Browsing by Author "Annor, Thompson"

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    Modeling the spatial distribution of Global Solar Radiation (GSR) over Ghana using the Angström-Prescott ˚ sunshine duration model
    (Scientific African, 2019-05-21) Asilevi, Prince Junior; Quansah, Emmanuel; Amekudzi, Leonard Kofitse; Annor, Thompson; Klutse, Nana Ama Browne
    Solar radiation is an important geological and meteorological parameter. In most developing countries, data is readily unavailable owing to lack of instrumentation and skilled personnel. In this study, Global solar radiation (GSR) over Ghana has been quantified using the Angström–Prescott ˚ sunshine model with sunshine duration data from 22 synoptic stations distributed across the country’s ecological zones. The simulated data was gridded at 10 km by 10 km, establishing the spatial distribution of solar radiation over the country. Comparison with satellite data showed good results with root mean square error (RMSE) values of 1–5 MJm−2day−1 and correlation coefficient of 60 - 66%. Meanwhile, the estimated total GSR over the country was found to be 412.82 MJm−2day−1. The savanna zone had the maximum estimated total monthly mean GSR for the year, with the highest value of 20.76 MJm−2day−1 in Navrongo. The forest zone had the minimum estimated total annual mean GSR, with the lowest radiation level in Oda (17.11 MJm−2day−1). A maximum and minimum mean clearness index of 0.59 and 0.48 respectively are estimated, implying that about 53% of solar radiation at the top of the atmosphere reaches the study area after attenuation. The satellite data has a total monthly mean horizontal Global Solar irradiance of 366.62 MJm−2day−1. The study shows that the region is a potential field to harness and optimize solar energy for the operation of photovoltaic systems and solar collectors for industrial and domestic applications.
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    Numerical simulation of surface energy and water balances over a semiarid grassland ecosystem in the West African Savanna
    (Advances in Meteorology, 2017) Quansah, Emmanuel; Katata, Genki; Mauder, Matthias; Annor, Thompson; Amekudzi, Leonard K.; Bliefernicht, Jan; Heinzeller, Dominikus; Balogun, Ahmed A.; Kunstmann, Harald
    To understand surface energy exchange processes over the semiarid regions in West Africa, numerical simulations of surface energy and water balances were carried out using a one-dimensional multilayer atmosphere-SOil-VEGetation (SOLVEG) model for selected days of the dry and rainy seasons over a savanna grassland ecosystem in Sumbrungu in the Upper East region of Ghana. Te measured Bowen ratio was used to partition the residual energy into the observed sensible heat flux (�) and latent heat flux (LE) in order to investigate the impact of the surface energy closure on model performance. Te results showed that the model overall reproduced the diurnal changes in the observed energy fluxes, especially the net radiation (Rn), compared to halfhourly eddy covariance flux measurements, for the study periods. Te performance measure in terms of the correlation coefcient (�), centred root mean square error (RMSE), and normalized standard deviation (�) between the simulated � and LE and their corresponding uncorrected observed values ranged between R = 0.63–0.99 and 0.83–0.94, RMSE = 0.88–1.25 and 0.88–1.92, and � = 0.95–2.23 and 0.13–2.82 for the dry and rainy periods respectively, indicating a moderate to good model performance. Te partitioning of � and LE by SOLVEG was generally in agreement with the observations during the dry period but showed clear discrepancies during the rainy period, particularly afer rainfall events. Further sensitivity tests over longer simulation periods (e.g., 1 year) are required to improve model performance and to investigate seasonal exchanges of surface energy fluxes over the West African Savanna ecosystems in more details.
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    Rainfall and temperature projections and the implications on streamflow and evapotranspiration in the near future at the Tano River Basin of Ghana
    (Elsevier, 2021) Larbi, Isaac; Nyamekye, Clement; Dotse, Sam-Quarcoo; Danso, Derrick K.; Annor, Thompson; Bessah, Enoch; Limantol, Andrew Manoba; Attah-Darkwa, Thomas; Kwawuvi, Daniel; Yomo, Mawulolo; 0000-0002-3679-854X
    Climate change is projected to negatively affect water security which is already a chal lenge in many areas of Ghana including the Tano river basin (TRB). This study assessed the projections of rainfall and temperature and its impact on streamflow and actual evap otranspiration (ET) in the TRB of Ghana for 2021-2050 relative to the period 1986-2015. The impact assessment focused on how climate change under Representative Concentra tion Pathways (RCP 4.5 and RCP8.5) based on an ensemble mean of two regional climate models (RCMs) would affect streamflow and ET using the Soil and Water Assessment Tool (SWAT) model. Trend analysis and quantification for the streamflow and ET were analyzed using the Mann-Kendall’s and Sen’s slope estimators. The results show that the mean annual rainfall of 1401.9 mm would increase slightly by 0.5 % with a decreasing trend (1.22mm/yr) under the RCP4.5 scenario, but would decrease by 3.2% with a decreasing trend (0.3m mm/yr) under the RCP8.5 scenario. The mean annual temperature showed an increase (2.1 °C and 2.6 °C) with a statistically significant increasing trend of 0.07 and 0.09 °C/yr under RCP 4.5 and RCP8.5 respectively. An increase in ET with a non-significant increasing trend at a rate of 0.74 and 1.07 mm/year under RCP4.5 and RCP8.5 scenarios respectively is also projected. The mean annual streamflow is projected to decrease, with the decrease been more pronounced under the RCP8.5 (37.5%) scenario compared to the RCP4.5 scenario (19.9%). In general, the outcome of this study presents a useful perspective