http://197.159.135.214/jspui/handle/123456789/978 Wed, 24 Jun 2026 14:43:05 GMT 2026-06-24T14:43:05Z http://197.159.135.214/jspui/handle/123456789/1249 Title: Modelling the Impact of Coastal Urbanization on the West African Summer Monsoon Climate Authors: Faye, Aissatou Abstract: A lot of research has been done to understand and improve the relationship between land use and land cover modification vis-a-vis their interaction with the West African climate variability and climate change. However, the urbanization influence on the West African climate is not yet an elaborately researched subject of studies. In this context, this thesis examines the impact of coastal urbanization on the West African summer climate, by using the Regional Climate Model version 4 (RegCM4) coupled with the Community Land Surface Model version 4.5 (CLM4.5). A series of experiments were performed, in the present-day climate (1984-2005) and the RCP8.5 far future (2079- 2100), at 25 Km of horizontal resolution over the West African domain. Two types of simulations were performed with and without modification of the natural vegetation land cover with the urban parameterization (CLMU). Results from the model evaluation show the good performance of RegCM4 to simulate the main climatic variables and atmospheric circulation over West Africa during the June-September (JJAS) summer months. Arguably, RegCM4 reproduces well the spatio-temporal pattern of rainfall and temperature over West Africa in comparison with observations datasets. Again, the model’s capability to reproduce the West African atmospheric circulation drives and atmospheric variables compared to reanalyses was examined. RegCM4 gives a good representation of atmospheric circulation from the lower to the upper troposphere. The projected changes in West African climate under RCP8.5 and both RCP8.5 and urbanization were evaluated. For all the simulations, a significant warming is expected over the whole West Africa and will be more pronounced in the Sahel-Sahara at the end of the 21st century. A significant increase in temperature is also expected along the West African coastal region which corresponded to the ‘perturbed’ region. In the precipitation simulations, all the different simulations projected drier conditions in visually the entire West African region. However, the expected change is less significant in the combined urban expansion and RCP8.5 simulations. Evaluation of contribution due to urbanization alone shows that the change in the land cover gave a response of an average increase in temperature of approximately 3ºC over the urbanized region. The results imply that urban effects can reach the same magnitude as global warming. This warming could be a result of the urban heat island processes. Precipitation in the urbanized region and their sub-urban regions shows an increase of at least ~10%. This means that urbanization has both local and regional effects on the precipitation in West Africa. Furthermore, the results show that the characteristics of some atmospheric circulation such as AEJ and AEWs would change in the future climate. For example, a southward displacement of the AEJ position was observed which can explain the projected drier conditions in the region, especially in the Sahel part. Moreover, it should be noted that urbanization influences the atmospheric circulation drivers through the AEJ and AEWs. More convective activities are found under urban conditions and the sensitivity of the AWEs to the land surface conditions is noticed. Description: A Thesis submitted to the West African Science Service Centre on Climate Change and Adapted Land Use and the Federal University of Technology, Akure, Nigeria, in partial fulfillment of the requirements for the degree of Doctor of Philosophy Degree in West African Climate Systems Tue, 01 Oct 2019 00:00:00 GMT http://197.159.135.214/jspui/handle/123456789/1249 2019-10-01T00:00:00Z http://197.159.135.214/jspui/handle/123456789/1248 Title: Evaluation of Weather Research and Forecasting Model Physics in Simulating West African Monsoon Authors: Gbode, Imole Ezekiel Abstract: This research evaluates the ability of Weather Research and Forecasting model physics in simulating the West African monsoon. The purpose is to identify a possible model physics combinations in the WRF model whose outputs can be used to inform weather- and climate-related decision-making process at local to regional scale. In the study, the sensitivity of West African Monsoon (WAM) regimes to three model physics (i.e. Cumulus (CU), Microphysics (MP) and Planetary Boundary Layer (PBL) parameterization schemes) is assessed, performance of the model in representing the WAM dynamics is evaluated and impact of warming climate on WAM under the RCP8.5 scenario is also assessed. Twenty-seven (27) WRF simulations of the August-September 2007 monsoon regime at a 20-km grid over West Africa were evaluated to investigate the sensitivity of the WAM regime to the three model physics. The focus was on precipitation and surface temperature during the simulated period. The model’s precipitation was evaluated against the TRMM (reference), CMORPH and GPCP satellite rainfall