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1.
Interannual variability of rainfall over the Sahel based on multiple regional climate models simulations 总被引：1，自引：0，他引：1
Ismaila Diallo Mouhamadou B. Sylla Moctar Camara Amadou T. Gaye 《Theoretical and Applied Climatology》2013,113(1-2):351-362
We analyse the interannual variability of the averaged summer monsoon rainfall over the Sahel from multiple regional climate models driven by the ERA-interim reanalysis and seek to provide effective information for future modelling work. We find that the majority of the models are able to reproduce the rainfall variability with correlation coefficient exceeding 0.5 compared with observations. This is due to a good representation of the dynamics of the main monsoon features of the West African climate such as the monsoon flux, African Easterly Jet (AEJ) and Tropical Easterly Jet (TEJ). Among the models, only HIRHAM fails to reproduce the rainfall variability exhibiting hence a correlation coefficient of ?0.2. This deficiency originates from the fact that HIRHAM does not properly capture the variability of monsoon flow and the relationship between rainfall and the AEJ dynamic. We conclude that a good performance of a regional climate model in simulating the monsoon dynamical features variability is of primary importance for a better representation of the interannual variability of rainfall over the Sahel. 相似文献
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Multiyear simulation of the African climate using a regional climate model (RegCM3) with the high resolution ERA-interim reanalysis 总被引：2，自引：2，他引：0
Mouhamadou Bamba Sylla E. Coppola L. Mariotti F. Giorgi P. M. Ruti A. Dell’Aquila X. Bi 《Climate Dynamics》2010,35(1):231-247
This study examines the ability of the latest version of the International Centre for Theoretical Physics (ICTP) regional
climate model (RegCM3) to reproduce seasonal mean climatologies, annual cycle and interannual variability over the entire
African continent and different climate subregions. The new European Center for Medium Range Weather Forecast (ECMWF) ERA-interim
reanalysis is used to provide initial and lateral boundary conditions for the RegCM3 simulation. Seasonal mean values of zonal
wind profile, temperature, precipitation and associated low level circulations are shown to be realistically simulated, although
the regional model still shows some deficiencies. The West Africa monsoon flow is somewhat overestimated and the Africa Easterly
Jet (AEJ) core intensity is underestimated. Despite these biases, there is a marked improvement in these simulated model variables
compared to previous applications of this model over Africa. The mean annual cycle of precipitation, including single and
multiple rainy seasons, is well captured over most African subregions, in some cases even improving the quality of the ERA-interim
reanalysis. Similarly, the observed precipitation interannual variability is well reproduced by the regional model over most
regions, mostly following, and sometimes improving, the quality of the ERA-interim reanalysis. It is assessed that the performance
of this model over the entire African domain is of sufficient quality for application to the study of climate change and climate
variability over the African continent. 相似文献
4.
High-resolution simulations of West African climate using regional climate model (RegCM3) with different lateral boundary conditions 总被引：3，自引：1，他引：2
M. B. Sylla A. T. Gaye J. S. Pal G. S. Jenkins X. Q. Bi 《Theoretical and Applied Climatology》2009,98(3-4):293-314
To downscale climate change scenarios, long-term regional climatologies employing global model forcing are needed for West Africa. As a first step, this work examines present-day integrations (1981–2000) with a regional climate model (RCM) over West Africa nested in both reanalysis data and output from a coupled atmospheric–ocean general circulation model (AOGCM). Precipitation and temperature from both simulations are compared to the Climate Research Unit observations. Their spatial distributions are shown to be realistic. Annual cycles are considerably correlated. Simulations are also evaluated with respect to the driving large-scale fields. RCM offers some improvements compared to the AOGCM driving field. Evaluation of seasonal precipitation biases reveals that RCM dry biases are highest on June–August around mountains. They are associated to cold biases in temperature which, in turn, are connected to wet biases in precipitation outside orographic zones. Biases brought through AOGCM forcing are relatively low. Despite these errors, the simulations produce encouraging results and show the ability of the AOGCM to drive the RCM for future projections. 相似文献
5.
