A Case Study of Turbulence in the Nocturnal Boundary Layer During the Indian Summer Monsoon

Observations from the Cloud-Aerosol Interaction and Precipitation Enhancement Experiment-Integrated Ground Observation Campaign (CAIPEEX-IGOC) provide a rare opportunity to investigate nocturnal atmospheric surface-layer processes and surface-layer turbulent characteristics associated with the low-level jet (LLJ). Here, an observational case study of the nocturnal boundary layer is presented during the peak monsoon season over Peninsular India using data collected over a single night representative of the synoptic conditions of the Indian summer monsoon. Datasets based on Doppler lidar and eddy-covariance are used for this purpose. The LLJ is found to generate nocturnal turbulence by introducing mechanical shear at higher levels within the boundary layer. Sporadic and intermittent turbulent events observed during this period are closely associated with large eddies at the scale of the height of the jet nose. Flux densities in the stable boundary layer are observed to become non-local under the influence of the LLJ. Different turbulence regimes are identified, along with transitions between turbulent periods and intermittency. Wavelet analysis is used to elucidate the presence of large-scale eddies and associated intermittency during nocturnal periods in the surface layer. Although the LLJ is a regional-scale phenomenon it has far reaching consequences with regard to surface-atmosphere exchange processes.     

Assessment of the impacts of climate change and brackish irrigation water on rice productivity and evaluation of adaptation measures in Ca Mau province,Vietnam

This paper presents applications of the peaks-over-threshold methodology for both the univariate and the recently introduced bivariate case, combined with a novel bootstrap approach. We compare the proposed bootstrap methods to the more traditional profile likelihood. We have investigated 63 years of the European Climate Assessment daily precipitation data for five Hungarian grid points, first separately for the summer and winter months, then aiming at the detection of possible changes by investigating 20 years moving windows. We show that significant changes can be observed both in the univariate and the bivariate cases, the most recent period being the most dangerous in several cases, as some return values have increased substantially. We illustrate these effects by bivariate coverage regions.     

Sulfur and carbon isotope compositions in the stratiform Zn-Pb-Cu sulfide deposits of the Rajpura-Dariba belt,Rajasthan, NW India: A model of ore genesis

The sulfur isotope composition of 86 sulfide minerals from the Middle Proterozoic, metamorphosed, stratiform, sediment-hosted Zn-Pb-CU sulfide deposits of Dariba and Sindeswar Kalan located within the Rajpura-Dariba belt in Rajasthan, NW India, have been determined. In addition, 16 carbonaceous and 2 carbonate rock samples from the ore zone have been analyzed for their C_tot and C_org contents and carbon isotope compositions. The sulfur isotope compositions range from 9.1 to –6.7 (mean value of 1.9). Increasing ³⁴S values stratigraphically upward are observed, particularly for pyrite and pyrrhotite suggesting a syngenetic origin for the sulfur. No marked lateral isotopic variations or isotopic variation in minerals from successive laminae in banded ore samples occur. Fractionation of sulfur isotopes between coexisting sulfides suggests that the original isotopic pattern was basically preserved during the amphibolite-facies metamorphism suffered by the deposits. C_org in carbonaceous rocks ranges 0.5–9.3 wt%, with ¹³C values between –21 and –31 (mean of –25.4) in keeping with the biogenic derivation of the carbon. Recrystallized dolostones have ¹³C values close to –14.4Geological evidence and isotopic features are consistant with the following genetic scheme: (a) base-metal ores along the belt formed from geothermal emanations carrying H₂S, produced by the chemical reduction of seawater sulfates and leaching of mafic volcanics, in a semiclosed (with respect to SO₄), shallow-water, rift-related basin with high biological activity; (b) pyrite and pyrrhotite formed diagenetically by bacterial reduction of sulfate in pore seawater in a system open to H₂S, thus bringing about the gradual enrichment of ³⁴S in these minerals stratigraphically upward; and (c) northward in the belt, at Sindeswar Kalan, the basin of ore deposition was relatively more open.     

Precambrian stromatolite and other structures in the Rajpura-Dariba polymetallic ore deposit,Rajasthan, India

Intimate association of 2 billion years old stromatolite with pyritic lead-zinc ores in the Precambrian polymetallic deposit at Rajpura-Dariba in Rajasthan, which hitherto remained unreported, provides an additional documentation of the syn(-dia)-genetic mineralization. The growth form and petrography of the stromatolite structure have been described and an explanation sought regarding the concentration of sulfides along the siliceous and carbonaceous laminations, as well as in the intercolumnar regions. Consideration of the geologic features noted in the mineralized zone and surrounding region suggests that the stratiform ores were deposited in a near-shore shallow marine environment, developed on basement highs and associated with euxinic conditions. Later, the ores were metamorphosed under conditions reaching upto amphibolite facies during a three-stage deformational history of their enclosing rocks. Some salient features of the secondary structures in the ores have been discussed in relation to this deformation history.     

