The effects of urban heat islands (UHIs) have a substantial bearing on the sustainability of cities and environs. This paper examines the efficacy of green and cool roofs as potential UHI mitigation ...strategies to make cities more resilient against UHI. We have employed the urbanized version of the Weather Research and Forecasting (uWRF) model at high (1 km) resolution with physically-based rooftop parameterization schemes (conventional, green and cool), a first-time application to the Chicago metropolitan area. We simulated a hot summer period (16-18 August 2013) and assessed (i) UHI reductions for different urban landuse with green/cool roofs, (ii) the interaction of lake breeze and UHI, and (iii) diurnal boundary layer dynamics. The performance of uWRF was evaluated using sensible heat flux and air temperature measurements from an urban mini-field campaign. The simulated roof surface energy balance captured the energy distribution with respective rooftop algorithms. Results showed that daytime roof temperature reduced and varied linearly with increasing green roof fractions, from less than 1 °C for the case of 25% green roof to ∼3 °C during peak daytime for 100% green roof. Diurnal transitions from land to lake breeze and vice versa had a substantial impact on the daytime cycle of roof surface UHI, which had a 3-4 hour lag in comparison to 2 m UHI. Green and cool roofs reduced horizontal and vertical wind speeds and affected lower atmosphere dynamics, including reduced vertical mixing, lower boundary layer depth, and weaker convective rolls. The lowered wind speeds and vertical mixing during daytime led to stagnation of air near the surface, potentially causing air quality issues. The selection of green and cool roofs for UHI mitigation should therefore carefully consider the competing feedbacks. The new results for regional land-lake circulations and boundary layer dynamics from this study may be extended to other urbanized areas, particularly to coastal areas.
THE MATERHORN Fernando, H. J. S.; Pardyjak, E. R.; Di Sabatino, S. ...
Bulletin of the American Meteorological Society,
11/2015, Letnik:
96, Številka:
11
Journal Article
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Odprti dostop
Emerging application areas such as air pollution in megacities, wind energy, urban security, and operation of unmanned aerial vehicles have intensified scientific and societal interest in mountain ...meteorology. To address scientific needs and help improve the prediction of mountain weather, the U.S. Department of Defense has funded a research effort—the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program—that draws the expertise of a multidisciplinary, multiinstitutional, and multinational group of researchers. The program has four principal thrusts, encompassing modeling, experimental, technology, and parameterization components, directed at diagnosing model deficiencies and critical knowledge gaps, conducting experimental studies, and developing tools for model improvements. The access to the Granite Mountain Atmospheric Sciences Testbed of the U.S. Army Dugway Proving Ground, as well as to a suite of conventional and novel high-end airborne and surface measurement platforms, has provided an unprecedented opportunity to investigate phenomena of time scales from a few seconds to a few days, covering spatial extents of tens of kilometers down to millimeters. This article provides an overview of the MATERHORN and a glimpse at its initial findings. Orographic forcing creates a multitude of time-dependent submesoscale phenomena that contribute to the variability of mountain weather at mesoscale. The nexus of predictions by mesoscale model ensembles and observations are described, identifying opportunities for further improvements in mountain weather forecasting.
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Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Growth in adoption of distributed wind turbines for energy generation is significantly impacted by challenges associated with siting and accurate estimation of the wind resource. Small turbines, at ...hub heights of 40 m or less, are greatly impacted by terrestrial obstacles such as built structures and vegetation that can cause complex wake effects. While some progress in high-fidelity complex fluid dynamics (CFD) models has increased the potential accuracy for modelling the impacts of obstacles on turbulent wind flow, these models are too computationally expensive for practical siting and resource assessment applications. To understand the efficacy of available models in situ, this study evaluates classic and commonly used methods alongside new state-of-the-art lower-order models derived from CFD simulations and machine learning approaches. This evaluation is conducted using a subset of an extensive original dataset of measurements from more than 300 operational wind turbines in the northern Netherlands. The results show that data-driven methods (e.g. machine learning and statistical modelling) are most effective at predicting production at real sites with an average error in annual energy production of 2.5 %. When sufficient data may not be available de novo to support these data-driven approaches, models derived from high-fidelity simulations show promise and reliably outperform classic methods. On average these models have 6.3 %–11.5 % error compared with 26 % for classic methods and 27 % baseline error for reanalysis data without obstacle correction. While more performant on average, these methods are also sensitive to the quality of obstacle descriptions and reanalysis inputs.
The 'reared apart' model, eliminating the effect of common environmental factors, is used extensively in twins research. In this study, teeth present (TP), teeth present excluding third molars ...(TPX3), teeth restored (TR), teeth restored index (TRI), surfaces restored (SR), surfaces restored index (SRI) and surfaces restored or carious (SRCI), were compared in 46 monozygotic (MZ) twin pairs and 22 dizygotic (DZ) twin pairs separated during infancy and raised apart. The dental examination included charting, panoral and bitewing radiographs, study models and a questionnaire. Data were analysed using intraclass correlations (ICC) and analysis of variance (corrected for age and sex). For all characteristics, the MZ pairs showed greater within-pair similarity than DZ pairs. For MZ pairs, the ICC values for the dental characteristics were all statistically significant (p < 0.005): TP, 0.45; TPX3, 0.49; TR, 0.57; TRI, 0.61; SR, 0.46; SRI, 0.67; SRCI, 0.58. For DZ pairs, none of the ICC values reached statistical significance: TP, 0.04; TPX3, 0.11; TR, 0.30; TRI, 0.31; SR, 0.20; SRI, 0.17; SRCI, 0.26. Despite subjects being reared in different environments, receiving different diets and different dental professional care, the MZ findings demonstrated significant genetic variance (45-67%) for the number of teeth present, number of teeth and surfaces restored, and caries present; the DZ data supported this conclusion. These findings provide new evidence for a genetic contribution to dental caries.
