Schalk Jan van Andel

Visualizing probabilistic flood forecast information: expert preferences and perceptions of best practice in uncertainty communication

The aim of this article is to improve the communication of the probabilistic flood forecasts generated by hydrological ensemble prediction systems (HEPS) by understanding perceptions of different methods of visualizing probabilistic forecast information. This study focuses on interexpert communication and accounts for differences in visualization requirements based on the information content necessary for individual users. The perceptions of the expert group addressed in this study are important because they are the designers and primary users of existing HEPS. Nevertheless, they have sometimes resisted the release of uncertainty information to the general public because of doubts about whether it can be successfully communicated in ways that would be readily understood to nonexperts. In this article, we explore the strengths and weaknesses of existing HEPS visualization methods and thereby formulate some wider recommendations about the best practice for HEPS visualization and communication. We suggest that specific training on probabilistic forecasting would foster use of probabilistic forecasts with a wider range of applications. The result of a case study exercise showed that there is no overarching agreement between experts on how to display probabilistic forecasts and what they consider the essential information that should accompany plots and diagrams. In this article, we propose a list of minimum properties that, if consistently displayed with probabilistic forecasts, would make the products more easily understandable. Copyright

Spatio-temporal assessment of meteorological drought under the influence of varying record length: the case of Upper Blue Nile Basin, Ethiopia

Abstract This study investigates the spatial and temporal variation of meteorological droughts in the Upper Blue Nile (UBN) basin in Ethiopia using long historical records (1953–2009) for 14 meteorological stations, and relatively short records (1975–2009) for 23 other stations. The influence of using varying record length on drought category was studied by comparing the Standard Precipitation Index (SPI) results from the 14 stations with long record length, by taking out incrementally 1-year records from 1953 to 1975. These analyses show that the record length from 1953 to 1975 has limited effect on changing the drought category and hence the record length from 1975 to 2009 could be used for drought analysis in the UBN basin. Spatio-temporal analyses of the SPI values show that throughout the UBN basin seasonal or annual meteorological drought episodes occurred in the years 1978/79, 1984/85, 1994/95 and 2003/04. Persistency from seasonal to annual drought, and from one year to the next, has been found. The drought years identified by this SPI analysis for the UBN basin are known for their devastating impact in other parts of Ethiopia. Editor Z.W. Kundzewicz; Guest editor D. Hughes

Ensemble Precipitation and Water-Level Forecasts for Anticipatory Water-System Control

Abstract A method is presented for testing weather forecast products for applications in anticipatory water-system control. The applicability of the ensemble prediction system (EPS) of the ECMWF is tested for flood control in a regional water system in the Netherlands. By performing long-term verification analyses, a full range of probability-threshold-based decision rules to apply anticipatory control actions is evaluated in terms of hits (correct alerts), missed events, and false alarms. The analysis includes forecast horizons from 3 to 9 days for extreme precipitation events and extreme water-level events. The water-level forecasts are prepared by feeding each member of the ECMWF EPS precipitation ensemble into a deterministic water-system control model. The current operational strategy is modeled to forecast when the routine operational control will not be sufficient to prevent high water levels, and therefore anticipatory control actions are needed. The results show that ECMWF EPS precipitation forec...

An Experiment on Risk-Based Decision-Making in Water Management Using Monthly Probabilistic Forecasts

AbstractThe use of probabilistic forecasts is necessary to take into account uncertainties and allow for optimal risk-based decisions in streamflow forecasting at monthly to seasonal lead times. Such probabilistic forecasts have long been used by practitioners in the operation of water reservoirs, in water allocation and management, and more recently in drought preparedness activities. Various studies assert the potential value of hydrometeorological forecasting efforts, but few investigate how these forecasts are used in the decision-making process. Role-playing games can help scientists, managers, and decision-makers understand the extremely complex process behind risk-based decisions. In this paper, we present an experiment focusing on the use of probabilistic forecasts to make decisions on reservoir outflows. The setup was a risk-based decision-making game, during which participants acted as water managers. Participants determined monthly reservoir releases based on a sequence of probabilistic inflow ...

A Stratified Sampling Approach for Improved Sampling from a Calibrated Ensemble Forecast Distribution

AbstractBefore using the Schaake shuffle or empirical copula coupling (ECC) to reconstruct the dependence structure for postprocessed ensemble meteorological forecasts, a necessary step is to sample discrete samples from each postprocessed continuous probability density function (pdf), which is the focus of this paper. In addition to the equidistance quantiles (EQ) and independent random (IR) sampling methods commonly used at present, the stratified sampling (SS) method is proposed. The performance of the three sampling methods is compared using calibrated GFS ensemble precipitation reforecasts over the Xixian basin in China. The ensemble reforecasts are first calibrated using heteroscedastic extended logistic regression (HELR), and then the three sampling methods are used to sample calibrated pdfs with a varying number of discrete samples. Finally, the effect of the sampling method on the reconstruction of ensemble members with preserved space dependence structure is analyzed by using EQ, IR, and SS in E...

Framework for Anticipatory Water Management: Testing for Flood Control in the Rijnland Storage Basin

AbstractAnticipatory water management uses weather forecasts and water system simulation models to take operational water management actions before an event occurs. In this paper a framework consisting of the different steps and challenges of developing and evaluating an anticipatory water management strategy is discussed. The framework makes use of recent developments in ensemble weather forecasting and modeling of controlled water systems. In particular, flexible water-system control models enable simulation of a wide range of control strategies in multiyear hindcast analyses. With the increasing number of archives for weather forecasts and water-system-state variables, and the reduction in computational time resulting from increasing processor speed and parallel computing, hindcast verification analysis will become the basis for development and optimization of new operational water management strategies. The framework is successfully applied to a flood control case study in the Netherlands. Archived en...

Visualizing probabilistic flood forecast information: expert preferences and perceptions of best practice in uncertainty communication: VISUALISING PROBABILISTIC FLOOD FORECAST INFORMATION

The aim of this article is to improve the communication of the probabilistic flood forecasts generated by hydrological ensemble prediction systems (HEPS) by understanding perceptions of different methods of visualizing probabilistic forecast information. This study focuses on interexpert communication and accounts for differences in visualization requirements based on the information content necessary for individual users. The perceptions of the expert group addressed in this study are important because they are the designers and primary users of existing HEPS. Nevertheless, they have sometimes resisted the release of uncertainty information to the general public because of doubts about whether it can be successfully communicated in ways that would be readily understood to nonexperts. In this article, we explore the strengths and weaknesses of existing HEPS visualization methods and thereby formulate some wider recommendations about the best practice for HEPS visualization and communication. We suggest that specific training on probabilistic forecasting would foster use of probabilistic forecasts with a wider range of applications. The result of a case study exercise showed that there is no overarching agreement between experts on how to display probabilistic forecasts and what they consider the essential information that should accompany plots and diagrams. In this article, we propose a list of minimum properties that, if consistently displayed with probabilistic forecasts, would make the products more easily understandable. Copyright