International audienceStudies of children’s knowledge of the Earth have led to very different conclusions: some appear to show that children construct their own, non-scientific ‘theories’ (mental models) of the flat, hollow or dual Earth. Others indicate that many young children have some understanding of the spherical (scientific) Earth, and that their knowledge lacks the coherence of mental models. The reasons for these contrasting views were tested by interviewing French children (N5178) aged 5–11 years and varying the differentmethods used in previous research, namely the types of questions (open and forced-choice), the form of representation (two-dimensional pictures and three-dimensional models), and the method of analysis (the mental model theorists’ coding scheme and a statistical test for associations using MANOVA). Forced-choice questions resulted in higher proportions of scientific answers than open questions, and children appeared to have naı¨ve mental models of the Earth only when the mental model theorists’ coding scheme was used. These findings support the view that children tend to have ‘fragments’ of scientific knowledge, and that naı¨ve mental models of the Earth are methodological artifacts

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IFKIS-Hydro is an information and warning system for hydrological hazards in small-and medium-scale catchments. The system collects data such as weather forecasts, precipitation measurements, water level gauges, discharge simulations and local observations of event-specific phenomena. In addition, IFKIS-Hydro incorporates a web-based information platform, which serves as a central hub for the submission and overview of data. Special emphasis is given to local information. This is accomplished particularly by human observers. In medium-scale catchments, discharge forecast models have an increasing importance in providing valuable information. IFKIS-Hydro was developed in several test regions in Switzerland and the first results of its application are available now. The system is constantly extended to additional regions and may become the standard for warning systems in smaller catchments in Switzerland.

Summary Atmospheric and oceanic flows generate the main perturbations in the Earth’s rotation for periods shorter than about 100 days. Both their own dynamics and the Earth’s response being non‐linear, we expect to find non‐linear low‐dimensional deterministic signatures in filtered time‐series of Earth orientation parameters (EOP). Starting from daily observations of the length of day (LOD) and polar motion components (PMX, PMY) spanning more than 27 years, we apply non‐linear time‐series analysis techniques based on the embedding theory in order to determine the dimensional (this paper) and dynamic (Paper II) characteristics of the sought signal source. Estimates of the time delays required to embed the scalar data time‐series in a pseudo‐phase space E* are obtained from the average mutual information function. They are of 10 days for LOD, 15 days for PMX and 18 days for PMY. The dimension DE* of the embedding space E* then has to be determined to unfold the expected source attractor. We try two independent determinations, based on the percentage of global false neighbours and on the correlation integrals. We obtain embedding dimensions between 5 and 7 for the three EOP time‐series. The robustness of the results with regard to various data contaminations and series degradations is checked throughout. Finally, 3‐D projections of delayed coordinate data vectors are drawn. They are clearly different from stochastic power‐law noise and seem to issue from a smooth dynamical system whose dynamical characteristics are investigated in Paper II.