Sustainability of African weather and climate information can only be ensured by investing in improved scientific understanding, observational data, and model capability. These requirements must be ...underpinned by capacity development, knowledge management; and partnerships of co-production, communication and coordination.
This study investigates the variability of convective properties during West and Central African monsoon season at both intra-seasonal and seasonal time scales based on 16-year Tropical Rainfall ...Measurement Mission (TRMM) precipitation features (PFs). Three rainforests (west coast, dry, Nigeria–Cameroon), two savannahs (Nigeria, Central Africa and South Sudan (CASS)), Sudano–Sahel and Sahel were classified. Convective properties were grouped according to six intra-seasonal periods defined as pre_monsoon, active_mam, break_mam, active_jjas, break_jjas and post_monsoon. Comparison of West (rainforest zone: south of 12° N) and Central (savannah zone: south of 12° N) African mean convective properties showed that West African rainforest zones often have higher numbers of PFs and mean convective properties than the CASS savannah at all the intra-seasonal periods except during the post-monsoon period. The convective properties are more frequent during pre_monsoon, active_mam and break_mam periods than during the intra-seasonal periods of JJAS (June–September) in the West African rainforest zone, and thus indicating the two distinct rainfall seasons in rainforest of West Africa, but this was not observed in Central Africa. Convective properties are found to have similar climatological pattern to precipitation climatology during March through May (MAM) and JJAS. Extreme cases of flashcounts (> 275), depressed 85-GHz polarisation-corrected temperature (49–65 K and 65–85 K) and maximum heights (> 17.59 km) of the 30 dBZ are frequent in the Nigeria–Cameroon rainforest during MAM, but extreme system sizes (≥ 80,000 km
2
) are found to be located in the CASS savannah zone during JJAS.
Green liquor dreg (GLD) is a side stream generated by pulp industry. Due to its complex physicochemical nature, it has been reported to be difficult material to utilize. Here, a novel approach ...towards utilization of moist and dry green liquor dreg as binder and filler in alkali-activated lightweight artificial aggregates was developed. Dried GLD and moist GLD were granulated with blast furnace slag (BFS) and Bioash in different mixtures using alkali activation. The effect of the GLD nature (dried and moist) on strength, microstructure and durability of the lightweight granules were determined and compared. Results show that the method used in homogenizing the moist GLD and other powders was efficient and improved the frost resistance. The reaction product identified in the granule’s includes calcium silicate hydrate, Mg–Al layered double hydroxides, and ettringite. These results demonstrate the potential of GLD as a binder and fillers in cementitious applications.
•Green liquor dregs an industrial residue was upcycled in alkali-activated binder as artificial aggregates.•The texture of the GLD plays a significant role in the strength development and microstructural properties of the aggregates.•GLD in the synthesis improves the reactivity and act as filler in the aggregates.•The granules showed considerable resistance to frost.
Abstract
Floods as a result of severe storms cause significant impacts on lives and properties. Therefore, timely and accurate forecasts of the storms will reduce the associated risks. In this study, ...we look at the characteristics of a storm on 28 June, 2018 in Kumasi from a rain gauge network and satellite data, and reanalysis data. The storm claimed at least 8 lives and displaced 293 people in Kumasi, Ghana. The ability of satellite and reanalysis data to capture the temporal variations of the storm was assessed using a high temporal resolution (accumulation per minute) rain gauge data. We employed the observation data from the Dynamics–Aerosol–Chemistry–Cloud Interactions in West Africa (DACCIWA) rain gauges to assess the storm's onset, duration, and cessation. Subsequently, the performance of the ERA5 reanalysis and Global Precipitation Measurement (GPM) satellite precipitation estimates in capturing the rainfall is assessed. Both GPM and the ERA5 had difficulty reproducing the hourly pattern of the rain. However, the GPM produced variability that is similar to the observed. Generally, the region of maximum rainfall was located in the southern parts of the study domain in ERA5, while GPM placed it in the northern parts. The study contributes a verification measure to improve weather forecasting in Ghana as part of the objectives of the GCRF African Science for Weather Information and Forecasting Techniques (SWIFT) project.
Aluminosilicate glasses are materials with a wide range of technological applications. The field strength of network-modifying cations strongly influences the structure of aluminosilicate glasses and ...their suitability for various applications. In this work, we study the influence of the field strength of network-modifying cations on the structure of (Na2O)1–x(MgO)x(Al2O3)0.25(SiO2)1.25 glasses. Due to the higher cation field strength of magnesium than sodium, magnesium prefers the role of network modifier, while sodium preferentially acts as a charge compensator. When magnesium replaces sodium as network modifier, Q3 silicon species are converted into Q2 species. The replacement of sodium with magnesium as charge compensator leads to the following changes: (1) the proportion of aluminum-rich Q4 species Q4(4Al) and Q4(3Al) decreases, while the proportion of aluminum-deficient Q4 species Q4(2Al) and Q4(1Al) increases; and (2) there is an increased tendency for phase separation between silica-rich and alumina-rich glasses.
