Performance of vegetated roofs are investigated in terms of their expected benefits for the building and the urban environment, due to their recognised energy and water management potential scores. A ...review of related worldwide experiences is reported for comparison purposes. The investigation is here performed within the specific climatic context of the Mediterranean region. Full-scale experimental results are provided from two case studies, located in north-west and central Italy, consisting in two fully monitored green roofs on top of public buildings. The attenuation of solar radiation through the vegetation layer is evaluated as well as the thermal insulation performance of the green roof structure. The daily heat flow through the roof surface is quantified showing that the green roof outperforms the reference roof, therefore reducing the daily energy demand. As for water management, it is confirmed that green roofs significantly mitigate storm water runoff generation – even in a Mediterranean climate – in terms of runoff volume reduction, peak attenuation and increase of concentration time, although reduced performance could be observed during high precipitation periods.
► Non-dimensional analysis allows optimum sizing of rainwater harvesting systems. ► The demand fraction is the main parameter controlling the system behavior. ► The storage fraction controls the ...detention time (water quality degradation). ► 30
years of daily rainfall data are sufficient to assess the system performance. ► Different precipitation regimes scarcely impact an optimum tank sizing.
The use of non-dimensional parameters is proposed in this study to investigate optimum performance of rainwater harvesting systems. A suitable behavioral model is implemented to assess the inflow, outflow and change in storage volume of a rainwater harvesting system according to a daily mass balance equation under historical precipitation observations. The model determines the water-saving efficiency, overflow ratio and detention time. These are interpreted as a measure of the system performance over the long-term simulation period. Performance is examined under various scenarios in terms of environmental conditions that are typical of the Italian territory (3 precipitation regimes and 3 levels of water demand) and system characteristics (10 storage capacity levels). Optimum sizing of the rainwater harvesting system is investigated as a function of two non-dimensional parameters: the demand fraction and the storage fraction. The demand fraction is shown to affect significantly the water-saving efficiency and overflow ratio, while the storage fraction controls the detention time thus influencing the water quality degradation within the system. Sensitivity analysis is carried out to investigate the influence of the length of the time series climate records on the reliability of the selected performance indices. Results demonstrate that 30 years of daily rainfall records are sufficient to allow suitable assessment of the system performance. Optimum system design based on the medium demand fraction and the low storage fraction determines system performance that appears almost independent on the three precipitation regimes investigated.
The wind‐induced bias of catching‐type precipitation measurement instruments is quantified using Computational Fluid Dynamics with embedded liquid (raindrops) and solid (snowflakes) particle ...tracking. The performance of six common commercial gauges having different outer geometry is compared under a range of Precipitation Intensity (PI) and wind speed conditions by means of the numerically calculated catch ratios. Validation of the simulated aerodynamic behavior and its effect on water drop trajectories is provided by previous wind tunnel experiments. The functional dependence of the overall collection efficiency on the PI is derived as a quantitative measure of the instrument performance under a wind climatology with a uniform probability density function. Instruments with aerodynamic design produce a less pronounced diversion of hydrometeor trajectories—at any given size—than those having more traditional geometry. For liquid precipitation measurements, chimney‐shaped instruments rank low, while inverted conical and Nipher shielded instruments are quite performant solutions. The investigated quasi‐cylindrical gauges have intermediate behavior depending on their detailed aerodynamic features. For solid precipitation, all instruments rank low at light to moderate PI, except the Nipher shielded gauge. Results allow selecting the appropriate instrument for the local precipitation climatology at the measurement site and can be used to apply suitable adjustments to the measured precipitation.