Numerical Analysis of Sill and Crown Pillar Stability for Multilevel Cut and Fill Stopes in Different Geomining Conditions

A steeply dipping orebody, having decreasing width with depth has been modeled considering horizontal cut and fill method of stoping at four different depth levels. The focus of the study is to identify and understand the behavior of crown and sill pillars in terms of varying stress and geo-mining conditions without reinforcement using finite element method. Analysis of stresses, displacements and extent of yield zones around the excavation is carried out by varying the rock mass conditions such as geological strength index, uniaxial compressive strength (UCS or σ _ci), modulus of elasticity (E), and thickness of crown and sill pillars (T). These analyses have been conducted based on 135 non-linear numerical models considering Drucker–Prager material model in plane strain condition. Results of the study provide valuable insight into the stress concentration factors of the pillars highlighting stress distributions, roof convergence, yield zones and support requirements. Finally, it suggests the optimum thickness of crown and sill pillar with varying thickness of orebody.     

On convective entrainment in a mass flux cumulus parameterization

Summary A new entrainment/detrainment formulation in the Tiedtke’s mass flux cumulus parameterization is discussed here. Apart from validating it with observations both in one and three dimensional cases, it is also evaluated in the light of the results from the original Tiedtke scheme and another mass flux scheme due to Emanuel. The proposed analytical profiles of entrainment and detrainment, easier to implement in any mass flux scheme, give reasonable results in GCM experiments.     

Nonlinear analysis of multilayer extensible geosynthetic-reinforced granular bed on soft soil

The paper presents a model for the analysis of granular foundation beds reinforced with several geosynthetic layers. Such reinforced granular beds are often placed on soft soil strata for an efficient and economical transfer of superstructure load. The granular bed is modeled by the Pasternak shear layer and the geosynthetic reinforcement layers by stretched rough elastic membranes. The soft soil is represented by a series of nonlinear springs. The reinforcement has been considered to be extensible and it is assumed that the deformation at the interface of the reinforcements and soil are same. The nonlinear behavior of the granular bed and the soft soil is considered. Plane strain conditions are considered for the loading and reinforced foundation soil system. An iterative finite difference scheme is applied for obtaining the solution and results are presented in nondimensional form. The results from the proposed model are compared to the results obtained for multilayer inextensible geosynthetic reinforcement system. Significant reduction in the settlement has been observed when the number of reinforcement layer is increased. In case of inextensible reinforcements as the number of reinforcement layer is increased the settlement is decreased with a decreasing rate, but in case of extensible reinforcement the reduction rate is almost constant. Nonlinear behavior of the soft soil decreases as number of reinforcement layer is increased. The effect of the stiffness of the geosynthetic layer on the settlement response becomes insignificant for multilayer reinforced system, but the mobilized tension in the reinforcement layers increases as the stiffness of the geosynthetic layers increases.     

Numerical Analysis of Multi Layer Geosynthetic-Reinforced Granular Bed over Soft Fill

In this paper, considering the plain strain conditions, a numerical study has been conducted to investigate the behavior of multi layer geosynthetic-reinforced granular bed overlying a soft soil using the Fast Lagrangian Analysis of Continua (FLAC) program. The granular fill, soft soil, and geosynthetic reinforcements are considered as linear elastic materials. The geosynthetic reinforcements are modeled as cable elements fully bonded with the surrounding soil, thus neglecting any slip. The results obtained from the present investigation showed very close agreement when compared with the results of finite element analysis and lumped parameter modeling. The distribution of vertical, lateral and shear stresses in the soil are greatly affected as the number of reinforcement layers is increased. If the tensile stiffness of geosynthetic layers increases and its value is no more than 4,000–5,000 kN/m, the settlement of the reinforced foundation decreases significantly. The reduction in settlement is insignificant when the tensile strength of the geosynthetics exceed the above value.     

A nonlinear polar coordinate shallow water model for tsunami computation along North Sumatra and Penang Island

A nonlinear shallow water model in cylindrical polar coordinate system is developed, using an explicit finite difference scheme with a very fine resolution, to compute different aspects of tsunami at North Sumatra and the adjacent island Simeulue in Indonesia, and the Penang Island in Peninsular Malaysia. The pole of the frame is placed on the mainland of Penang (100.5°E) and the model area extends up to the west of Sumatra (87.5°E). The model is applied to simulate the propagation of tsunami wave towards North Sumatra, Simeulue and Penang Islands associated with Indonesian tsunami of 26 December 2004. The model is also applied to compute water levels along the coastal belts of those islands. Computed and observed water level data are found to be in good agreement and North Sumatra is found to be vulnerable for very high surges. The computed and observed arrival times of high surges are also in reasonable agreement everywhere. Further studies are carried out to investigate the effect of convective terms and it is found that their effects are insignificant in tsunami propagation and weakly significant for wave amplitude very near to the coast.     

The free nonlinear boundary value problem of physical geodesy

Summary Within potential theory of Poisson-Laplace equation the boundary value problem of physical geodesy is classified asfree andnonlinear. For solving this typical nonlinear boundary value problem four different types of nonlinear integral equations corresponding to singular density distributions within single and double layer are presented. The characteristic problem of free boundaries, theproblem of free surface integrals, is exactly solved bymetric continuation. Even in thelinear approximation of fundamental relations of physical geodesy the basic integral equations becomenonlinear because of the special features of free surface integrals.