Ensemble Kalman filter versus ensemble smoother for assessing hydraulic conductivity via tracer test data assimilation

Abstract. Estimating the spatial variability of hydraulic conductivity K in natural aquifers is important for predicting the transport of dissolved compounds. Especially in the nonreactive case, the plume evolution is mainly controlled by the heterogeneity of K. At the local scale, the spatial distribution of K can be inferred by combining the Lagrangian formulation of the transport with a Kalman-filter-based technique and assimilating a sequence of time-lapse concentration C measurements, which, for example, can be evaluated on site through the application of a geophysical method. The objective of this work is to compare the ensemble Kalman filter (EnKF) and the ensemble smoother (ES) capabilities to retrieve the hydraulic conductivity spatial distribution in a groundwater flow and transport modeling framework. The application refers to a two-dimensional synthetic aquifer in which a tracer test is simulated. Moreover, since Kalman-filter-based methods are optimal only if each of the involved variables fit to a Gaussian probability density function (pdf) and since this condition may not be met by some of the flow and transport state variables, issues related to the non-Gaussianity of the variables are analyzed and different transformation of the pdfs are considered in order to evaluate their influence on the performance of the methods. The results show that the EnKF reproduces with good accuracy the hydraulic conductivity field, outperforming the ES regardless of the pdf of the concentrations

Effects of temperature on flood forecasting: analysis of an operative case study in Alpine basins

Abstract. In recent years the interest in the forecast and prevention of natural hazards related to hydro-meteorological events has increased the challenge for numerical weather modelling, in particular for limited area models, to improve the quantitative precipitation forecasts (QPF) for hydrological purposes. After the encouraging results obtained in the MAP D-PHASE Project, we decided to devote further analyses to show recent improvements in the operational use of hydro-meteorological chains, and above all to better investigate the key role played by temperature during snowy precipitation. In this study we present a reanalysis simulation of one meteorological event, which occurred in November 2008 in the Piedmont Region. The attention is focused on the key role of air temperature, which is a crucial feature in determining the partitioning of precipitation in solid and liquid phase, influencing the quantitative discharge forecast (QDF) into the Alpine region. This is linked to the basin ipsographic curve and therefore by the total contributing area related to the snow line of the event. In order to assess hydrological predictions affected by meteorological forcing, a sensitivity analysis of the model output was carried out to evaluate different simulation scenarios, considering the forecast effects which can radically modify the discharge forecast. Results show how in real-time systems hydrological forecasters have to consider also the temperature uncertainty in forecasts in order to better understand the snow dynamics and its effect on runoff during a meteorological warning with a crucial snow line over the basin. The hydrological ensemble forecasts are based on the 16 members of the meteorological ensemble system COSMO-LEPS (developed by ARPA-SIMC) based on the non-hydrostatic model COSMO, while the hydrological model used to generate the runoff simulations is the rainfall–runoff distributed FEST-WB model, developed at Politecnico di Milano

Torino: A Tangible Programming Language Inclusive of Children with Visual Disabilities

© 2018, Copyright © 2018 Taylor & Francis Group, LLC. Across the world, policy initiatives are being developed to engage children with computer programming and computational thinking. Diversity and inclusion has been a strong force in this agenda, but children with disabilities have largely been omitted from the conversation. Currently, there are no age appropriate tools for teaching programming concepts and computational thinking to primary school children with visual disabilities. We address this gap through presenting the design and implementation of Torino, a tangible programming language for teaching programming concepts to children age 7–11 regardless of level of vision. In this paper, we: (1) describe the design process done in conjunction with children with visual disabilities; (2) articulate the design decisions made; and (3) report insights generated from an evaluation with 10 children with mixed visual abilities that considers how children are able to trace (read) and create (write) programs with Torino. We discuss key design trade-offs: (1) readability versus extensibility; and (2) size versus liveness. We conclude by reflecting upon how an inclusive design approach shaped the final result

Hydraulic conductivity estimate via tracer test and ensemble Kalman filter data assimilation: theoretical and numerical fundamentals

Hydraulic properties of natural aquifers, such as porosity, hydraulic conductivity, and storativity, exhibit an erratic spatial variability at different scales that is difficult to recognize without expensive in situ sampling campaigns, laboratory analyses, and, when available, spatially distributed pumping tests. Nevertheless, the importance of the heterogeneous structure of natural formations on solute transport is well recognized, being the non-Fickian evolution of contaminant plumes and the relevant dispersive phenomena controlled by the variability of the hydraulic conductivity K at the local scale. Tracer test analyses have been widely adopted to identify the complex distribution of in situ hydraulic properties. In particular, the use of geophysical methods like the borehole Electrical Resistivity Tomography (ERT) have been in rapid increase, due to their potential to accurately describe the spatio-temporal evolution of the injected solute. Under the assumptions that the solute spreads as a passive tracer and with high values of the Peclet number, the plume evolution is controlled by the porosity and the spatial distribution of hydraulic conductivity. Combining the Lagrangian formulation of transport and the ensemble Kalman filter (EnKF) data assimilation technique, the purpose of this study is to infer the spatial distribution of K at the local scale from a sequence of time-lapse concentration imaging. The capabilities of the proposed approach are investigated simulating various assimilation experiments via synthetic tracer tests in a three-dimensional finite domain reproducing a heterogeneous aquifer. In a first scenario, all the available concentration measurements are assimilated and the entire hydraulic conductivity field is updated, while in the remaining scenarios the K values are updated only in a limited number of nodes by assimilating the concentrations in these same nodes, the hydraulic conductivity in the rest of the domain being the result of a subsequent conditional generation. The performance of the method is carefully analyzed in terms of root mean square error of the reconstructed hydraulic log-conductivity field. Besides to highlight its weakness and strength, the results show that the proposed approach can represent an effective tool for describing the hydraulic conductivity distribution at the locale scale

Helping the surgeon: epicardial 3D echocardiography in aortic dissection

A74-year-old woman was admitted to the emergency room with acute severe chest pain, dyspnoea and a history of giant cell arteritis and polymyalgia rheumatica. Her heart rate was 95 beats/min, arterial blood pressure was 100/60 mm Hg, and a diastolic murmur was present along the right upper sternal border. She was neurologically intact, with clear lungs, palpable normal pulses in the right radial and in both femoral arteries, and a filiform left radial pulse. Transthoracic echocardiography revealed aortic dissection type A with moderate aortic regurgitation. Aortography confirmed the diagnosis and the extension of the dissection. The patient was taken into the operating room where, after sternotomy, real-time threedimensional (RT3DE) epicardial echocardiography was carried out (iE33, Philips) with the new probe X5-1, demonstrating the tear (panel A). The exact location and dimension of the tear were easily pointed out, 5 mm from the sinotubular junction, with the false lumen reaching the aortic root above the coronary ostia (panel B). The patient underwent aortic dissection repair with a ‘‘button Bentall’’ procedure with a biologic prosthesis. RT3DE offered to the surgeon an impressive, dynamic, precise assessment of the tear and a realistic representation of the anatomical dissection, which was useful for surgical planning