The purpose of this study was to estimate the genetic variance for alveolar bone height by means of the classic twin method and the study of monozygous twins reared apart. Panoramic radiographs were ...obtained from 120 pairs of adult twins (mean age = 40.4 years, S.D. = 10.4 years), for comparison of 62 pairs of monozygous twins reared together (MZT), 25 pairs of like-sexed dizygous twins reared together (DZT), and 33 pairs of monozygous twins reared apart (MZA). Mesial and distal bone heights were determined as a proportion of tooth length. A full-mouth bone score was computed for each twin by averaging these proportions from all measurable teeth. Between-pair (B) and within-pair (W) variances were computed for each twin group. The population variances (B + W) of the MZT and DZT twin groups were similar, which validated a basic assumption of the twin model. Intraclass correlations and heritability estimates were also computed for the reared-together and reared-apart twin groups. Boot-strap sampling was used to provide estimates and confidence limits for these values. The intraclass correlations for the twin groups were: MZT = 0.70, DZT = 0.52, and MZA = 0.55. The results of this study suggest that there is significant genetic variance in the population for proportional alveolar bone height.
After the accidental introduction of the Brown Tree Snake, Boiga irregularis , to the island of Guam after World War II, the snake became exceedingly numerous, and most of Guam's native vertebrates ...either became endangered or disappeared from the island. In this paper we summarize what is known about populations of this snake on Guam and the likely origin of the Guam population. Scale counts and transportation records suggest that the Guam population originated in the Admiralty Islands, about 1500 km south of Guam. It was probably transported to Guam in ships that transported salvaged war material after World War II. For ca. 35 yr after its introduction, the presence of the snake on Guam was documented only by popular accounts, occasional photographs, and a few museum specimens, indicating that the snake's distribution was fairly limited initially, but ultimately a period of sharp population growth and wide dispersal occurred, with the snake reaching all parts of the island by the late 1960s. Peak population levels were attained about a decade or more after each area was colonized. Mar-recapture and removal data indicate that the capture of 50 snakes per ha at one site in northern Guam during 1985 probably represented a population density of around 100 snakes per ha, but by 1988 this population had declined to around 30% of the 1985 density. However, this reduction may not be permanent. In central Guam, where the snake irrupted decades ago, the snake's numbers have continued to fluctuate, and in some cases it has attained densities in excess of 50 per hectare.
Laser beams are wave-like optical disturbances. They are characterized by a dominant direction of propagation and a finite extent transverse to the direction of propagation. Many characteristics of ...laser beams can be described in terms of a scalar function multiplied by a constant vector, which can be real (for linear polarization) or complex (for elliptical polarization). The scalar function is a solution to the paraxial scalar wave equation. This scalar description, however, fails to describe the polarization and focusing characteristics of laser beams correctly. For a correct accounting of these characteristics, the electric and magnetic fields associated with laser beams must satisfy not only the wave equation but also the Maxwell's equations. We show that, due to the finite transverse size of laser beams, Maxwell's equations require that the electric field (as well as the magnetic field) associated with laser beams will possess all three nonzero Cartesian components even in free space. Each component can be expressed in terms of the scalar solutions of the paraxial wave equation. We construct three-component solutions giving expressions for the dominant, cross, and longitudinal-polarization components, for linearly polarized Hermite-Gauss and Laguerre-Gauss beams. Such a description correctly accounts for focusing as well as polarization properties of laser beams. We demonstrate the validity of this description experimentally by generating two families of laser beams and verify the existence of cross-polarization field components and their evolution in propagation. We generate experimental higher-order Hermite-Gauss laser beams intracavity via a pair of crossed fibers. Laguerre-Gauss laser beams were generated by converting Hermite-Gauss beams into Laguerre-Gauss beams of the same order by using a pair of cylindrical lenses to manipulate Guoy phase of the beams. Intensity profiles of the dominant and cross-polarization components of linearly polarized Hermite-Gauss and Laguerre-Gauss beams are measured and their evolution as the beam propagates away from its focal region was studied. The transverse profiles of the cross-polarization components of these beams undergo an evolution with propagation. The theoretically expected and experimentally observed intensity profiles are in reasonable agreement confirming the field structure of laser beams derived in this thesis.
SUPPLEMENT Fernando, H. J. S.; Pardyjak, E. R.; Di Sabatino, S. ...
Bulletin of the American Meteorological Society,
11/2015, Letnik:
96, Številka:
11
Journal Article
Recenzirano
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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