Exploring drought‐to‐flood interactions and dynamics: A global case review

This study synthesizes the current understanding of the hydrological, impact, and adaptation processes underlying drought‐to‐flood events (i.e., consecutive drought and flood events), and how they interact. Based on an analysis of literature and a global assessment of historic cases, we show how drought can affect flood risk and assess under which circumstances drought‐to‐flood interactions can lead to increased or decreased risk. We make a distinction between hydrological, socio‐economic and adaptation processes. Hydrological processes include storage and runoff processes, which both seem to mostly play a role when the drought is a multiyear event and when the flood occurs during the drought. However, which process is dominant when and where, and how this is influenced by human intervention needs further research. Processes related to socio‐economic impacts have been studied less than hydrological processes, but in general, changes in vulnerability seem to play an important role in increasing or decreasing drought‐to‐flood impacts. Additionally, there is evidence of increased water quality problems due to drought‐to‐flood events, when compared to drought or flood events by themselves. Adaptation affects both hydrological (e.g., through groundwater extraction) or socio‐economic (e.g., influencing vulnerability) processes. There are many examples of adaptation, but there is limited evidence of when and where certain processes occur and why. Overall, research on drought‐to‐flood events is scarce. To increase our understanding of drought‐to‐flood events we need more comprehensive studies on the underlying hydrological, socio‐economic, and adaptation processes and their interactions, as well as the circumstances that lead to the dominance of certain processes. This article is categorized under: Science of Water > Hydrological Processes Science of Water > Water Extreme

A Path to the Stars: The Evolution of the Species

During the last years, a number of telescopes have been dedicated to the followup of the GRBs. But after the Swift launch, the average observed intensity of the GRBs showed to be lower than thought before. Our experience with the robotic 60 cm REM telescope confirmed this evidence, with a large number oflostGRBs. Then, we proposed to study the feasibility of a 4 m fast pointing class telescope, equipped with a multichannel imagers, from Visible to Near Infrared. In this paper, we present the main result of the feasibility study we performed so far

NOPT – New polishing techniques for scalable, light-weighted mirrors of different materials

In the framework of an assessment of optical polishing techniques, ESA has signed a contract with Media Lario to deliver two 250 mm mirrors with a common optical design to be polished down to very tight surface requirements. NOPT mirrors are respectively made of Zerodur and AlSi alloy with electroless nickel and will they be polished by means of bonnet polishing. Mirrors are light-weighted up to 20kg/m2; the mechanical and optical design is proven to be scalable up to 1m CA surfaces. This paper reviews the mirrors opto-mechanical design, introduce the polishing and metrology strategy while highlighting the differences and the common point in fabricating such mirror in Zerodur and metal

NOPT – New polishing techniques for scalable, light-weighted mirrors of different materials

In the framework of an assessment of optical polishing techniques, ESA has signed a contract with Media Lario to deliver two 250 mm mirrors with a common optical design to be polished down to very tight surface requirements. NOPT mirrors are respectively made of Zerodur and AlSi alloy with electroless nickel and will they be polished by means of bonnet polishing. Mirrors are light-weighted up to 20kg/m2; the mechanical and optical design is proven to be scalable up to 1m CA surfaces. This paper reviews the mirrors opto-mechanical design, introduce the polishing and metrology strategy while highlighting the differences and the common point in fabricating such mirror in Zerodur and metal

An integral field unit for X-shooter

International audienceX-shooter is a new high-efficiency integral field spectrograph mainly dedicated to the spectroscopic follow up of the gamma ray bursts. X-shooter will operate at the Cassegrain focus of the VLT with an intermediate spectral resolution of ~5000, and will provide a very wide simultaneous spectral coverage, ranging from 320 to 2500 nm. The instrument consists in a central structure which supports three prism cross-dispersed echelle spectrographs respectively optimized for the UV-blue, Visible and Near-IR wavelength ranges. X-shooter will offer an image slicer based Integral Field Unit (IFU) designed to analyse a 1.8"x4" input field into 3 slices of 0.6"x4"and to align then on a 12" long slit. The principle of the IFU is that the central slice does not include any dioptre, the light is directly transmitted to the spectrographs. Only the two lateral sliced fields are reflected toward the two pairs of spherical mirrors and re-aligned at both ends of the previous slice in order to form the exit slit. We present here the IFU design developed at the Observatoire de Paris

On-sky Testing of the Active Phasing Experiment

International audienceThe Active Phasing Experiment (APE) has been used by ESO to gain experience in controlling segmented primary mirrors in preparation for the European Extremely Large Telescope. The experiment tested various phasing techniques and explored their advantages and limitations. Four optical phasing sensors were developed using different techniques — a curvature sensor, a pyramid sensor, a Shack-Hartmann sensor and a sensor based on a modified Mach-Zehnder interferometer. The design of the APE instrument is described. APE was installed at the VLT visitor focus for on-sky testing and a brief summary of the results of the experiment is given

X-shooter: UV-to-IR intermediate-resolution high-efficiency spectrograph for the ESO VLT

International audienc