The Impact of Radiation on the GABLS3 Large-Eddy Simulation through the Night and during the Morning Transition

Large-eddy simulation in the GABLS3 intercomparison is concerned with the developed stable boundary layer (SBL) and the ensuing morning transition. The impact of radiative transfer on simulations of this case is assessed. By the time of the reversal of the surface buoyancy flux, a modest reduction of the lapse rate in the developed SBL is apparent in simulations that include longwave radiation. Subsequently, with radiation, the developing mixed layer grows significantly more quickly, so that four hours after the transition the mixed layer is roughly 40 % deeper; the resulting profiles of potential temperature and specific humidity are in better agreement with observations. The inclusion of radiation does not substantively alter the shape of turbulent spectra, but it does indirectly reduce the variance of temperature fluctuations in the mixed layer. The deepening of the mixed layer is interpreted as a response to the reduction of the strength of the capping inversion, resulting from cumulative radiative cooling in the residual layer and around the top of the former SBL. Sensitivity studies are performed to separate the two effects. Solar radiative heating of the atmosphere has a smaller impact on the development of the mixed layer than does longwave radiative cooling and slightly reduces its rate of growth, compared to simulations including longwave radiation alone. These simulations demonstrate that nocturnal radiative processes have an important effect on the morning transition and that they should be considered in future large-eddy simulations of the transition.     

Basalt-rhyolite volcanism by MORB-continental crust interaction: Nd,Sr-isotopic and geochemical evidence from southern San Joaquin Basin,California

The early miocene Tecuya volcanic center in the southern San Joaquin basin of California consists of flows and tuffs of basalt and rhyolite that erupted, closely spaced in time, in both submarine and subaerial conditions. The rhyolites are overlain by the basalts and constitute approximately 45% of a total of at least 180 km³ of the Tecuya volcanic rocks. The basalts have _Nd(t) values of +2 to +6 and (⁸⁷Sr/⁸⁶Sr)_i values between 0.7035 and 0.7052. These rocks show LREE enrichment [(La/Yb)_N =2.4–5.5; La=28–150 times chondrite] and higher Th/U, Th/Ta, Rb/Ta, Ba/Ta, Cs/Rb but lower K/Rb ratios than MORB. Combined major- and trace-element, and Sr–Nd isotopic data suggest the involvement of subcontinental lithosphere, depleted upper mantle source (MORB), and local continental crust in the basalt petrogenesis. _Nd(t) values in rhyolites vary from +1.5 to +3.7 while (⁸⁷Sr/⁸⁶Sr)_i ratios range from 0.7051 to 0.7064. The rhyolites display LREE enrichment [(La/Yb)_N=10; La=100 times chondrite] along with a distinct negative Eu anomaly (Eu/Eu^*=0.75) and depletion of Ti and P. Mixing relations in (⁸⁷/⁸⁶Sr)_i – _Nd(t) space among basalts, rhyolites, and local continental crust indicate that the Tecuya rhyolites were produced by assimilation of variable amounts of continental crust by MORB-related magmas and subcontinental lithosphere-derived melts. This conclusion is supported by the synchroneity of Tecuya volcanism at 22 Ma with interaction of a segment of the East Pacific Rise along the southern California margin. The Tecuya volcanic rocks thus provide an example for the generation of rhyolitic melts owing to crustal assimilation by basaltic melts during mid-oceanic ridge-induced magmatism along a continental margin.     

Land,Labor, and Rural Development: Analyzing Participation in India's Village Dairy Cooperatives

Livestock-based livelihoods are currently being promoted by international development agencies as part of global efforts to combat poverty. India's dairy development program, organized around village cooperatives, has become an important model for such efforts. This article aims to identify household characteristics that influence membership in India's rural dairy cooperatives by comparing two villages representing different degrees of success. Utilizing logistic regression methods, data collected through a comprehensive survey of all households in the two villages are analyzed to examine (1) how variables describing animal ownership, agricultural attributes, and household labor availability contribute to explaining membership in the dairy cooperative; and (2) whether factors influencing membership differ across the two villages. Our results indicate that although agricultural property ownership influences cooperative membership in both villages, the kind of dairy animal used and labor utilized for dairying work also have a significant and context-specific effect on household participation.     

The chaotic time series of Indian monsoon rainfall and its prediction

The time series of Indian summer monsoon rainfall for the period 1871–1989 has been analysed using the method of deterministic chaos. It is found that a strange attractor underlies the time series implying the existence of a prediction function. This function has been approximated by a second-degree polynomial, involving the rainfalls of the past seven years and the coefficients have been estimated by least squares fit. The interannual variations of actual and computed rainfalls have been presented for a comparative study.     

A verification of spatio-temporal monsoon rainfall variability across Indian region using NWP model output

Evaluation of weather forecasting systems and assessment of existing verification procedures are essential to achieve desirable seamless rainfall prediction. Prediction of wet and dry spells is quite useful in agriculture and hydrology but very few attempts have been made so far to resolve the issue using numerical model output. Performance of five state-of-the-art global atmospheric general circulation models and their ensemble mean has been examined in predicting the parameters of wet and dry spells (WSs/DSs) during monsoon period of 2008–2011 over seven subzones of the Indian region. The number of WSs across the region is found to be underestimated, while total duration and rainfall amount of WSs (DSs) overestimated (underestimated). Start of the first WS is late and ends of the last WS early in the model forecast. More uncertainty is noticed in the prediction of DS rainfall and its duration than that of the WS. The percentage area of India under wet conditions (rainfall amount over each grid is more than its daily mean monsoon rainfall) and rainwater over the wet area is overestimated by about 59 and 32 %, respectively, in all models.     

