Relative impact of model quality and ensemble deficiencies on the performance of ensemble based probabilistic forecasts evaluated through the Brier score

International audienceThe relative impact of model quality and ensemble deficiencies, on the performance of ensemble based probabilistic forecasts, is investigated from a set of idealized experiments. Data are generated according to a statistical model, the validation of which is achieved by comparing generated data to ECMWF ensemble forecasts and analyses. The performance of probabilistic forecasts is evaluated through the reliability and resolution terms of the Brier score. Results are as follows. (i) Resolution appears essentially attributable to the average level of forecast skill. (ii) The lack of reliability comes primarily from forecast bias, and to a lower extent from the ensemble being systematically under-dispersive (or over-dispersive). (iii) Forecast skill contributes very little to reliability in the absence of forecast bias, and this impact is entirely due to the finiteness of the ensemble population. (iv) In the presence of forecast bias, reducing forecast skill leads to improve the reliability. This unexpected feature comes from the fact that lower forecast skill leads to a larger ensemble spread, that compensates for the strong proportion of outliers consequent to forecast bias. (v) The lack of ensemble skill, i.e. non systematic errors affecting both ensemble mean and ensemble spread, contributes little, but significantly, to the lack of reliability and resolution

Challenges and Prospects for the EU’s Area of Freedom, Security and Justice: Recommendations to the European Commission for the Stockholm Programme. CEPS Working Document No. 313, 16 April 2009

The upcoming Swedish presidency of the EU will be in charge of adopting the next multi-annual programme on an Area of Freedom, Security and Justice (AFSJ), during its tenure in the second half of 2009. As the successor of the 2004 Hague Programme, it has already been informally baptised as the Stockholm Programme and will present the EU’s policy roadmap and legislative timetable over these policies for the next five years. It is therefore a critical time to reflect on the achievements and shortcomings affecting the role that the European Commission’s Directorate-General of Justice, Freedom and Security (DG JFS) has played during the last five years in light of the degree of policy convergence achieved so far. This Working Document aims at putting forward a set of policy recommendations for the DG JFS to take into consideration as it develops and consolidates its future policy strategies, while duly ensuring the legitimacy and credibility of the EU’s AFSJ within and outside Europe

Verification of intense precipitation forecasts from single models and ensemble prediction systems

International audienceThe performance of single models and ensemble prediction systems has been investigated with respect to quantitative precipitation forecasts. Evaluation is based on the potential economic value of + 72 h/ + 96 h forecasts. The verification procedure consists of taking into account all precipitation amounts that are predicted in the vicinity of an observation in order to compute spatial, multi-event contingency tables. A probabilistic forecast from an ensemble can thus be compared to a probabilistic forecast from a single model run. The main results are the following: (1) The performance of the forecasts increases with the precipitation threshold. High levels of potential value reflect high hit rates that are obtained at the expense of a high frequency of false alarms. (2) The ECMWF ensemble performs better than a single forecast based on the same model, even when the resolution of the ensemble is lower. This is true for the NCEP ensemble as well, but only for morning precipitations. (3) The ECMWF ensemble performs better than the 5-member NCEP ensemble running at 12:00 UTC, even when the population of the former is reduced to 5 members. (4) The impact of reducing the population of the ECMWF ensemble is rather small. Differences between 51 members and 21 members are hardly significant. (5) A 2-member poorman ensemble consisting of the control forecasts of the ECMWF and the NCEP ensembles performs as well as the ECMWF ensemble for afternoon precipitations

Regulation of Mammalian Physiology by Interconnected Circadian and Feeding Rhythms.

Circadian clocks are endogenous timekeeping systems that adapt in an anticipatory fashion the physiology and behavior of most living organisms. In mammals, the master pacemaker resides in the suprachiasmatic nucleus and entrains peripheral clocks using a wide range of signals that differentially schedule physiology and gene expression in a tissue-specific manner. The peripheral clocks, such as those found in the liver, are particularly sensitive to rhythmic external cues like feeding behavior, which modulate the phase and amplitude of rhythmic gene expression. Consequently, the liver clock temporally tunes the expression of many genes involved in metabolism and physiology. However, the circadian modulation of cellular functions also relies on multiple layers of posttranscriptional and posttranslational regulation. Strikingly, these additional regulatory events may happen independently of any transcriptional oscillations, showing that complex regulatory networks ultimately drive circadian output functions. These rhythmic events also integrate feeding-related cues and adapt various metabolic processes to food availability schedules. The importance of such temporal regulation of metabolism is illustrated by metabolic dysfunctions and diseases resulting from circadian clock disruption or inappropriate feeding patterns. Therefore, the study of circadian clocks and rhythmic feeding behavior should be of interest to further advance our understanding of the prevention and therapy of metabolic diseases

A New Framework for the Assessment and Calibration of Medium Range Ensemble Temperature Forecasts

We present a new framework for the assessment and calibration of medium range ensemble temperature forecasts. The method is based on maximising the likelihood of a simple parametric model for the temperature distribution, and leads to some new insights into the predictability of uncertainty.Comment: Submitted to AS

Nuclear Proteomics Uncovers Diurnal Regulatory Landscapes in Mouse Liver.