products. Also, the surface temperature was evaluated against the ERA-Interim (reference), NCEP, MERRA, and GSAT. Results showed that all model physics combinations simulated the diurnal cycles of surface temperature better than the simulation of precipitation. A comparative model skill score was developed and used to identify that combination of WSM5-MYNN-nTDK and GD-MYJ-BMJ are best performing physics combinations in both temperature and precipitation. Also, the three WRF model physics combinations reproduced the characteristics of the region’s monsoon during selected normal (2007), wet (2008 and 2010) and dry (2001 and 2011) years. The dynamics of WAM such as monsoon flow, African Easterly Jet, and Tropical Easterly Jet, are replicated by most of the model combinations. Therefore, underscoring the strong potential impact of regional moisture, heat and momentum transport and redistribution on the monsoon dynamics as prescribed by the physics. Lastly, the Pseudo-Global Warming (PGW) simulation method perturbed by CESM1.0-CAM5.2 is employed to assess the impact of warming on WAM, the result shows a slight increase in precipitation amount (-2 to 16%) in the 2070s when compared with the current (reference) climate. This change is expected to be more pronounced in the Sahel, where the value is 16%, and less than 3% in the Guinea Coast. Furthermore, there is a decrease (increase) in both light and moderate (heavy) rainfall days. The outcomes of this research underscore the significance of WRF model as a potentially useful tool to investigate how future WAM seasons could vary in a changing climate. This provides relevant information to improve the understanding of the possible implications of such changes on economic activities such as agriculture, water resources, and other climate-related sectors, and to guide the design and implementation of climateresilient projects. Description: A Thesis submitted to the West African Science Service Centre on Climate Change and Adapted Land Use and the Federal University of Technology, Akure, Nigeria, in partial fulfillment of the requirements for the degree of Doctor of Philosophy Degree in West African Climate Systems Sun, 01 Sep 2019 00:00:00 GMT http://197.159.135.214/jspui/handle/123456789/1248 2019-09-01T00:00:00Z http://197.159.135.214/jspui/handle/123456789/1247 Title: Simulating the Effects of Land Use Land Cover Change on Hydrometeorological Parameters over West Africa Authors: Achugbu, Ifeanyi Chukwudi Abstract: Land Use Land Cover (LULC) in Sub-Sahara Africa has undergone rapid transformation in the last century. So comprehending the impact of land use land cover change and its interaction with the atmosphere by means of modeling, and its impact on some hydrometeorological variables is an interesting area both for present and future research. The land use land cover change (LULCC) over West Africa was analysed using the Moderate Resolution Imaging Spectroradiomater (MODIS) MCD12Q1 land use land cover data. The Weather Research and Forecasting (WRF) model was used to examine the effect of Land Surface Model (LSM) options of WRF model on temperature, precipitation and dew point temperature (DPT) in West Africa (WA). Eight simulations were performed using the Noah, Noah-multi-physics (Noah-MP), Community Land Model version 4 (CLM4) and Noah-MP LSM with a ground water option, all with same and other physics combinations. In order to assess the impacts of LULCC on some hydrometeorological parameters over WA, series of WRF simulations were carried out with 2001 and 2016 land use data, and 6 LULC scenarios which includes Built-up (Bu), Partial Deforest I (PDI), Partial Deforest II (PDII), Partial Afforest (PA), Total Afforest (TA) and Total Deforest (TD) were generated. The WRF-hydrological (WRF-Hydro) model was used to simulate the LULC change impact on streamflow over Sokoto Rima River Basin (SRRB) and 3 Forecast Points (FP) (Sokoto, Goronyo and Bakolori) were analysed. Analysis of the LULCC over West Africa (WA) between 2001 and 2016 revealed that there was a general decrease in all forest parameters and a steady increase in built up lands over the period of study. Results show that the LSMs performed differently for different variables in different land-surface conditions. However, Noah-MP was the viii overall best performing LSM for all the variables in all season, while Noah performed least. The differences in the simulations could be attributed to the differences in vegetation representation, soil column depth, number of soil layers and other processes in the LSMs. Experiment with 2001 and 2016 land use data revealed that WRF model is sensitive to changes in the land cover parameters. The integration of updated MODIS land use data into WRF model showed improvement in its outputs. Result also shows that for the entire area (10W, 10E, 5N, 15N), Bu scenario decreased DPT, evapotranspiration (ET) and precipitation, but increased 2m temperatures (T2m) and Sensible heat (SH). PDII and PDI scenario increased DPT, T2m, and decreases SH, ET, and Pr, while PA scenario slightly increases DPT, ET, Pr, SH and caused a decrease in T2m. TA scenario increased DPT, ET, Pr, but decreased T2m, and SH