A Wind Tunnel Model for Quantifying Fluxes in the Urban Boundary Layer

Transport of pollution and heatout of streets into the boundary layer above is not currently understood and so fluxes cannot be quantified. Scalar concentration within the street is determined by the flux out of it and so quantifying fluxes for turbulent flow over a rough urban surface is essential. We have developed a naphthalene sublimation technique to measure transfer from a two-dimensional street canyon in a wind tunnel for the case of flow perpendicular to the street. The street was coated with naphthalene, which sublimes at room temperature, so that the vapour represented the scalar source. The transfer velocity w_T relates the flux out of the canyon to the concentration within it and is shown to be linearly related to windspeed above the street. The dimensionless transfer coefficient w_T/U represents the ventilation efficiency of the canyon (here, w_T is a transfer velocity,U is the wind speed at the boundary-layer top). Observed values are between 1.5 and 2.7 ×10^-3 and, for the case where H/W0 (ratio of buildingheight to street width), values are in the same range as estimates of transfer from a flat plate, giving confidence that the technique yields accurate values for street canyon scalar transfer. w_T/U varies with aspect ratio (H/W), reaching a maximum in the wake interference regime (0.3 < H/W < 0.65). However, when upstream roughness is increased, the maximum in w_T/U reduces, suggesting that street ventilation is less sensitive to H/W when the flow is in equilibrium with the urban surface. The results suggest that using naphthalene sublimation with wind-tunnel models of urban surfaces can provide a direct measure of area-averaged scalar fluxes.     

Silicate and hydrocarbon emission from Galactic M supergiants

Following our discovery of unidentified infrared (UIR) band emission in a number of M supergiants in h and χ Per, we have obtained 10-μm spectra of a sample of 60 galactic M supergiants. Only three new sources, V1749 Cyg, UW Aql and IRC+40 427, appear to show the UIR bands; the others show the expected silicate emission or a featureless continuum. The occurrence of UIR-band emission in M supergiants is therefore much higher in the h and χ Per cluster than in the Galaxy as a whole. Possible explanations for the origin and distribution of UIR bands in oxygen-rich supergiants are discussed. We use our spectra to derive mass-loss rates ranging from 10⁻⁸ to 10⁻⁴ M_⊙ yr⁻¹ for the new sample, based on the power emitted in the silicate feature. The relationship between mass-loss rate and luminosity for M supergiants is discussed, and correlations are explored between their mid-infrared emission properties.     

Solar Photospheric and Chromospheric Observations using a Lithium Niobate Fabry-Perot Etalon

We have made a narrow band tunable filter for solar observations using a Lithium Niobate Fabry-Perot etalon. The 60 mm aperture etalon with a free spectral range of 4.22 Å and finesse of 26 at = 6122 Å has been procured from CSIRO, Australia. The wavelength tuning is achieved by applying high voltage to the etalon substrate at the rate of 0.45 Å per 1000 Volts. The filter is being used for imaging the sun in H line and obtaining Doppler- and Magnetogram in CaI 6122 Å line. In this paper, we present some initial observations carried out with this filter at Udaipur Solar Observatory.     

The Suburbanization of Food Insecurity: An Analysis of Projected Trends in the Atlanta Metropolitan Area

Although general patterns of food insecurity in the United States are known, few studies have attempted to estimate small area food security or account for ongoing socioeconomic changes. Here we address these issues by producing small area estimates of food insecurity in the Atlanta metropolitan area using two methodologies: fixed effects modeling and demographic metabolism. In both cases, we use county-level data from the Current Population Survey to determine the association between food insecurity and demographic predictors. These associations are then applied to tract-level data from the 2009 to 2013 American Community Survey and projected data for 2020 to create small area estimates of food insecurity. We find broad consensus between our two methods. For both time periods, food insecurity is highest in southern sections of the city of Atlanta and its neighboring suburbs. Projections to 2020, however, show that food insecurity rates are projected to increase in outer-ring suburbs east and west of the city while decreasing in the urban core. These results highlight the need to further adapt antihunger efforts for often sprawling suburban communities, where poverty rates are increasing but spatial mismatch combined with poor transit access might hinder access to food assistance.     