This research investigated the effects of Land Use Land Cover Change (LULCC) over the Sokoto Rima River Basin (SRRB) using a setup of Weather Research and Forecasting (WRF) atmospheric model to ...generate the parameters to force WRF hydrological (WRF-Hydro) model which comprises of a parent domain at 12km horizontal resolution with an updated MODIS Land Use (LU) data and the nested domain at 4km resolution which focuses on the SRRB. The calibration of the model was done by modifying the infiltration and the Manning's roughness parameters. WRF-Hydro model was used to run simulations with the control LU and five different LU scenarios generated for Urban (Ur), Grassland (Gr), Savanna (Sa), Forest (Fr) and Barren (Ba). For the period analysed, simulation with Gr scenario increased streamflow in all the forecast points, while the Sa decreases it. A strong correlation was noted between the input precipitation and streamflow for all LU scenarios, and a significant Specific Discharge to Rainfall (SDR) for Ur, Fr and Ba scenarios. There was an increase in streamflow in the dry period due to afforestation and a decrease due to deforestation. Areas where grasslands were converted into savanna showed a little increase in evapotranspiration ET. There was more ET for the Sa scenario than the Gr scenario in the wet period, while there was more ET in the dry period for Gr scenario than it is for the Sa scenario. The study has shown that ET is a major factor to changes in streamflow due to LU changes over the basin. The sensitivity of the model to LULCC is reasonable, but more research is recommended to compare results with different hydrological model popularly used for LULCC impact studies.
Weather research and forecasting (WRF) hydrological model; Land use land cover change (LULCC); Streamflow; Savanna; Grassland.
The aim of this study was the valorization of paper sludge waste from paper industry in designing one-part geopolymer cement using ground granulated blast furnace slag as main precursor. The effects ...of increasing the amount of paper sludge pretreated with a constant amount of sodium hydroxide (2% of slag) on mechanical strength, heat evolution, setting time and durability were analyzed. The reaction products were characterized using X-ray diffraction and thermogravimetric analysis. The findings showed that paper sludge can successfully be used as a secondary source of calcium carbonate in the one-part (“just add water”) geopolymer. The compressive strength of the cured geopolymer increased with increasing the amount of paper sludge, and the non-reacted sludge acted as a filler. The maximum strength (42 MPa, 28 d) was reached at 18 wt-% paper sludge addition. The main reaction products were calcium aluminate silicate hydrate and hydrotalcite-like cementitious gels. From the perspective of its blast-furnace slag content, strength properties, water absorption and setting time, the one-part geopolymer cement could be classified as a CEM IIIC and Type 32.5N class cement under the European standard EN-197.
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While conventional weather forecasts focus on meteorological thresholds for extreme events, Impact-Based Forecasts (IBF) integrate information about the potential severity of weather impacts with ...their likelihood of occurrence. As IBF provides an indication of local risk, there is an increasing uptake of this approach globally. Despite the vulnerability of West Africa to severe weather, and the potential benefits of such a risk-based approach for informing disaster risk reduction, IBF remains rarely used in this region. To meet this need, three national workshops were held in Ghana, Nigeria and Senegal with forecasters, project researchers and users of Climate Information Services (CIS) from key sectors (e.g., agriculture, water resources, disaster, risk reduction). In addition, a more localized district level workshop was held in Northern Ghana to explore needs at a subnational scale in Tamale District. The objectives of these workshops were to evaluate the current use of forecast products provided by National Meteorological and Hydrological Services (NMHSs) and to explore the potential for applying IBF. Findings indicate a recognition that the quality of forecast products provided by NMHSs in West Africa has substantially improved in recent years. However, challenges remain related to user understanding, clarity about forecast uncertainty, insufficient spatial and temporal resolution of forecasts leading to limited trust in forecasts. The workshops identified high demand for weather information related to storms, droughts and heatwaves in all the three countries. Dust storms were identified as having strong potential for IBF application in both Nigeria and Senegal. To increase the uptake of CIS by users in West Africa, NMHSs will need to develop and implement user-tailored IBF in their normal weather forecast approaches and improve communication channels with user communities. There is an urgent need for governments in West Africa to enhance the capacity of NMHSs to incorporate IBF as a routine forecast activity by first establishing a National Framework for Climate Services with user engagement as a key first pillar.
Drying shrinkage of alkali-activated binders are recognized as one of the most important properties towards quality assurance of the binders. In this study, results of experimental studies and ...predictive models developed to determine the drying shrinkage of alkali - activated blast furnace-fly ash mortars are presented and discussed. Different parameters were altered in the experimental study such as the content of GGBFS, FA, activator modulus (Ms), and curing temperature. Their effects on the drying shrinkage of the mortars were then evaluated. Artificial neural network (ANN) and Multiple Linear Regression (MLR) models were built to predict the drying shrinkage at 28 days using the above-mentioned parameters as inputs. The experimental results and ANN model predictions showed strong correlations. The prediction of 28-days drying shrinkage for the alkali-activated GGBFS-FA was more accurate using ANN than MLR.
Alkali-activated materials (AAMs) are alternative binders that can be used instead of Portland cement in construction. One of the main drivers in their utilization is that AAMs can be designed to ...have lower CO2 emissions using industrial residues. The main component of AAMs is aluminosilicate precursor, which is frequently waste based. However, the sustainable profile and cost-efficiency of AAMs are greatly affected by the selection of the alkali activator. Commonly used activators include bulk chemicals, such as sodium hydroxide or silicates, which have a relatively high carbon footprint and cost that can inhibit AAM applicability for large-scale construction applications. Consequently, several locally available, but underutilized, agricultural and industrial by-products or wastes have been investigated as alternative alkali activators. Globally, millions of tons of these residues are produced annually, and currently, they are mostly landfilled. Utilization of these residues as alternative alkali activators not only solves the residues-management issue, but also has noteworthy economic and environmental benefits. Utilization and properties of these waste-based activators in AAMs are comprehensively reviewed in this manuscript. Various studies showed the formation of alkali silicates from amorphous silica residues, alkali hydroxides, carbonates, and aluminates sourced from biomass and industrial residues. The resulting binder exhibited similar reactivity to commercial activators and considerable binder strength. However, the durability, shrinkage, and workability properties were not investigated in most of the reviewed studies.
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