while TD decreased DPT, ET, but increases T2m, SH, and Pr. For all the FPs in the SRRB, Bu scenario caused the highest increase in streamflow, while TA scenario shows the highest decrease. The deforestation scenario generally led to an increase in streamflow, while the afforestation scenario led to a decrease. Higher streamflow occurs as a result of increased agricultural lands and decreased forest areas within the basin. The study has shown that land cover has changed over the years, and that the adverse effects of LULCC to the extreme will be increased temperature and discomfort as well as flooding as streamflow increases. The combination of Remote Sensing, GIS, WRF and WRF-hydro model provides a useful technique in assessing the impact of LULC on catchment hydrology. This is essential in selecting and developing feasible catchment management options that will promote sustainable utilization of land and water resources. Description: A Thesis submitted to the West African Science Service Centre on Climate Change and Adapted Land Use and the Federal University of Technology, Akure, Nigeria, in partial fulfillment of the requirements for the degree of Doctor of Philosophy Degree in West African Climate Systems Sat, 01 Feb 2020 00:00:00 GMT http://197.159.135.214/jspui/handle/123456789/1247 2020-02-01T00:00:00Z http://197.159.135.214/jspui/handle/123456789/1226 Title: Influence of the Quasi-Biennial Oscillation on Rainfall Producing Systems over West Africa Authors: Ballo, Abdoulaye Abstract: Rainfall is a major ingredient for economic development for most West African countries. It has serious implications on the socio-economic activities because more than 95% of its agricultural activities are rainfed and rain-fed agriculture serves as the main source of income for most of the economies. Therefore, rainfall variability in terms of amount and time can lead to good or poor agricultural production as either too much rainfall causes floods and water logging or very little rainfall results in inappropriate agricultural planning and activities. This study used ERA-Interim reanalysis and observational GPCP v2.2 to investigate the seasonal rainfall variability and relationship with the tropospheric jets. This work focuses on the Influence of the Quasi-biennial Oscillation on Rainfall Producing Systems over West Africa. This study analyses the relationship of the sub-tropical westerly jet (STJ) with the West African monsoon and its associated tropospheric jets. The association and relative influence of the low-level West African Westerly Jet (WAWJ), the AEJ and TEJ during wet and dry situation were also examined. Results showed that the sudden appearance of the TEJ in June and the intensification of the AEJ are linked to the weakening and disappearance of the stratospheric easterly flow (QBO) and the fast poleward retreat of the STJ. A close association between the northward movements of the AEJ core and rainfall belt was found. However, no clear relationship was seen between the northward advance of the rainfall distribution and the TEJ slow movement, as this jet core always lags the rainfall maximum. By considering rainfall variability causes, results also showed that the Sub-tropical jet (STJ) retreated poleward faster while the TEJ, WAWJ and ascending motion were all stronger, resulting in higher rainfall during wet years than dry. Furthermore, it was found that the so-called monsoon jump and the reversal of the shape of the monsoon layer both occur in May/June and that this may be linked to the weakening of the QBO and the sudden poleward retreat of the sub-tropical jet in the same months. The influence of stratospheric quasi-biennial oscillation (QBO) on the African Easterly Jet, Tropical Easterly Jet and West African precipitation was investigated through simulations using the Global Climate Model (GCM) using the Coupled Models Intercomparison Project Phase 5 (CMIP5). The performance of the CMIP5 models in reproducing the quasi-biennial oscillation was evaluated while the influence of the QBO on West African rainfall precipitation was studied using wavelet analysis over each zone of region (Sahel, Savannah, Guinea). Also, the composite of the effect during QBO and non-QBO years as well as of the QBO phases on rainfall variability were studied. The results show that all the models capture the general structure of the QBO but with some biases while HadGEM2-CC produced results closer to observation (ERAINT). It was also found that there is good coupling between QBO and precipitation over all zones of West Africa. The wavelet coherence analysis gives confirmation of the results. From this study it is concluded that the quasi-biennial oscillation has an important influence on West Africa precipitation that could lead to improved rainfall prediction over West Africa. Description: A Thesis submitted to the West African Science Service Center on Climate Change and Adapted Land Use and Université Joseph KI-ZERBO, Burkina Faso in partial fulfillment of the requirements for the Master of Science Degree in Informatics for Climate Change Sun, 01 Sep 2019 00:00:00 GMT http://197.159.135.214/jspui/handle/123456789/1226 2019-09-01T00:00:00Z