European precipitation connections with large-scale mean sea-level pressure (MSLP) fields

To advance understanding of hydroclimatological processes, this paper links spatiotemporal variability in gridded European precipitation and large-scale mean sea-level pressure (MSLP) time series (1957–2002) using monthly concurrent correlation. Strong negative (positive) correlation near Iceland and (the Azores) is apparent for precipitation in northwest Europe, confirming a positive North Atlantic Oscillation (NAO) association. An opposing pattern is found for southwest Europe, and the Mediterranean in winter. In the lee of mountains, MSLP correlation is lower reflecting reduced influence of westerlies on precipitation generation. Importantly, European precipitation is shown to be controlled by physically interpretable climate patterns that change in extent and position from month to month. In spring, MSLP–precipitation correlation patterns move and shrink, reaching a minimum in summer, before expanding in the autumn, and forming an NAO-like dipole in winter. These space–time shifts in correlation regions explain why fixed-point NAO indices have limited ability to resolve precipitation for some European locations and seasons

Optimal Data Split Methodology for Model Validation

The decision to incorporate cross-validation into validation processes of mathematical models raises an immediate question - how should one partition the data into calibration and validation sets? We answer this question systematically: we present an algorithm to find the optimal partition of the data subject to certain constraints. While doing this, we address two critical issues: 1) that the model be evaluated with respect to predictions of a given quantity of interest and its ability to reproduce the data, and 2) that the model be highly challenged by the validation set, assuming it is properly informed by the calibration set. This framework also relies on the interaction between the experimentalist and/or modeler, who understand the physical system and the limitations of the model; the decision-maker, who understands and can quantify the cost of model failure; and the computational scientists, who strive to determine if the model satisfies both the modeler's and decision maker's requirements. We also note that our framework is quite general, and may be applied to a wide range of problems. Here, we illustrate it through a specific example involving a data reduction model for an ICCD camera from a shock-tube experiment located at the NASA Ames Research Center (ARC).Comment: Submitted to International Conference on Modeling, Simulation and Control 2011 (ICMSC'11), San Francisco, USA, 19-21 October, 201

Integrated geophysical methods to characterize subsidence in Butte, Montana, U.S.A.

Geophysical investigations, designed to characterize unique subsidence features of unknown natural origin, provide imaging analysis of potential causes of subsidence. Recent subsidence in the alluvial plain in Butte, Montana is unrelated to historic mining in the area. This study aims to utilize a combined application of shallow electrical resistivity tomography (ERT), self-potential (SP), and frequency-domain electromagnetic (FDEM) methods in order to develop a better understanding of the particular set of hydrogeological and environmental conditions that contribute to this unique phenomena. Geophysical measurements provide lateral and vertical variations of electrical resistivity in the subsurface to a depth of 10 m while also contouring the streaming potential in each site to help characterize the site-specific groundwater flow components. Least-square inversion resistivity models and conductivity from electromagnetic data are compared to known well lithologic information to identify general variations of sediments with depth as well as delineate the extent of the known subsidence features. Site investigations indicate that the subsidence features in basin fill sediments are spatially associated with electrical and electromagnetic signatures of water seepage and sharp contacts between resistive and conductive sediment layers. ERT results showed a circular resistive anomaly in place of known subsidence locations and delineated lithologic heterogeneity in each site, suggesting a clay contact at shallow depth. The FDEM results complemented ERT and further characterized the depth and thickness of the clay lens. The SP results indicated surficial seepage associated with subsidence locations. This work sets a baseline site characterization and analysis on the origin of these subsidence features, where the subsidence is expected to be associated with volumetric changes in clay and porous media during surficial seepage

Probabilistic estimates of climate change impacts on UK water resources

Climate change will increase temperatures and change rainfall across the UK. In turn, this will modify patterns of river flow and groundwater recharge, affecting the availability of water. There have been many studies of the impact of climate change on river flows in the UK, but coverage has been uneven and methods have varied. Consequently, it has been very difficult to compare different locations and hard to identify appropriate adaptation responses

Capacitors can radiate - some consequences of the two-capacitor problem with radiation