Nowadays,the preservation of natural resources,the reuse,and the recycling of waste and by-products in the cement industry are gaining increasing attention in a sustainable development project.In this perspective,many studies focus on finding solutions in order to propose environmentally friendly materials.Nowadays the sediments represent a way to preserve the natural resources by their reuse as a secondary raw material in multiple applications(concrete,roads,landscaped mound,etc.).However,they commonly contain contaminants,organic matter(5%-30%),high water content(50%-200%),and relatively small particle size(Dmax≤300 mm).Therefore to improve the mechanical properties of this material as well as its physiochemical ones,specific methods of characterization and appropriate treatment techniques(calcination,chemical treatment,etc.)are required.This article presents a bibliographical review of the efficient use of sediments in cementitious matrix.It details experimental tests that must be performed to ensure the durability of sediment-based structure and assess their environmental impact under prescribed conditions. 相似文献
6.
Kazuharu Bamba Mubasher Jamil D. Momeni Ratbay Myrzakulov 《Astrophysics and Space Science》2013,344(1):259-267
We study the generalized second law (GSL) of thermodynamics in f(T) cosmology, where T is the torsion scalar in teleparallelism. We consider the universe as a closed bounded system filled with n component fluids in the thermal equilibrium with the cosmological boundary. We use two different cosmic horizons: the future event horizon and the apparent horizon. We show the conditions under which the GSL will be valid in specific scenarios of the quintessence and the phantom energy dominated eras. Further we associate two different entropies with the cosmological horizons: with a logarithmic correction term and a power-law correction term. We also find the conditions for the GSL to be satisfied or violated by imposing constraints on model parameters. 相似文献
7.
Formation of a Flare-Productive Active Region: Observation and Numerical Simulation of NOAA AR 11158
We present a comparison of the Solar Dynamics Observatory (SDO) analysis of NOAA Active Region (AR) 11158 and numerical simulations of flux-tube emergence, aiming to investigate the formation process of this flare-productive AR. First, we use SDO/Helioseismic and Magnetic Imager (HMI) magnetograms to investigate the photospheric evolution and Atmospheric Imaging Assembly (AIA) data to analyze the relevant coronal structures. Key features of this quadrupolar region are a long sheared polarity inversion line (PIL) in the central δ-sunspots and a coronal arcade above the PIL. We find that these features are responsible for the production of intense flares, including an X2.2-class event. Based on the observations, we then propose two possible models for the creation of AR 11158 and conduct flux-emergence simulations of the two cases to reproduce this AR. Case 1 is the emergence of a single flux tube, which is split into two in the convection zone and emerges at two locations, while Case 2 is the emergence of two isolated but neighboring tubes. We find that, in Case 1, a sheared PIL and a coronal arcade are created in the middle of the region, which agrees with the AR 11158 observation. However, Case 2 never builds a clear PIL, which deviates from the observation. Therefore, we conclude that the flare-productive AR 11158 is, between the two cases, more likely to be created from a single split emerging flux than from two independent flux bundles. 相似文献
8.
