1927–2005 was primarily at the expense of agricultural land along with reduction of natural water bodies reflects negative impacts of built-up expansion, which increased many folds in recent decades. The built-up growth is also analyzed with reference to population growth, land consumption rate and land transformation. The land loss due to increasing built-up growth of Ranchi were compared with other capital regions and cities along with population increase to provide insight into the possible scenario of built-up expansion in Ranchi urban area.     

Analysis of buried pipelines subjected to reverse fault motion

Presently available simplified analytical methods and semi-empirical methods for the analysis of buried pipelines subjected to fault motion are suitable only for the strike-slip and the normal-slip type fault motions, and cannot be used for the reverse fault crossing case. A simple finite element model, which uses beam elements for the pipeline and discrete nonlinear springs for the soil, has been proposed to analyse buried pipeline subjected to reverse fault motion. The material nonlinearities associated with pipe-material and soil, and geometric nonlinearity associated with large deformations were incorporated in the analysis. Complex reverse fault motion was simulated using suitable constraints between pipe-nodes and ground ends of the soil spring. Results of the parametric study suggest that the pipeline's capacity to accommodate reverse fault offset can be increased significantly by choosing a near-parallel orientation in plan with respect to the fault line. Further improvement in the response of the pipeline is possible by adopting loose backfill, smooth and hard surface coating, and shallow burial depth in the fault crossing region. For normal or near normal orientations, pipeline is expected to fail due to beam buckling at very small fault offsets.     

Sinkhole characterization in the Dead Sea area using airborne laser scanning

Since the early 1980s, the Dead Sea coast has undergone a near catastrophic land deterioration as a result of a rapid lake-level drop. One conspicuous expression of this deterioration is the formation of sinkholes fields that puncture the coastal plains. The evolution of sinkholes along nearly 70-km strip has brought to a halt the regional development in this well-known and toured area and destroyed existing infrastructures. Great efforts are being invested in understanding the phenomena and in development of monitoring techniques. We report in this paper the application of airborne laser scanning for characterization of sinkholes. We demonstrate first the appropriateness of laser scanning for this task and its ability to provide detailed 3D information on this phenomenon. We describe then an autonomous means for their extraction over large regions and with high level of accuracy. Extraction is followed by their detailed geometric characterization. Using this high-resolution data, we show how sinkholes of 0.5 m radius and 25 cm depth can be detected from airborne platforms as well as the geomorphic features surrounding them. These sinkhole measures account for their embryonic stage, allowing tracking them at an early phase of their creation.