We fill a gap in the arguments of Boykin et al [American Journal of Physics, Vol 70 No. 4, pp 415-420 (2002)] by not invoking an electric current loop (i.e. magnetic dipole model) to account for the radiation energy loss, since an obvious corollary of their results is that the capacitors should radiate directly even if the connecting wires are shrunk to zero length. That this is so is shown here by a direct derivation of capacitor radiation using an oscillating electric dipole radiator model for the capacitors as well as the alternative less widely known magnetic 'charge' current loop representation for an electric dipole [see for example "Electromagnetic Waves" by S.A.Schlekunoff, van Nostrand (1948)]. Implications for Electromagnetic Compliance (EMC) issues as well as novel antenna designs further motivate the purpose of this paper.Comment: 5 Pages with No figure

Examining successful recuritment strategies utilized by volunteer alumni

The purpose of this phenomenological qualitative study was to describe the manner in which volunteer alumni recruiters at a flagship institution were able to recruit prospective students both in and out of the formal recruitment setting. Due to the challenges facing Louisiana State University with out-of-state recruitment, volunteer alumni recruiters provide a cost-effective alternative to assist this effort. Findings of this study can be used to expand the current alumni volunteer recruitment effort by providing insight into the strategies that result in success in the recruitment process, all the while encouraging fellow alumni to assist their effort. The methodology for this study was a one-time, in-depth informal audio taped interview of purposely selected volunteer alumni recruiters. Saturation of the data was determined after six interviews. The following themes emerged from this method: motivation for involvement, volunteer training programs, social networking, minority recruitment, recruitment of new volunteers, recognition, other forms of recruitment efforts, parental involvement, the use of the internet for recruitment, and the reliance on the Division of Outreach as a tool in the recruitment effort. Findings from this study revealed the following: volunteer alumni are motivated because of their passion for the University; many began their recruiting efforts without formal training; volunteer recruiters are able to network interest in different community settings; many reach out to communities labeled as under-privileged, but they do not approach the recruitment process differently; volunteer recruiters solicit fellow alumni to join the effort, and have no trouble retaining them; many gain feedback from students as to why they would not attend LSU, but are rarely given feedback concerning the recruitment effort of the Division of Outreach. Implications for research are to increase qualitative and quantitative studies of volunteer alumni recruiters to establish a framework of the fundamental approach that these individuals take inside and outside the formal recruiting setting. Further research should discuss the manner in which these individuals solicit other volunteer recruiters, and examine motivations and expectations of those who become involved. The social networking ability of these volunteer alumni recruiters is important for a university that is spreading its “footprint” to understand

Regionalised impacts of climate change on flood flows: rationale for definition of climate change scenarios and sensitivity framework. Milestone report 2. Revised November 2009

The primary objective of FD2020 ‘Regionalising the impacts of climate change on flood flows’ was to assess the suitability of current FCDPAG3 guidance given the advances in climate change science since its publication. PAG3 requires an allowance of 20% to be added to peak flows for any period between 2025 and 2115 for any location across Britain. This guidance was considered a precautionary value and its derivation reflected the evidence available at that time. FD2020 has been designed to increase this evidence base, and it is anticipated that the research will lead to the development of regional, rather than national, guidelines for changes to peak flows due to climate change. A scenario-neutral approach based on a broad sensitivity analysis to determine catchment response to changes in climate as chosen for FD2020. The method separates the climate change that a catchment may be exposed to (the hazard) from the catchment response (change in peak flows) to changes in the climate (the vulnerability). By combining current understanding of climate change likelihood (the ‘hazard’) with the vulnerability of a given catchment, it is possible to evaluate the risk of flood flow changes. The vulnerability of a catchment is to be characterised in two steps: first, the response of a set of catchment’s to a range of climatic changes are modelled, then analysed for similarity, and characterised according to catchment properties. This is done by defining a sensitivity framework of changes to the mean and seasonality of precipitation and temperature and modelling the response of each catchment within this fixed framework. To properly understand the relationship between catchment properties, climate changes and changes in flood flows, it is essential that the considered scenarios capture the range of potential climatic changes expected to occur in Great Britain, including the large GCM (Global Climate Model) uncertainty. This means the vulnerability assessment (or the conclusions of the modelling exercise and regionalisation study) will be as robust as possible, and provide a sound science-base for subsequent policy guidance to the flood management community. This project report describes the rationale and the development of the climate change scenarios used in the project FD2020. The objective of this module of work was to develop a methodology to conceptualise how a catchment’s vulnerability (in terms of change in its flood regime under climate change) could be evaluated. This requires the identification of a range of climate change scenarios to be used in a comprehensive yet manageable evaluation of future river flood flows, which was guided by, but not limited to, current predictions of future climatic changes. This methodology is also designed to characterise the climatic change hazard, so that it can be compared with the catchments vulnerability to changes. Previous climate change studies relied only on projections from a few global (GCM) and regional climate models (RCMs), and thus could only capture a very limited part of the GCM uncertainty. The IPCC AR4 now provides data from 17 GCMs, all considered equally plausible representations of future climates