Hydrological modelling in the anthroposphere: predicting local runoff in a heavily modified high-alpine catchment

Hydrological models within inflow forecasting systems for high-alpine hydropower reservoirs can provide valuable information as part of a decision support system for the improvement of hydropower production or flood retention. The information, especially concerning runoff, is however rarely available for the calibration of the hydrological models used. Therefore, a method is presented to derive local runoff from secondary information for the calibration of the model parameters of the rainfallrunoff model COSERO. Changes in water levels in reservoirs, reservoir outflows, discharge measurements at water intakes and in transport lines are thereby used to derive the local, “natural” flow for a given sub-catchment. The proposed method is applied within a research study for the ÖBB Infrastructure Railsystem division in the Stubache catchment in the central Austrian Alps. Here, the ÖBB operates the hydropower scheme “Kraftwerksgruppe Stubachtal”, which consists of 7 reservoirs and 4 hydropower stations. The hydrological model has been set up considering this human influences and the high natural heterogeneity in topography and land cover, including glaciers. Overall, the hydrological model performs mostly well for the catchment with highest NSE values of 0.78 for the calibration and 0.79 for the validation period, also considering the use of homogeneous parameter fields and the uncertainty of the derived local discharge values. The derived runoff data proved to be useful information for the model calibration. Further analysis, examining the water balance and its components as well as snow cover, showed satisfactory simulation results. In conclusion, a unique runoff dataset for a small scale high-alpine catchment has been created to establish a hydrological flow prediction model which in a further step can be used for improved and sustainable hydropower management.     

Dynamics of settling-driven convection beneath a sediment-laden buoyant overflow: Implications for the length-scale of deposition in lakes and the coastal ocean

A series of laboratory experiments was conducted in order to determine how settling-driven convection influences the length-scale over which the majority of particles settle beneath a buoyant sediment-laden plume spreading over a denser saline layer. This system is analogous to sediment-laden river water spreading into a lake or the coastal ocean. The key dimensionless parameter that controls the settling dynamics of such flows is the density ratio, defined as the ratio of density differences due to the added salt and sediment. For a buoyant plume, this ratio has to be greater than unity, so that the experiments in the current study were performed for density ratios between one and five. When density ratio was close to one, settling-driven convection was vigorous and the length-scale over which sedimentation occurred was very small. A strong secondary turbidity current was generated in this case. On the other hand, for larger values of density ratio, the predicted length-scale over which a secondary plume was generated increased in proportion to the density ratio. A complete mathematical expression for this length-scale was developed using recent theory that described the timescale over which settling-driven convection evolved. The theoretically predicted propagation length-scale showed very good quantitative agreement with laboratory experiments. The use of the dimensionless density ratio allows the expression to predict which sediment-laden river plumes in lakes and the coastal ocean could quickly form secondary turbidity currents.     

Conceptualising and measuring psychological preparedness for disaster: The Psychological Preparedness for Disaster Threat Scale

Natural Hazards - Most research on household disaster preparedness has focussed on physical, or material, preparation. Recently, researchers have turned attention to investigating psychological, or...     

Observations on the effects of barite on the gill tissues of the suspension feeder Cerastoderma edule (Linné) and the deposit feeder Macoma balthica (Linné)

Barite, an important component of offshore drilling muds, is shown to adversely affect the ctenidia of the suspension feeding bivalve, Cerastoderma edule and the deposit feeder, Macoma balthica. SEM observations showed that exposure to barite caused cilia to shorten and coagulate, and, in some extreme cases, cause the disintegration of the gill structure itself. Using a simple ciliary condition index (CCI) the impact of the barite was quantified and damage rates expressed. The bivalves were treated with daily doses of 1, 2, and 3-mm depth equivalents of barite. In all treatments significant damage to the gills was recorded although, in the case of the 1-mm dose rate, this did not occur for 4 days. In the other two treatments, damage was apparent within a day of exposure with 100% mortality occurring within 12 days. Macoma balthica appeared slightly more tolerant of exposure to barite than C. edule.