Problems in RMSE-based wave model validations

In order to evaluate the reliability of numerical simulations in geophysical applications it is necessary to pay attention when using the root mean square error (RMSE) and two other indicators derived from it (the normalized root mean square error (NRMSE), and the scatter index (SI)). In the present work, in fact, we show on a general basis that, in conditions of constant correlation coefficient, the RMSE index and its variants tend to be systematically smaller (hence identifying better performances of numerical models) for simulations affected by negative bias. Through a geometrical decomposition of RMSE in its components related to the average error and the scatter error it can be shown that the above mentioned behavior is triggered by a quasi-linear dependency between these components in the neighborhood of null bias. This result suggests that smaller values of RMSE, NRMSE and SI do not always identify the best performances of numerical simulations, and that these indicators are not always reliable to assess the accuracy of numerical models. In the present contribution we employ the corrected indicator proposed by Hanna and Heinold (1985) to develop a reliability analysis of wave generation and propagation in the Mediterranean Sea by means of the numerical model WAVEWATCH III®, showing that the best values of the indicator are obtained for simulations unaffected by bias. Evidences suggest that this indicator provides a more reliable information about the accuracy of the results of numerical models. © 2013 Elsevier Ltd

Global warming and windstorm impacts in the EU

Windstorms are amongst the most damaging natural hazards in Europe, with approximately 5 €billion of estimated annual losses in the EU. The number of reported windstorms significantly increased over the last decades, yet there is no consensus about a climate-induced trend in windstorms over Europe. Climate model projections of extreme wind are highly uncertain, but they suggest that windstorms will not become more intense or happen more frequent with global warming over most of the European land. As a consequence, it is expected that risks from windstorms in the EU will not rise due to climate change. Future impacts of wind extremes could be reduced by a range of measures, such as the development and implementation of enhanced windstorm-resilient standards and building codes.JRC.E.1-Disaster Risk Managemen

Time-clustering of wave storms in the Mediterranean Sea

In this contribution we identify storm time-clustering in the Mediterranean Sea through a comprehensive analysis of the Allan Factor. This parameter is evaluated from long time series of wave height provided by oceanographic buoy measurements and hindcast re-analysis of the whole basin, spanning the period 1979-2014 and characterized by a horizontal resolution of about 0.1 degree in longitude and latitude and a temporal sampling of one hour (Mentaschi et al., 2015). The nature of the processes highlighted by the AF and the spatial distribution of the parameter are both investigated. Results reveal that the Allan Factor follows different curves at two distinct time scales. The range of time scales between 12 hrs to 50 days is characterised by a departure from the Poisson distribution. For timescales above 50 days, a cyclic Poisson process is identified. The spatial distribution of the Allan Factor reveals that the clustering at smaller time scales is present in the North-West of the Mediterranean, while seasonality is observed in the whole basin. This analysis is believed to be important to assess the local increased flood and coastal erosion risks due to storm clustering

Database on coastal vulnerability and exposure

In this document, we report progress on the development of European layers on exposure and vulnerability. This involves the collection and cataloguing of relevant exposure factors (e.g., land use, population, settlements, infrastructures) and vulnerability indicators (coastal flood protection, damage functions) as well as the development and application of tools for the logging, spatial interpolation, statistical analysis and validation of the collected information. All data are available through the The Risk Data hub database the aim of which is to improve the accessibility and dissemination of EU-wide curated risk data for fostering Disaster Risk Management (DRM).JRC.E.1-Disaster Risk Managemen

PESETA III – Task 8: Coastal Impacts

The present document reports the outcome of efforts envisaging (i) to develop an integrated risk assessment tool LISCoAsT (Large scale Integrated Sea-level and Coastal Assessment Tool) for Europe; and (ii) to perform a pilot study on coastal risk along the European coastline in view of climate change. The overall approach builds on the disaster risk methodology proposed by the IPCC SREX (2012) report, defining risk as the combination of hazard, exposure and vulnerability. Substantial effort has been put in all three individual components of the risk assessment chain. We detail progress in the methodological approach and present the main outcomes of the study, namely projections of coastal hazards, exposure and impacts in Europe. We further provide a foresight of further research needs for coastal zone impact assessment and risk reduction strategies. By the end of this century sea levels in Europe are projected to rise on average between 45 and 70 cm, with regional variations in relative sea level rise. We find that by the end of this century the 100-year event ESL along Europe’s coastlines will on average increase by 57 cm for RCP4.5 and 81 cm for RCP8.5. The North Sea region will face the highest increase in ESLs, amounting to nearly 1 m under RCP8.5 by 2100, followed by the Baltic Sea and Atlantic coasts of the UK and Ireland. Relative Sea Level Rise (RSLR) is the main driver of the projected rise in ESL, with increasing dominance towards the end of the century and for the high-concentration pathway. Changes in storm surges and waves enhance the effects of RSLR along the majority of northern European coasts, locally with contributions up to 40%. In southern Europe, episodic extreme events tend to stay stable, except along the Portuguese coast and the Gulf of Cadiz where reductions in surge and wave extremes offset RSLR by 20-30%. By the end of this century, 5 million Europeans currently under threat of a 100-year ESL could be annually at risk from coastal flooding.JRC.E.1-Disaster Risk Managemen