Projected increased risk of water deficit over major West African river basins under future climates
Mouhamadou Bamba Sylla Aissatou Faye Nana Ama Browne Klutse Kangbeni Dimobe 《Climatic change》2018,149(2):247-260
Despite decades of research, large multi-model uncertainty remains about the Earth’s equilibrium climate sensitivity to carbon dioxide forcing as inferred from state-of-the-art Earth system models (ESMs). Statistical treatments of multi-model uncertainties are often limited to simple ESM averaging approaches. Sometimes models are weighted by how well they reproduce historical climate observations. Here, we propose a novel approach to multi-model combination and uncertainty quantification. Rather than averaging a discrete set of models, our approach samples from a continuous distribution over a reduced space of simple model parameters. We fit the free parameters of a reduced-order climate model to the output of each member of the multi-model ensemble. The reduced-order parameter estimates are then combined using a hierarchical Bayesian statistical model. The result is a multi-model distribution of reduced-model parameters, including climate sensitivity. In effect, the multi-model uncertainty problem within an ensemble of ESMs is converted to a parametric uncertainty problem within a reduced model. The multi-model distribution can then be updated with observational data, combining two independent lines of evidence. We apply this approach to 24 model simulations of global surface temperature and net top-of-atmosphere radiation response to abrupt quadrupling of carbon dioxide, and four historical temperature data sets. Our reduced order model is a 2-layer energy balance model. We present probability distributions of climate sensitivity based on (1) the multi-model ensemble alone and (2) the multi-model ensemble and observations. 相似文献
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Talardia Gbangou Mouhamadou Bamba Sylla Onemayin David Jimoh Appollonia Aimiosino Okhimamhe 《Climatic change》2018,151(3-4):445-462
This paper examines changes in rainfall effectiveness indices of the Awun basin in Nigeria during the late twenty-first century for agricultural applications with outputs from high-resolution regional climate model (RCM) simulations. The RCM simulations are driven by two global climate models for a reference period (1985–2004) and a future period (2080–2099) and for RCP4.5 (a scenario with some mitigation) and RCP8.5 (a business as usual scenario) forcings. Simulations are provided for the control (1985–2004) and scenario (2080–2099) periods. Observations from synoptic station are used for bias-correction. Three indices being local onset date, seasonality index (SI), and hydrologic ratio (HR) are analyzed. Onset and HR are tested with two evapotranspiration (ETp) models. Farmers’ perceptions are also collected to validate trends of rainfall indices for the present-day climate. We found that onset dates do not depend much on the ETp models used, and farmers’ perceptions are consistent with predicted rainfall patterns. Present-day climate trend shows an early onset. However, onset is projected to be late in future and the delay will be magnified under the business as usual scenario. Indeed, average onset date is found on the 5th May for present-day while in the future, a delay about 4 and 8 weeks is projected under RCP4.5 and RCP8.5 scenarios respectively. SI is between 0.80 and 0.99, and HR is less than 0.75 for all scenarios, meaning respectively that (i) the rainy season will get shorter and (ii) the area will get drier in the future compared to the present-day. Local stakeholders are forewarned to prepare for potential response strategies. A continuous provision of forecast-based rainfall indices to support farmer’s decision making is also recommended. 相似文献
10.
David Baratoux Cheikh Ahmadou Bamba Niang Wolf Uwe Reimold Marian Selorm Sapah Mark Walter Jessell Daniel Boamah Gayane Faye Sylvain Bouley Olivier Vanderhaeghe 《Meteoritics & planetary science》2019,54(10):2541-2556
The about 10.5 km diameter Bosumtwi impact crater is one of the youngest large impact structures on Earth. The crater rim is readily noticed on topographic maps or in satellite imagery. It defines a circular basin filled by water (Lake Bosumtwi) and lacustrine sediments. The morphology of this impact structure is also characterized by a circular plateau extending beyond the rim and up to 9–10 km from the center of the crater (about 2 crater radii). This feature comprises a shallow ring depression, also described as an annular moat, and a subdued circular ridge at its outer edge. The origin of this outermost feature could so far not be elucidated based on remote sensing data only. Our approach combines detailed topographic analysis, including roughness mapping, with airborne radiometric surveys (mapping near‐surface K, Th, U concentrations) and field observations. This provides evidence that the moat and outer ring are features inherited from the impact event and represent the partially eroded ejecta layer of the Bosumtwi impact structure. The characteristics of the outer ridge indicate that ejecta emplacement was not purely ballistic but requires ejecta fluidization and surface flow. The setting of Bosumtwi ejecta can therefore be considered as a terrestrial analog for rampart craters, which are common on Mars and Venus, and also found on icy bodies of the outer solar system (e.g., Ganymede, Europa, Dione, Tethys, and Charon). Future studies at Bosumtwi may therefore help to elucidate the mechanism of formation of rampart craters. 相似文献