Key Points
The wind induced bias of six common precipitation gauges is quantified using Computational Fluid Dynamics with embedded particle tracking
Overall collection efficiency trends with precipitation intensity show that the gauge performance varies according to its outer geometry
Results allow selecting appropriate gauge models for the local precipitation climatology and applying adjustments to the measured data
The analysis of the interactions between hydrologic processes and green roof installations in the urban environment requires to improve the understanding of the unsaturated water flow in the ...coarse-grained porous media usually employed in such technological solutions. In order to base our research on experimental evidences, a monitoring program was carried out at the green roof experimental site of the University of Genoa (Italy). A continuous acquisition system is available at the experimental site for rainfall intensity and subsurface water flow measurements at 1
min resolution. Soil water content is also measured at the same resolution in time by four TDR probes located along a vertical profile. The SWMS_2D model, based on Richards’ law and the Van Genuchten–Mualem functions, is here applied to simulate the variably saturated flow within the green roof system. The model was calibrated and validated using rainfall–runoff events observed at the experimental site. The calibration and validation strategy involved comparing predicted and measured outflow hydrographs. The model adequately reproduces the hydrographs, as demonstrated by the limited relative percentage deviations obtained for the total discharged volume, the peak flow and the hydrograph centroid. Furthermore the predicted water content closely matches the observed one at various depths along the vertical profile where measurements are available, thus confirming that the model correctly describes the variably saturated flow field within the green roof. The mechanistic model, based on a single porosity approach, here employed to describe the variably saturated flow within the thin stratigraphy, is demonstrated to suitably describe the hydrologic performance of a green roof, which is typically realized with high hydraulic conductivity and coarse-grained porous media.
Abstract Dry eye is a common, multifactorial disease currently diagnosed by a combination of symptoms and signs. However, the subjective symptoms of dry eye poorly correlate to the current gold ...standard for diagnostic tests, reflecting the need to develop better objective tests for the diagnosis of dry eye. This review considers the role of ocular surface matrix metalloproteinase 9 (MMP-9) in dry eye and the implications of a novel point-of-care test that measures MMP-9 levels, InflammaDry (RPS, Sarasota, FL) on choosing appropriate therapeutic treatments.
Despite the apparent simplicity, it is notoriously difficult to measure rainfall accurately because of the challenging environment within which it is measured. Systematic bias caused by wind is ...inherent in rainfall measurement and introduces an inconvenient unknown into hydrological science that is generally ignored. This paper examines the role of rain gauge shape and mounting height on catch efficiency (CE), where CE is defined as the ratio between nonreference and reference rainfall measurements. Using a pit gauge as a reference, we have demonstrated that rainfall measurements from an exposed upland site, recorded by an adjacent conventional cylinder rain gauge mounted at 0.5 m, were underestimated by more than 23% on average. At an exposed lowland site, with lower wind speeds on average, the equivalent mean undercatch was 9.4% for an equivalent gauge pairing. An improved‐aerodynamic gauge shape enhanced CE when compared to a conventional cylinder gauge shape. For an improved‐aerodynamic gauge mounted at 0.5 m above the ground, the mean undercatch was 11.2% at the upland site and 3.4% at the lowland site. The mounting height of a rain gauge above the ground also affected CE due to the vertical wind gradient near to the ground. Identical rain gauges mounted at 0.5 and 1.5 m were compared at an upland site, resulting in a mean undercatch of 11.2% and 17.5%, respectively. By selecting three large rainfall events and splitting them into shorter‐duration intervals, a relationship explaining 81% of the variance was established between CE and wind speed.
Plain Language Summary
This study was motivated by how challenging it is to measure rainfall accurately, despite it appearing to be very simple. Rainfall measurement is important to society because it has so many everyday uses, such as food production and weather forecasting, and applications that are critical to life, such as flood warning and effective management of water resources. Rainfall is difficult to measure because it varies so much in time and space, and the measurement of rain is highly affected by how windy it is, which also varies in time and space. Therefore, when it rains at the same time as being very windy, which is common during many storms, rainfall measurements are greatly underestimated. The uplands generally receive more rainfall and higher wind speeds than the lowlands, therefore it follows that we underestimate rainfall by more in the uplands. This is important because rainfall measurements in the uplands are sparse, yet it is in such areas where many floods originate. This study shows that the underestimation of rainfall at a site in the windy Scottish uplands was more than 23% on average. It then suggests some techniques that can be implemented to improve the measurement of rainfall.
