An Overview of Soil Survey and Classification as a Source of Secondary Information

The extraction of information from surveyed and classified soil maps by desired end-users has increased in recent times due to the high cost involved in the classification and mapping out of such soils by the individual users, and is also a time consuming process. In some instances, the end users do not even understand the methods that were used in producing the maps, the errors associated with it and the potential limitations of usage.  Knowledge over the years has shown that estimates contained in some soil maps are not perfect because they are typically based on limited data and limited information. To acknowledge that soil maps are not free of errors, the uncertainty in the estimates may be represented with error bounds that characterize the accuracy of the map. In recent times more advanced methods have been introduced with high precision of accuracy, including the use of artificial neural networks, remote sensing and photogrammetric procedures, combined with geographic information system (GIS). However, research has shown that, traditional soil survey persists as the most popular form of soil mapping and inventory. The need therefore arises to integrate and update rather than ignore the traditional soil survey techniques in favour of modern interpolation techniques. Keywords: survey, classification, soil maps, secondary information, desired use

Relationship between Rainfall-Runoff on the White Volta River at Pwalugu of the Volta Basin in Ghana

Rainfall and runoff patterns affect mans activities in so many ways and as such, designs of agricultural, storm water management, telecommunication, erosion, droughts, food security etc.  It is essential that the role of rainfall and stream flow are recognized, understood and taken into account when modelling hydrological processes within any Basin. The Pwalugu  catchment in the White Volta Basin experiences one rainy season which usually begins from April and peaks up in July, August, and September and gradually end with some showers in October and part of November. The basis of the analysis comprises of the rainfall events and runoff of the White Volta River at Pwalugu, to determine the relationship between the rainfall events and runoff and also estimates the contribution of rainfall to runoff by a certain threshold of rainfall. The analysis shows that the period is characterized by high inter-seasonal rainfall and discharge variability with a correlation coefficient of 0.78 which showed a strong positive relationship between rainfall and runoff in the catchment. For the linear regression relationships of cumulated rainfall events and discharges for the various years considered for the study, it is realized that 2003 and 2009 recorded the highest coefficients of correlation of 0.96 and 0.92 respectively. The studies showed that the minimum rainfall that can cause runoff in the catchment is 25mm which was set as a threshold. It is also observed from the analysis that a rainfall of at least 18mm can contribute 0.2m3/s of water to river flow with a correlation coefficient of 0.90 indicating a strong relationship between rainfall and riverflow. Keywords:Rainfall, Runoff, Volta Basin, Intensity, Threshol

Global horizontal irradiance in West Africa: evaluation of the WRF-solar model in convection-permitting mode with ground measurements

The number of solar power plants has increased in West Africa in recent years. Reliable reanalysis data and short-term forecasting of solar irradiance from numerical weather prediction models could provide an economic advantage for the planning and operation of solar power plants, especially in data-poor regions such as West Africa. This study presents a detailed assessment of different shortwave (SW) radiation schemes from the Weather Research and Forecasting (WRF) Model option Solar (WRF-Solar), with appropriate configurations for different atmospheric conditions in Ghana and the southern part of Burkina Faso. We applied two 1-way nested domains (D1 = 15 km and D2 = 3 km) to investigate four different SW schemes, namely, the Community Atmosphere Model, Dudhia, RRTMG, Goddard, and RRTMG without aerosol and with aerosol inputs (RRTMG_AERO). The simulation results were validated using hourly measurements from different automatic weather stations established in the study region in recent years. The results show that the RRTMG_AERO_D01 generally outperforms the other SW radiation schemes to simulate global horizontal irradiance under all-sky condition [RMSE = 235 W m−2 (19%); MAE = 172 W m−2 (14%)] and also under cloudy skies. Moreover, RRTMG_AERO_D01 shows the best performance on a seasonal scale. Both the RRTMG_AERO and Dudhia experiments indicate a good performance under clear skies. However, the sensitivity study of different SW radiation schemes in the WRF-Solar model suggests that RRTMG_AERO gives better results. Therefore, it is recommended that it be used for solar irradiance forecasts over Ghana and the southern part of Burkina Faso

Hourly global horizontal irradiance over West Africa: A case study of one-year satellite- and reanalysis-derived estimates vs. in situ measurements

Estimates of global horizontal irradiance (GHI) from reanalysis and satellite-based data are the most important information for the design and monitoring of PV systems in Africa, but their quality is unknown due to the lack of in situ measurements. In this study, we evaluate the performance of hourly GHI from state-of-the-art reanalysis and satellite-based products (ERA5, MERRA-2, CAMS, and SARAH-2) with 37 quality-controlled in situ measurements from novel meteorological networks established in Burkina Faso and Ghana under different weather conditions for the year 2020. The effects of clouds and aerosols are also considered in the analysis by using common performance measures for the main quality attributes and a new overall performance value for the joint assessment. The results show that satellite data performs better than reanalysis data under different atmospheric conditions. Nevertheless, both data sources exhibit significant bias of more than 150 W/m2 in terms of RMSE under cloudy skies compared to clear skies. The new measure of overall performance clearly shows that the hourly GHI derived from CAMS and SARAH-2 could serve as viable alternative data for assessing solar energy in the different climatic zones of West Africa

