Search results for "Universe"
showing 10 items of 2171 documents
Rhine flood deposits recorded in the Gallo-Roman site of Oedenburg (Haut-Rhin, France).
2006
13 pages; International audience; From the first to the fourth century AD, the Gallo-Roman town of Oedenburg developed in the alluvial landscape of the southern Upper Rhine Graben. Throughout this period, the landscape mosaic, composed of palaeochannels, stable palaeoislands and river terraces, continued to evolve. A district of this town, situated on a lateral Rhine channel system, was archaeologically excavated. Largescale excavation and cross-section analysis provide evidence of changing fluvial conditions during the period under study. At about AD 20 or earlier, this lateral part of the floodplain, affected by very fine sedimentation, was occupied by moribund marshy palaeochannels. When…
G-CLASS: geosynchronous radar for water cycle science – orbit selection and system design
2019
The mission geosynchronous – continental land atmosphere sensing system (G-CLASS) is designed to study thediurnal water cycle, using geosynchronous radar. Although the water cycle is vital to human society, processes on timescalesless than a day are very poorly observed from space. G-CLASS, using C-band geosynchronous radar, could transform this. Itsscience objectives address intense storms and high resolution weather prediction, and significant diurnal processes such assnow melt and soil moisture change, with societal impacts including agriculture, water resource management, flooding, andlandslides. Secondary objectives relate to ground motion observations for earthquake, volcano, and subs…
Effet du relief sur la variabilité de descripteurs des saisons des pluies en Afrique de l’Est.
2011
6 pages; International audience; Les variations spatiales des différents descripteurs des saisons des pluies tropicales (durée, fréquence et intensitédes pluies…) sont mal connues, notamment en régions accidentées. Elles ont pourtant une réelle incidence agroclimatique.Au Kenya, ces descripteurs sont fortement contraints par la géographie, y compris aux échelles fines. L’exemple du versantest du Mont Kenya montre une gamme de conditions agro-écologiques, sous l’influence du schéma général reliantl’augmentation des pluies avec l’altitude. L’altitude influence principalement la durée des deux saisons des pluies (Long etShort rains). La fréquence des jours de pluies est également modulée par l…
Heat wave occurrences over Senegal during spring: regionalization and synoptic patterns.
2020
18 pages; International audience; Based on 12 Senegalese stations of the Global Summary of the Day (GSOD) database (1979–2014), heat waves (HW) are defined for each station in spring (March–April–May, the hottest season in Senegal) as the daily maximum temperature (Tx), minimum temperature (Tn), or average apparent temperature of the day (AT), exceeding the corresponding 95% mobile percentile for at least three consecutive days. A hierarchical cluster analysis used to regionalize HW in these 12 stations is applied to simultaneous occurrences of daily temperature peaks over their 95% mobile percentiles. Three homogeneous zones of four stations each are identified (Zone 1, Zone 2 and Zone 3),…
Urban Heat Island (UHI) and heat waves: what relations?
2018
With four years of measurements and alarge sample of stations, the MUSTARDijon network allows for a detailed characterization of the Urban HeatIsland (UHI), a warm season phenomenon. But UHI and maximum temperature values are out of phase at twodistinct time-scales. Seasonally, the maxima of UHI occur from May to July, i.e. before the annual peak oftemperature (July to August). At a daily time-scale, analysis of the two heat waves of July 2015 shows a lag of afew days between the peak of UHI and the heat wave. Two hypotheses are suggested to explain these lags:changes in radiative conditions and/or energy fluxes between the ground surface and the atmosphere.
Les vagues de chaleur au Sahel : caractérisation, mécanismes, prévisibilité.
2016
The mechanisms controlling Sahelian heat wave (HW) variability are examined on the period 1979-2014 using the GSOD observational database and ERA-Interim reanalyses. HW events are analyzed through all terms of the atmospheric energy balance, showing a predominant role of incoming shortwave radiation on daily maximum temperature (Tx) and atmospheric water vapor on minimum temperature (Tn). The low-frequency warming trend, not explained by the previous terms, is thought to relate to the increase of greenhouse gases concentrations, due to anthropogenic emissions. The predictability of Sahelian HW events is assessed for lead times reaching up to 15 days. The model's skill, biases and uncertaint…
Les Local Climate Zones face à la canicule de 2018 à Dijon.
2019
Air temperatures measured by the MUSTARDijon network are analyzed during the summer 2018 (July 24 - August 8) heat wave. The WUDAPT method is applied to Dijon to identify Local Climate Zones (LCZs). Diurnal rhythms and nighttime mean temperatures are analyzed according to LCZs as well as to altitude and distance to the city center. During warm nights, altitude plays a negligible role. The temperatures depend to the distance of the city center. They are also associated to the anthropization summarized by the LCZs. Form of the building and vegetation are the two keys to understand and modulate the night temperatures which have the greatest impact on human health during heat waves.
Radar-rain gauges intercomparison for the estimation of high resolution rainfall.
2015
An accurate rainfall estimation is essential for many applications like precision viticulture. Rainfall is most of the time estimated by two methods:radar and rain gauges. High resolution rain gauges network Hydravitis was installed in 2014. Data coming from radar,composite product and the network was extracted for the 2014 3 to 4 November event. Data from the network were kriged tocompare with the other products. Results show that PANTHERE radar image well reproduces the spatial variability ofrainfall but underestimates rainfall amounts over a 4 mm/h intensité. Composite product ANTILOPE gives a goodvisualization of spatial variability and intensity of rainfall. Expectations of viticulture…
Coastal high-frequency radars in the Mediterranean – Part 1: Status of operations and a framework for future development
2022
Due to the semi-enclosed nature of the Mediterranean Sea, natural disasters and anthropogenic activities impose stronger pressures on its coastal ecosystems than in any other sea of the world. With the aim of responding adequately to science priorities and societal challenges, littoral waters must be effectively monitored with high-frequency radar (HFR) systems. This land-based remote sensing technology can provide, in near-real time, fine-resolution maps of the surface circulation over broad coastal areas, along with reliable directional wave and wind information. The main goal of this work is to showcase the current status of the Mediterranean HFR network and the future roadmap for orches…
Coastal high-frequency radars in the Mediterranean - Part 2: Applications in support of science priorities and societal needs
2022
The Mediterranean Sea is a prominent climate-change hot spot, with many socioeconomically vital coastal areas being the most vulnerable targets for maritime safety, diverse met-ocean hazards and marine pollution. Providing an unprecedented spatial and temporal resolution at wide coastal areas, high-frequency radars (HFRs) have been steadily gaining recognition as an effective land-based remote sensing technology for continuous monitoring of the surface circulation, increasingly waves and occasionally winds. HFR measurements have boosted the thorough scientific knowledge of coastal processes, also fostering a broad range of applications, which has promoted their integration in coastal ocean …