PESETA III - Task 8: Coastal Impacts - JRC PESETA III project

The study focuses on direct impacts of coastal flooding. Under present climate conditions, the estimated Expected Annual Damage (EAD) for Europe is 1.25 billion €, while the Expected Annual number of People Affected by coastal flooding (EAPA) equals 102,000 people. Under the static economic analysis, EAD is projected to rise to nearly 4 billion € by 2030 and to more than 6 billion € by mid-century (respectively 6.6 and 8.1 billion € for RCP4.5 and RCP8.5). For this scenario, EAPA will rise to nearly 300,000 people by 2030 and exceed 450,000 people (respectively 467,000 and 558,800 people for RCP4.5 and RCP8.5). In the second halve of the century the figures diverge more strongly between the two RCPs. By 2080, due to the effects of climate change only, EAD (EAPA) could rise to 17 billion € (975,000 people) under RCP4.5 and to 28 billion € (1.35 million people) under RCP8.5. Accelerating Sea Level Rise towards the end of the century results in an exponential increase in coastal flood impacts towards the end of the century, with by the year 2100 EAD (EAPA) amounting to 27 billion € (1.3 million people) and 60 billion € (2.1 million people) under RCP4.5 and RCP8.5, respectively. Impacts at 2˚C warming are similar to those around 2050, but are larger under the RCP4.5 scenario compared to RCP8.5. This is related to inertia effects of global warming on SLR. Because the rate of warming is higher under RCP8.5, with 2˚C warming occurring around 2043, the effect of SLR are less pronounced compared to RCP4.5, for which 2˚C warming is projected around 2057. Nevertheless, at any specific point in time, impacts under RCP8.5 are always larger that under RCP4.5.JRC.E.1-Disaster Risk Managemen

Assessment of global wave models on regular and unstructured grids using the Unresolved Obstacles Source Term

The Unresolved Obstacles Source Term (UOST) is a general methodology for parameterizing the dissipative effects of subscale islands, cliffs, and other unresolved features in ocean wave models. Since it separates the dissipation from the energy advection scheme, it can be applied to any numerical scheme or any type of mesh. UOST is now part of the official release of WAVEWATCH III, and the freely available packagealphaBetaLabautomates the estimation of the parameters needed for the obstructed cells. In this contribution, an assessment of global regular and unstructured (triangular) wave models employing UOST is presented. The results in regular meshes show an improvement in model skill, both in terms of spectrum and of integrated parameters, thanks to the UOST modulation of the dissipation with wave direction, and to considering the cell geometry. The improvement is clear in wide areas characterized by the presence of islands, like the whole central-western Pacific Basin. In unstructured meshes, the use of UOST removes the need of high resolution in proximity of all small features, leading to (a) a simplification in the development process of large scale and global meshes, and (b) a significant decrease of the computational demand of accurate large-scale models

Impact of a changing climate, land use, and water usage on water resources in the Danube river basin

Impact of a changing climate, land use, and water usage on water resources in the Danube river basinJRC.D.2-Water and Marine Resource

Climate change and Europe’s water resources

In addition to the already existing pressure on our freshwater resources, climate change may further decrease water availability. In this study, projections of future water resources, due to climate change, land use change and changes in water consumption have been assessed using JRC’s LISFLOOD water resources model. The results presented are based on 11 climate models which project current and future climate under two Representative Concentration Pathways (RCPs): RCP4.5 and RCP 8.5 emission scenario. RCP4.5 may be viewed as a moderate-emissions-mitigation-policy scenario and RCP8.5 as a high-end emissions scenario. A 30-year window around the year that global warming reaches 1.5oC, 2oC and 3oC above preindustrial temperature has been analysed and compared to the 1981-2010 control climate window (baseline). The 1.5°C and 2°C warming scenarios are explicitly considered in the Paris Agreement, while a 3°C global warming is a scenario that could be expected by the end of the 21st century if adequate mitigation strategies are not taken. First, we performed future projections without socio-economic developments to show the effect of climate change only. Next, an integrated assessment is performed including future changes in land use, water demand and population. This allows us to disentangle the effects of climate and socio-economic changes. In general, the climate projections reveal a typically North-South pattern across Europe for water availability. Overall, Southern European countries are projected to face decreasing water availability, particularly Spain, Portugal, Greece, Cyprus, Malta, Italy and Turkey. Central and Northern European countries show an increasing annual water availability.JRC.D.2-Water and Marine Resource

Adapting to rising coastal flood risk in the EU under climate change

Around one third of the EU population lives within 50 km of the coast. Extreme sea levels in Europe could rise by as much as one meter or more by the end of this century. Without mitigation and adaptation measures, annual damages from coastal flooding in the EU-28 could increase sharply from €1.4 billion nowadays to almost €240 billion by 2100. Around 95% of these impacts could be avoided through moderate mitigation and by raising dykes where human settlements and economically important areas exist along the coastline. The extent to which adaptation can lessen the effects of coastal flooding and at what cost is sensitive to the investment strategy adopted.JRC.E.1-Disaster Risk Managemen