Evaluation of the WRF-solar model for 72-hour ahead forecasts of global horizontal irradiance in West Africa: A case study for Ghana

Accurate global horizontal irradiance (GHI) forecasting is critical for integrating solar energy into the power grid and operating solar power plants. The Weather Research and Forecasting model with its solar radiation extension (WRF-Solar) has been used to forecast solar irradiance in different regions around the world. However, the application of the WRF-Solar model to the prediction of GHI in West Africa, particularly Ghana, has not yet been investigated. The aim of this study is to evaluate the performance of the WRF-Solar model for predicting GHI in Ghana, focusing on three automatic weather stations (Akwatia, Kumasi and Kologo) for the year 2021. We used two one-way nested domains (D1 = 15 km and D2 = 3 km) to investigate the ability of the fully coupled WRF-Solar model to forecast GHI up to 72-hour ahead under different atmospheric conditions. The initial and lateral boundary conditions were taken from the ECMWF high-resolution operational forecasts. Our findings reveal that the WRF-Solar model performs better under clear skies than cloudy skies. Under clear skies, Kologo performed best in predicting 72-hour GHI, with a first day nRMSE of 9.62 %. However, forecasting GHI under cloudy skies at all three sites had significant uncertainties. Additionally, WRF-Solar model is able to reproduce the observed GHI diurnal cycle under high AOD conditions in most of the selected days. This study enhances the understanding of the WRF-Solar model’s capabilities and limitations for GHI forecasting in West Africa, particularly in Ghana. The findings provide valuable information for stakeholders involved in solar energy generation and grid integration towards optimized management in the region

Hourly global horizontal irradiance over West Africa: A case study of one-year satellite- and reanalysis-derived estimates vs. in situ measurements

Estimates of global horizontal irradiance (GHI) from reanalysis and satellite-based data are the most important information for the design and monitoring of PV systems in Africa, but their quality is unknown due to the lack of in situ measurements. In this study, we evaluate the performance of hourly GHI from state-of-the-art reanalysis and satellite-based products (ERA5, CAMS, MERRA-2, and SARAH-2) with 37 quality-controlled in situ measurements from novel meteorological networks established in Burkina Faso and Ghana under different weather conditions for the year 2020. The effects of clouds and aerosols are also considered in the analysis by using common performance measures for the main quality attributes and a new overall performance value for the joint assessment. The results show that satellite data performs better than reanalysis data under different atmospheric conditions. Nevertheless, both data sources exhibit significant bias of more than 150 W/m2 in terms of RMSE under cloudy skies compared to clear skies. The new measure of overall performance clearly shows that the hourly GHI derived from CAMS and SARAH-2 could serve as viable alternative data for assessing solar energy in the different climatic zones of West Africa

Effects of customized climate services on land and labor productivity in Burkina Faso and Ghana

International audienc

The impact of rain events on CO2 emissions from contrasting land use systems in semi-arid West African savannas

In the future the Sudanian savanna - one of West Africa's high-potential bread baskets - will likely face shorter rainy seasons with more extreme rains and droughts. That could have serious impacts on the vegetation and its carbon dioxide (CO2) exchange with potentially increasing CO2 emissions accelerating climate warming. Understanding how the CO2 fluxes in this area respond to environmental variables, in particular rain events, is essential, but available data are scarce. In this study, we monitored net ecosystem exchange (NEE) of CO2, rainfall and other environmental parameters during four years at three savannas. Savannas were characterized by different vegetation due to different land use: i) woody and nearly pristine, ii) mixture of cropland and grassland and iii) intensive grazing. The impact of rain events on CO2 exchange for these contrasting ecosystems were analyzed for single rain events (short-term) and on a yearly time scale (long-term) using three eddy covariance towers. We found that the woody pristine savanna site was a prominent sink of CO2 (-864 to -1299 g CO2 m(-2) y(-1)) while the degraded sites were net CO2 sources (118 to 605 g CO2 m(-2) y(-1)) with a complicated relation with annual rainfall amounts. The NEE responses to single rain events revealed that daytime rain systematically decreased the sink strengths at all sites, which might be associated with decreased light availability. At the degraded sites, additional factors increasing CO2 losses were rain duration and dry spell length. The observed patterns of immediate CO2 flux responses to rainfall at differently used savannas indicate strong internal feed-backs between vegetation and land use changes and raise the question whether the CO2 sink strengths might be overestimated with possible implications for global CO2 budgets. Sustainable adaptation strategies need to be developed for West Africa. (C) 2018 Elsevier B.V. All rights reserved