Less frequent and more intense rainfall along the coast of the Gulf of Guinea in West and Central Africa (1981-2014)

Since the 1990s, rainfall has been reported to increase over the Gulf of Guinea. In light of the devastating floods that have occurred since then over the coastal areas of this region, this study aims to better characterize the recent trends in precipitation there. We used the Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) product, a new observational rainfall dataset that covers the period 1981-2014 at high resolution and daily time steps. During the first rainy season (April-June), we find that the lack of significant trend observed in mean precipitation hides a trend towards less frequent but more intense rainfall along the coast of the Gulf of Guinea, which is expected to increase the likelihood of flooding and droughts, and fits with the recent increase in devastating floods. Over the north however (between 7 degrees and 12.5 degrees N), rainfall has become more frequent and less intense, which is expected to decrease the likelihood of flooding and droughts. During the second rainy season (September-November), we find that the clear increase in mean precipitation observed between 5 degrees and 12.5 degrees N results from an increase in precipitation intensity and frequency, while over southern Cameroon, the decrease in mean precipitation hides a trend towards less frequent but more intense rainfall. In both seasons, the average duration of wet spells has greatly decreased along the coast, in favor of more numerous and more intense isolated wet days

ROLE DE LA PAROI PRIMAIRE ET DU CYTOSQUELETTE DANS L'ELONGATION CELLULAIRE CHEZ ARABIDOPSIS THALIANA (CARACTERISATION DES MUTANTS KORRIGAN ET BOTEROL)

AU COURS D'UN CRIBLAGE DE MUTANTS A HYPOCOTYLE COURT ET EXPANSION RADIALE EXAGEREE, LES MUTANTS KORRIGAN ET BOTEROL ONT PU ETRE ISOLES. LES PREMIERES ETUDES ONT MONTRE QUE LE KOR ETAIT UNE ENDO-1, 4-D-GLUCANASES MEMBRANAIRES NECESSAIRE A L'ELONGATION CELLULAIRE ET L'ORGANISATION DE LA PAROI (NICOL ET AL., 1998) EN OUTRE, NOUS AVONS MONTRE QUE KOR ETAIT DEFICIENT EN CELLULOSE. LE NIVEAU DE PROTEINES KOR EST EN CORRELATION AVEC L'ELONGATION CELLULAIRE ET LE DEPOT DE LA PAROI PRIMAIRE, AINSI QU'AVEC LE DEPOT DE LA PAROI SECONDAIRE. DE PLUS, IL EXISTE UNE REGULATION TRANSCRIPTIONNELLE OU POST-TRANSCRIPTIONNELLE DE KOR1 DANS UN MUTANT THERMOSENSIBLE DEFICIENT POUR UNE SOUS-UNITE CATALYTIQUE DE LA CELLULOSE SYNTHASE, RSW1. CES DONNEES CONFORTAIENT L'HYPOTHESE SELON LAQUELLE KOR SERAIT IMPLIQUEE DANS LA BIOSYNTHESE DE CELLULOSE. CEPENDANT, GRACE A LA TECHNIQUE D'IMMUNOLOCALISATION, NOUS AVONS DECOUVERT QUE LA PROTEINE KOR1 ETAIT LOCALISEE DANS DES ORGANITES INTRACELLULAIRES DIFFERENTS DU RETICULUM DE L'APPAREIL DE GOLGI ET NE COLOCALISE PAS AVEC LA SACCHAROSE SYNTHASE. CECI SUGGERE QUE KOR POURRAIT NE PAS ETRE DIRECTEMENT IMPLIQUE DANS LE COMPLEXE DE SYNTHESE DE CELLULOSE SUR LA MEMBRANE PLASMIQUE. LES MUTANTS AU LOCUS BOTERO1 SONT AFFECTES DANS LA CROISSANCE ANISOTROPIQUE DANS TOUS LES TYPES CELLULAIRES A CROISSANCE NON-APICALE EXAMINES. GRACE AU MARQUAGE DES MICROTUBULES PAR DES TECHNIQUES D'IMMUNOFLUORESCENCE, J'AI PU DEMONTRER QUE LE DEFAUT D'EXPANSION CELLULAIRE DE BOTERO1 ETAIT CORRELE AVEC UN DEFAUT D'ORIENTATION DES MICROTUBULES CORTICAUX EN UN RESEAU TRANSVERSE APRES ARRET DE LA MITOSE. NOS OBSERVATIONS SUGGERENT QUE BOT1 EST NECESSAIRE A L'ORGANISATION DES MICROTUBULES CORTICAUX EN RESEAUX TRANSVERSES DANS LES CELLULES EN INTERPHASE AFIN DE MAINTENIR LA DIRECTION DE L'EXPANSION CELLULAIRE. LE CLONAGE RECENT DU GENE A MONTRE QU'IL A DE FORTES HOMOLOGIES AVEC LA SOUS-UNITE P60 DE LA PROTEINE DE COUPURE DES MICROTUBULES KATANIN.PARIS-BIUSJ-Thèses (751052125) / SudocCentre Technique Livre Ens. Sup. (774682301) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Less frequent and more intense rainfall along the coast of the Gulf of Guinea in West and Central Africa (1981-2014)

