Search results for "Universe"
showing 10 items of 2171 documents
Les changements futurs de la mousson africaine.
2013
7 pages; International audience; Nous analysons l’effet du changement climatique sur la mousson d’Afrique de l’ouest par l’utilisation de huitmodèles CMIP5 sous scénario RCP4.5, la réalisation d’un multi-modèle et l’approche « one model, one vote ». Les résultatsmontrent l’apparition d’un contraste pluviométrique zonal entre le centre et l’ouest du Sahel. Une mousson plus intensepermettrait une hausse de la convergence d’humidité et des précipitations au centre du Sahel. Un renforcement du jet d’estafricain et de la subsidence sur l’ouest du Sahel y permettrait en revanche une baisse de la pluviométrie.
Contribution des talwegs tropicaux-tempérés aux précipitations d’Afrique australe : quelle évolution dans le cadre du changement climatique ?
2014
6 pages; International audience; Cette étude analyse les changements de la pluviométrie et des talwegs tropicaux-tempérés (TTT) en Afriqueaustrale dans le cadre du changement climatique en utilisant huit modèles climatiques retenus dans l’exercice 5 du GIEC etforcés selon la trajectoire RCP 8.5. Tous les modèles restituent convenablement les bandes nuageuses associées aux TTT,tant en termes de variabilité spatiale que de fréquence d’occurrences. Les modèles divergent sur l’évolution desprécipitations de saison des pluies (NDJF). En revanche, ils montrent tous une diminution du nombre de jours de pluieassociée à une augmentation d’événements plus pluvieux. Ces changements dans la distributio…
Heat in Normandy, types of atmospheric circulation and climate change (1970 - 2019)
2020
Heat in Normandy, synoptic circulation patterns and climate change (1970-2019). This article focuses on the role and the evolution of the different kinds of synoptic circulation patterns in the occurrence of hot days in Normandy. Heat is here, very dependent on the presence of action centres over central Europe as well as, air flow coming from NE and E. Contemporary climate change expresses itself by a rise in thermal efficiency of all synoptic circulation patterns (more heat for the same flow). Lastly, the north of Cotentin stands out by being a real “cool island” during summer because of its peninsula position which imposes on any air mass, regardless of its origin, a cooling from its bot…
Tropical Temperate Toughs over southern Africa: mechanisms and evolution in response to climate change
2015
In the Southern Hemisphere, Southern Africa and the south-west Indian Ocean are one of the three preferred regions where interactions between the tropics and midlatitudes develop. This is the South Indian Convergence Zone (SICZ), where northwest-southeast oriented cloud bands form at the synoptic scale (between 3 and 5 days). These bands are mainly found during the austral summer and are commonly referred to as tropical temperate troughs (TTTs). This research aims at improving our knowledge related to TTTs, with a study on the dynamics associated with these systems, and an analysis of their possible evolution during the 21st century.The first part of this thesis aims at identifying favorab…
Comparative high-resolution chemostratigraphy of the Bonarelli Level from the reference Bottaccione section (Umbria-Marche Apennines) and from an equ…
2006
The Bonarelli Level (BL) from the upper Cenomanian portion of the reference Bottaccione section (central Italy) is characterized by the presence of black shales containing high TOC concentrations (up to 17%) and amounts of CaCO3 near to zero. In the absence of carbonate and, consequently, of relative carbon- and oxygen-isotopic data, the elemental geochemistry revealed to be a very useful tool to obtain information about the palaeoclimatic and palaeoceanographic evolution of the Tethys Ocean during the OAE2. Based on several geochemical proxies (Rb, V, Ni, Cr, Si, Ba), the BL is interpreted as a high-productivity event driven by increasingly warm and humid climatic conditions promoting an a…
Sulfide ore facies, fluid inclusion and sulfur isotope characteristics of the Tappehsorkh Zn-Pb ( ± Ag-Ba) deposit, South Esfahan, Iran
2020
International audience; The stratiform, stratabound Tappehsorkh Zn-Pb (± Ag-Ba) deposit, located in the southeastern part of the Malayer-Esfahan Metallogenic Belt of Iran, formed during Lower Cretaceous back-arc extension. Sulfide mi-neralization occurs within dolostone, black siltstone, and crystal lithic tuff and andesite associated with the Gushfil-Baghabrisham synsedimentary normal fault. Three sulfide ore facies (massive, bedded, and stockwork) occur in the deposit. Sulfide minerals are sphalerite, galena, tetrahedrite and pyrite with minor chalcopyrite and bornite, and gangue minerals are barite, dolomite and quartz. Sulfide mineralization textures are massive, replacement , vein-vein…
Le changement climatique : où en sommes-nous ?
2018
Greenhouse gases (GHGs), naturally part of the atmosphere, have protected us from severe glaciations in the past. Today, human activities increase GHG concentrations and cause rapid and unprecedented Earth warming. Climate change is not resume only to warming, water cycle is also changed. All the research confirms: the climate is changing fast, too fast for ecosystems and societies to adapt. Despite the alerts of the international scientific community, States gathered into Conferences of the Parties (COP) ratify agreements but do not comply with all their commitments. Public opinion polls indicate that climate change is perceived as a risk, but jobs and taxes override environmental concerns…
Hafnium-neodymium isotope evidence for enhanced weathering and tectonic-climate interactions during the Late Cretaceous
2022
<p>Over million-year timescale the carbon cycle evolution is driven by mantle CO<sub>2</sub> degassing (source) and by continental weathering that drawdowns atmospheric CO<sub>2</sub> through silicate weathering reactions (sink). Based on a novel geochemical proxy of chemical weathering intensity (i.e. using measurements of Hf and Nd isotope ratios in clay-size fractions of sediments) and clay mineralogy, we discuss the links between tectonic, continental weathering and climate evolution during the late Cretaceous. That period records the very first step of the last greenhouse to icehouse transition and is concomitant to …
État actuel des réseaux de mesures éco-climatiques en Afrique centrale : les ambitions du projet de recherche international FORGREENE.
2016
This work presents an overview of spatio-temporal quality andspatial density of rainfall networks of Cameroon, Gabon, Congo, CAP and DRC, particularly in the recentperiod (1973-2014) through the GSOD international database. Faced with enormous gaps observed, theseresults will help to select metrological and analytical orientations in FORGREENE project (Tropical forestsgreeness and cloudiness in Central Africa: present conditions and future evolution). A comparison with rainfallsatellite estimates (RFE type) also indicates their great potential, provided they are based on in situ validations.
Climate change of Benin for the period 1950-2010 and its impact on surface water.
2016
6 pages; International audience; In West Africaand Benin in particular, variability / climate change affects the availability of surface water resources. Thus,this study aims to analyze the rainfall field of Benin from the fifty three (53) meteorological stations from 1950to 2010 and to detect the rainfall amounts and the average temperature of six synoptic stations and thehydrometric stations of Niger river in, Benin, Pendjari, Ouémé, Mono and Couffo. From the analysis a trend ofdeclining precipitation and of rising temperatures have been highlighted. This decrease is more pronounced inthe Sudanese area (north of 8 ° N) and in the sub-equatorial area (south of 8 ° N). This decrease of prec…