Regionalisation of climate impacts on flood flows to support the development of climate change guidance for Flood Management

Current Defra / Environment Agency guidance (FCDPAG3 supplementary note: http://www.defra.gov.uk/environ/fcd/pubs/pagn/climatechangeupdate.pdf) requires all flood management plans to allow for climate change by incorporating, within a sensitivity analysis, an increase in river flows of up 20% over the next 50 years, and beyond. This guidance is the same for all of England and Wales, making no allowance for regional variation in climate change or catchment type. This reflects the lack of scientific evidence to resolve the spatial distribution of potential impacts on flood flows with enough confidence to set such policy regionally. The 20% allowance was first raised in 1999 for MAFF and subsequently reviewed following the release of the UKCIP02 scenarios. Although the 20% figure is a memorable precautionary target, there is the risk that it leads to a significant under- or over-estimation of future flood risk in individual catchments. Defra and the Environment Agency procured project FD2020 (Regionalisation of climate change impacts on flood flows) to provide a more rigorous science base for refreshing the FCDPAG3: supplementary note guidance. The FD2020 approach is exploring the relationships between catchment characteristics and climate change impacts on peak flows in a “scenario neutral” way. This is done by defining a regular set of changes in climate that encompass all the current knowledge from the new scenarios available from the IPCC Fourth Assessment Report. For each of the 155 catchments included in the research, this broad approach will provide multiple scenarios to produce a “vulnerability surface” for change in the metrics of peak flows (e.g. the 20-year flood flow). Some of the UKCP09 products have also been used to understand what these projections may mean for changes to peak flow. The catchment-based analysis will be used to generalise to other gauged sites across Britain, using relationships with catchment characteristics, providing the scientific evidence for the development of regional guidance on climate change allowances. Specifically the project is: Investigating the impact of climate change on peak river flows in over 150 catchments across Britain to assess the suitability of the FCDPAG3 20% climate change allowance. Investigating catchment response to climate change to identify potential similarities such that the FCDPAG3 nationwide allowance could be regionalised. Investigating the uncertainty in changes to future peak river flows from climate change. Developing an approach that has longevity beyond the project timeframe and the lifetime of the latest generation of climate model results

On the treatment of boundary conditions for bond-based peridynamic models

In this paper, we propose two approaches to apply boundary conditions for bond-based peridynamic models. There has been in recent years a renewed interest in the class of so-called non-local models, which include peridynamic models, for the simulation of structural mechanics problems as an alternative approach to classical local continuum models. However, a major issue, which is often disregarded when dealing with this class of models, is concerned with the manner by which boundary conditions should be prescribed. Our point of view here is that classical boundary conditions, since applied on surfaces of solid bodies, are naturally associated with local models. The paper describes two methods to incorporate classical Dirichlet and Neumann boundary conditions into bond-based peridynamics. The first method consists in artificially extending the domain with a thin boundary layer over which the displacement field is required to behave as an odd function with respect to the boundary points. The second method resorts to the idea that peridynamic models and local models should be compatible in the limit that the so-called horizon vanishes. The approach consists then in decreasing the horizon from a constant value in the interior of the domain to zero at the boundary so that one can directly apply the classical boundary conditions. We present the continuous and discrete formulations of the two methods and assess their performance on several numerical experiments dealing with the simulation of a one-dimensional bar