Key Points
Rainfall in windy upland areas can be greatly underestimated due to wind‐induced undercatch
The mounting height and shape of a rain gauge is more important for accurate rainfall measurement than is widely appreciated
An improved‐aerodynamic rain gauge shape is the simplest and cheapest method of enhancing rainfall catch
In situ detection of boron by ChemCam on Mars Gasda, Patrick J.; Haldeman, Ethan B.; Wiens, Roger C. ...
Geophysical research letters,
16 September 2017, Volume:
44, Issue:
17
Journal Article
Peer reviewed
Open access
We report the first in situ detection of boron on Mars. Boron has been detected in Gale crater at levels <0.05 wt % B by the NASA Curiosity rover ChemCam instrument in calcium‐sulfate‐filled ...fractures, which formed in a late‐stage groundwater circulating mainly in phyllosilicate‐rich bedrock interpreted as lacustrine in origin. We consider two main groundwater‐driven hypotheses to explain the presence of boron in the veins: leaching of borates out of bedrock or the redistribution of borate by dissolution of borate‐bearing evaporite deposits. Our results suggest that an evaporation mechanism is most likely, implying that Gale groundwaters were mildly alkaline. On Earth, boron may be a necessary component for the origin of life; on Mars, its presence suggests that subsurface groundwater conditions could have supported prebiotic chemical reactions if organics were also present and provides additional support for the past habitability of Gale crater.
Key Points
First detection of boron on Mars' surface
Presence of boron in Gale crater suggests evaporite deposits may be present stratigraphically above the detected boron
Borates can stabilize ribose in aqueous solutions and thus may be important for prebiotic chemistry
Pluvial flooding in urban areas may derive from the limited or temporarily reduced efficiency of surface drainage, even when the underlying storm sewers are properly designed. This study focuses on ...the impact of uncertainties in the operational condition of the surface drainage system on pluvial flood hazard. The flood propagation model FLURB‐2D is implemented on a selected study area in the town of Genoa (Italy). Synthetic hyetographs based on the Chicago and bivariate copula methods with suitable return periods are used as input. While simulating the design rainfall, inlet operational conditions are varied stochastically using a Monte Carlo approach. Results confirm that microtopography has the potential to impact the efficiency of surface drainage and consequently to produce local flooding, with significant water depth in zones of flow concentration. Furthermore, the derived inundation maps allow the highlighting of areas with insufficient design of the surface drainage system (inlet size and positioning).
A physical full‐scale experimental set‐up was designed and implemented in the wind tunnel to reproduce and capture the trajectories of falling water drops when approaching the collector of catching ...type precipitation gauges, reproducing rainfall measurements in windy conditions. The experiment allowed to collect, for the first time, a large data set of high‐resolution footages of the deviation of such trajectories, as induced by the bluff‐body aerodynamics of the outer gauge shape. By processing the collected images, a consistent quantitative interpretation of each drop pattern was possible, based on a detailed Computational Fluid Dynamics simulation of the airflow updraft and acceleration features above the collector of the gauge. Numerical airflow simulations were extensively validated in the wind tunnel, using local flow measurements and Particle Image Velocimetry. Capturing the deviation of the drop trajectories in the wind tunnel allowed a clear visualization of the physical reason for the wind‐induced undercatch of precipitation gauges, since drops were individually observed to fall outside instead of inside of the collector, contrary to what would be expected by extrapolating their undisturbed trajectory. The adopted Lagrangian Particle Tracking model and the formulation used for the drag coefficient were suitable to closely reproduce the observed drop trajectories when affected by the airflow deformation due to the bluff‐body aerodynamics of two investigated gauge geometries. The wind tunnel experiment provided the basis for the validation of the particle tracking model in terms of the difference between simulated and observed trajectories, after initial conditions were suitably set to represent the experimental setup.
Key Points
Water drops are released in a wind tunnel to mimic rainfall and tracked to observe the wind‐induced measurement bias of raingauges
Numerical simulation of the airflow field and a lagrangian particle tracking model are applied to reproduce the drop trajectories
Wind tunnel tests validate airflow simulation and particle tracking results supporting their application in studying the wind‐induced bias
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