Oxygen isotopes in coexisting garnets, clinopyroxenes and phlogopites of Roberts Victor eclogites: implications for petrogenesis and mantle metasomatism

δ¹⁸O values of coexisting garnet, clinopyroxene and phlogopite for twelve compositionally and texturally diverse Roberts Victor eclogite xenoliths range from +3.8 to +7.1, +4.0 to +7.4 and +5.9 to +7.4, respectively. Differences between theδ¹⁸O values of coexisting garnets and clinopyroxenes are normally zero; however, there is some variation in theδ¹⁸O values of different fractions of the same mineral in four samples which suggests the presence of isotopic zonation and inhomogeneity, possibly resulting from the introduction of a secondary fluid which metasomatized the eclogites and resulted in the formation of phlogopite, amphibole and celsian. Theδ¹⁸O value of the metasomatic fluid is generally buffered by the isotopic composition of the primary garnet and clinopyroxene, as indicated by a correlation between the isotopic composition of phlogopite and the primary pyroxene and garnet.The large range inδ¹⁸O values of the eclogites and the similarity in the isotopic composition of coexisting pyroxene and garnet support the interpretation that the Roberts Victor eclogites represent metamorphosed, altered basalts. The eclogites were subjected to infiltration metasomatism in the mantle prior to their incorporation in the kimberlite, and the source of this fluid was probably unrelated to the eclogite.     

The Schmidt hammer in rock material characterization

The Schmidt hammer provides a quick and inexpensive measure of surface hardness that is widely used for estimating the mechanical properties of rock material. However, a number of issues such as hammer type, normalization of rebound values, specimen dimensions, surface smoothness, weathering and moisture content, and testing, data reduction and analysis procedures continue to influence the consistency and reliability of the Schmidt hammer test results. This paper presents: a) a critical review of these basic issues; and b) the results of tests conducted on granitic rocks of various weathering grades in the light of the conclusions of this review. It was found that a very good correlation exists between L and N hammer rebound values and that both hammers are fairly sensitive to the physical properties, particularly to dry density though less so to effective and total porosities. The N hammer, producing a lesser scatter in the data, proved to be more efficient than the L hammer in predicting uniaxial compressive strength and Young's modulus. The exponential form of the correlation curves was found to reflect microstructural changes during the course of weathering and the differences in the probing scales or mechanisms in the means of measuring these mechanical properties, and could be generalized to other crystalline igneous rocks. The possibility of predicting weathering grades from rebound values was also explored. The changes in the rebound values during multiple impacts at a given point produced a better indication of the weathering grade than a single impact value. It was concluded that increasing the impact energy and plunger tip diameter should significantly reduce the scatter in coarse-grained weathered rocks and hence improve the reliability of the Schmidt hammer as a rock material characterization tool.     

Marine boundary layer simulation and verification during BOBMEX-Pilot using NCMRWF model

A global spectral model (T80L18) that is operational at NCMRWF is utilized to study the structure of the marine boundary layer over the Bay of Bengal during the BOBMEX-Pilot period. The vertical profiles of various meteorological parameters within the boundary layer are studied and verified against the available observations. The diurnal variation of various surface fields are also studied. The impact of non-local closure scheme for the boundary layer parameterisation is seen in simulation of the flow pattern as well as on the boundary layer structure over the oceanic region.     

SmNd study of Archean alkalic rocks from the Superior Province of the Canadian Shield

The Abitibi Volcanic Belt in eastern Superior Province of the Canadian Shield is the largest continuous greenstone belt in the world and is a key example of late Archean crust. This belt has, in general, suffered a low intensity of metamorphism and deformation, and, as a result, the stratigraphy and geology are well established. Tholeiitic and calc-alkaline series of igneous rocks are present in this belt in about equal proportions. However, the undersaturated potassic and leucitic volcanics of the Timiskaming Group are a unique feature of this belt.SmNd systematics were determined for twelve Timiskaming volcanic rocks. These rocks show nepheline, diopside and/or olivine plus leucite in the norm and a highly fractionated REE pattern. Sm and Nd concentrations range from 25 to 160 and 45 to 300 times the chondritic abundance, respectively. The Sm and Nd isotopic data yield an isochron age of 2702±105Ma for these volcanic rocks with an initial ε_Nd of +1.9±1.6. This age establishes the Timiskaming alkalic rock to be one of the oldest of their kind. From stratigraphic relations, 2705 Ma is an upper limit for the age and the ε_Nd values of +1.8 to +2.2 at this age for the twelve rocks are also upper limits. Further, this small but positive ε_Nd value for the isochron, when compared to other mantle-derived Archean rocks in the Superior Province, indicates that the Archean mantle was heterogeneous beneath the Canadian Shield and that the Timiskaming alkalic lavas were derived from a depleted mantle.