Since the 1990s, rainfall has been reported to increase over the Gulf of Guinea. In light of the devastating floods that have occurred since then over the coastal areas of this region, this study aims to better characterize the recent trends in precipitation there. We used the Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) product, a new observational rainfall dataset that covers the period 1981-2014 at high resolution and daily time steps. During the first rainy season (April-June), we find that the lack of significant trend observed in mean precipitation hides a trend towards less frequent but more intense rainfall along the coast of the Gulf of Guinea, which is expected to increase the likelihood of flooding and droughts, and fits with the recent increase in devastating floods. Over the north however (between 7 degrees and 12.5 degrees N), rainfall has become more frequent and less intense, which is expected to decrease the likelihood of flooding and droughts. During the second rainy season (September-November), we find that the clear increase in mean precipitation observed between 5 degrees and 12.5 degrees N results from an increase in precipitation intensity and frequency, while over southern Cameroon, the decrease in mean precipitation hides a trend towards less frequent but more intense rainfall. In both seasons, the average duration of wet spells has greatly decreased along the coast, in favor of more numerous and more intense isolated wet days

Intensification of the hydrological cycle expected in West Africa over the 21st century

This study uses the high-resolution outputs of the recent CORDEX-Africa climate projections to investigate the future changes in different aspects of the hydrological cycle over West Africa. Over the twenty-first century, temperatures in West Africa are expected to increase at a faster rate (+0.5 degrees C per decade) than the global average (+0.3 degrees C per decade), and mean precipitation is expected to increase over the Guinea Coast (+0.03 mm d(-1) per decade) but decrease over the Sahel (-0.005 mm d(-1) per decade). In addition, precipitation is expected to become more intense (+0.2 mm d(-1) per decade) and less frequent (-1.5 d per decade) over all of West Africa as a result of increasing regional temperature (precipitation intensity increases on average by +0.35 mm d(-1) degrees C-1 and precipitation frequency decreases on average by -2.2 d degrees C -1). Over the Sahel, the average length of dry spells is also expected to increase with temperature (+4 % d degrees C-1), which increases the likelihood for droughts with warming in this subregion. Hence, the hydrological cycle is expected to increase throughout the twenty-first century over all of West Africa, on average by +11 % degrees C-1 over the Sahel as a result of increasing precipitation intensity and lengthening of dry spells, and on average by +3 % degrees C-1 over the Guinea Coast as a result of increasing precipitation intensity only

Global precipitation response to changing forcings since 1870

Predicting and adapting to changes in the hydrological cycle is one of the major challenges for the 21st century. To better estimate how it will respond to future changes in climate forcings, it is crucial to understand how the hydrological cycle has evolved in the past and why. In our study, we use an atmospheric global climate model with prescribed sea surface temperatures (SSTs) to investigate how, in the period 1870–2005, changing climate forcings have affected the global land temperature and precipitation. We show that between 1870 and 2005, prescribed SSTs (encapsulating other forcings and internal variability) determine the decadal and interannual variabilities of the global land temperature and precipitation, mostly via their influence in the tropics (25° S–25° N). In addition, using simulations with prescribed SSTs and considering the atmospheric response alone, we find that between 1930 and 2005 increasing aerosol emissions have reduced the global land temperature and precipitation by up to 0.4 °C and 30 mm yr−1, respectively, and that between about 1950 and 2005 increasing greenhouse gas concentrations have increased them by up to 0.25 °C and 10 mm yr−1, respectively. Finally, we suggest that between about 1950 and 1970, increasing aerosol emissions had a larger impact on the hydrological cycle than increasing greenhouse gas concentrations.ISSN:1680-7375ISSN:1680-736

Potential impact of climate change on solar resource in Africa for photovoltaic energy : analyses from CORDEX-AFRICA climate experiments

The development of renewable electricity in Africa could be massive in coming decades, as a response to the rapid rising electricity demand while complying with the Paris Agreements. This study shows that in the high-resolution climate experiments of CORDEX-AFRICA, the annual mean solar potential is expected to decrease on average by 4% over most of the continent by the end of the century, reaching up to 6% over the Horn of Africa, as a direct result of decrease in solar radiation and increase in air surface temperature. These projections are associated with large uncertainties, in particular over the Sahel and the elevated terrains of eastern Africa. While the expected decrease may affect the sizing of the numerous solar projects planned in Africa for the next decades, this study suggests that it does not endanger their viability. At last, this study indicates that the design of such projects also needs to account for the non-negligible uncertainties associated with the resource

Assessing uncertainties in the regional projections of precipitation in CORDEX-AFRICA

International audienceOver the past decades, large variations of precipitation were observed in Africa, which often led to dramatic consequences for local society and economy. To avoid such disasters in the future, it is crucial to better anticipate the expected changes, especially in the current context of climate change and population growth. To this date, however, projections of precipitation over Africa are still associated with very large uncertainties. To better understand how this uncertainty can be reduced, this study uses an advanced Bayesian analysis of variance (ANOVA) method to characterize, for the first time in the regional climate projections of CORDEX-AFRICA, the different sources of uncertainty associated with the projections of precipitation over Africa.By 2090, the ensemble mean precipitation is projected to increase over the Horn of Africa from September to May and over the eastern Sahel and Guinea Coast from June to November. It is projected to decrease over the northern coast and southern Africa all year long, over western Sahel from March to August, and over the Sahel and Guinea Coast from March to May. Most of these projections however are not robust, i.e., the magnitude of change is smaller than the associated uncertainty. Over time, the relative contribution of internal variability (excluding interannual variability) to total uncertainty is moderate and quickly falls below 10%. By 2090, it is found that over the Horn of Africa, northern coast, southern Africa, and Sahel, most of the uncertainty results from a large dispersion across the driving Global Climate Models (in particular MIROC, CSIRO, CCCma, and IPSL), whereas over the tropics and parts of eastern Africa, most of the uncertainty results from a large dispersion across Regional Climate Models (in particular CLMcom)