Diurnal oscillations of gene expression controlled by the circadian clock and its connected feeding rhythm enable organisms to coordinate their physiologies with daily environmental cycles. While available techniques yielded crucial insights into regulation at the transcriptional level, much less is known about temporally controlled functions within the nucleus and their regulation at the protein level. Here, we quantified the temporal nuclear accumulation of proteins and phosphoproteins from mouse liver by SILAC proteomics. We identified around 5,000 nuclear proteins, over 500 of which showed a diurnal accumulation. Parallel analysis of the nuclear phosphoproteome enabled the inference of the temporal activity of kinases accounting for rhythmic phosphorylation. Many identified rhythmic proteins were parts of nuclear complexes involved in transcriptional regulation, ribosome biogenesis, DNA repair, and the cell cycle and its potentially associated diurnal rhythm of hepatocyte polyploidy. Taken together, these findings provide unprecedented insights into the diurnal regulatory landscape of the mouse liver nucleus

Circadian and Feeding Rhythms Orchestrate the Diurnal Liver Acetylome.

Lysine acetylation is involved in various biological processes and is considered a key reversible post-translational modification in the regulation of gene expression, enzyme activity, and subcellular localization. This post-translational modification is therefore highly relevant in the context of circadian biology, but its characterization on the proteome-wide scale and its circadian clock dependence are still poorly described. Here, we provide a comprehensive and rhythmic acetylome map of the mouse liver. Rhythmic acetylated proteins showed subcellular localization-specific phases that correlated with the related metabolites in the regulated pathways. Mitochondrial proteins were over-represented among the rhythmically acetylated proteins and were highly correlated with SIRT3-dependent deacetylation. SIRT3 activity being nicotinamide adenine dinucleotide (NAD) <sup>+</sup> level-dependent, we show that NAD <sup>+</sup> is orchestrated by both feeding rhythms and the circadian clock through the NAD <sup>+</sup> salvage pathway but also via the nicotinamide riboside pathway. Hence, the diurnal acetylome relies on a functional circadian clock and affects important diurnal metabolic pathways in the mouse liver

Understanding predictive uncertainty in hydrologic modeling: The challenge of identifying input and structural errors

Meaningful quantification of data and structural uncertainties in conceptual rainfall-runoff modeling is a major scientific and engineering challenge. This paper focuses on the total predictive uncertainty and its decomposition into input and structural components under different inference scenarios. Several Bayesian inference schemes are investigated, differing in the treatment of rainfall and structural uncertainties, and in the precision of the priors describing rainfall uncertainty. Compared with traditional lumped additive error approaches, the quantification of the total predictive uncertainty in the runoff is improved when rainfall and/or structural errors are characterized explicitly. However, the decomposition of the total uncertainty into individual sources is more challenging. In particular, poor identifiability may arise when the inference scheme represents rainfall and structural errors using separate probabilistic models. The inference becomes ill‐posed unless sufficiently precise prior knowledge of data uncertainty is supplied; this ill‐posedness can often be detected from the behavior of the Monte Carlo sampling algorithm. Moreover, the priors on the data quality must also be sufficiently accurate if the inference is to be reliable and support meaningful uncertainty decomposition. Our findings highlight the inherent limitations of inferring inaccurate hydrologic models using rainfall‐runoff data with large unknown errors. Bayesian total error analysis can overcome these problems using independent prior information. The need for deriving independent descriptions of the uncertainties in the input and output data is clearly demonstrated.Benjamin Renard, Dmitri Kavetski, George Kuczera, Mark Thyer, and Stewart W. Frank

Assessing the reliability of probabilistic flood inundation model predictions

An ability to quantify the reliability of probabilistic flood inundation predictions is a requirement not only for guiding model development but also for their successful application. Probabilistic flood inundation predictions are usually produced by choosing a method of weighting the model parameter space, but previous study suggests that this choice leads to clear differences in inundation probabilities. This study aims to address the evaluation of the reliability of these probabilistic predictions. However, a lack of an adequate number of observations of flood inundation for a catchment limits the application of conventional methods of evaluating predictive reliability. Consequently, attempts have been made to assess the reliability of probabilistic predictions using multiple observations from a single flood event. Here, a LISFLOOD-FP hydraulic model of an extreme (>1 in 1000 years) flood event in Cockermouth, UK, is constructed and calibrated using multiple performance measures from both peak flood wrack mark data and aerial photography captured post-peak. These measures are used in weighting the parameter space to produce multiple probabilistic predictions for the event. Two methods of assessing the reliability of these probabilistic predictions using limited observations are utilized; an existing method assessing the binary pattern of flooding, and a method developed in this paper to assess predictions of water surface elevation. This study finds that the water surface elevation method has both a better diagnostic and discriminatory ability, but this result is likely to be sensitive to the unknown uncertainties in the upstream boundary conditio