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Dataset consisting of hourly global and diffuse solar radiation measured over the period February 1992 and December 2002 have been utilized to investigate the diurnal and seasonal variations of hourly and daily clearness index together with the diffuse fraction at a tropical station Ile-Ife (7.5°N, 4.57°E), Nigeria. Statistical analysis (the frequency and cumulative frequency distribution of the hourly and daily clearness index) and subsequent characterization of the sky conditions over the station based on these were also done, and their implications for solar energy utilization in the area discussed.Daytime ( Statistical analysis of hourly and daily clearness index showed that the local sky conditions at the station were almost devoid of clear skies and overcast skies (clear skies and overcast skies occurred for only about 3.5% and 4.8% of the time respectively). The sky conditions were rather predominantly cloudy (cloudy skies occurred for about 88% of the time) all the year round.

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Watersheds with rich hydrometeorological equipment are still very limited in West Africa but are essential for an improved analysis of environmental changes and their impacts in this region. This study gives an overview of a novel hydrometeorological observatory that was established for two mesoscale watersheds in the Sudan Savanna of Southern Burkina Faso and Northern Ghana as part of the West African Science Service Centre on Climate Change and Adapted Land Use (WASCAL) program. The study area is characterized by severe land cover changes due to a strongly increasing demand of agricultural land. The observatory is designed for long-term measurements of >30 hydrometeorological variables in subhourly resolution and further variables such as CO 2 . This information is complemented by long-term daily measurements from national meteorological and hydrological networks, among several other datasets recently established for this region. A unique component of the observatory is a micrometeorological field experiment using eddy covariance stations implemented at three contrasting sites (near-natural, cropland, and degraded grassland) to assess the impact of land cover changes on water, energy, and CO 2 fluxes. The datasets of the observatory are needed by many modeling and field studies conducted in this region and are made available via the WASCAL database. Moreover, the observatory forms an excellent platform for future investigations and can be used as observational foundation for environmental observatories for an improved assessment of environmental changes and their socioeconomic impacts for the savanna regions of West Africa. drologically enhanced version of the Weather and Research Forecasting Model.West Africa is a region for which high-quality hydrometeorological measurements are very scarce (Jones et al., 2015). However, such information is needed for a better scientific understanding of hydrological processes and their interactions with the atmosphere and the biosphere. Observational data form the basis for the development of reliable modeling approaches for climate change analyses, as well as for determining the impact of land cover changes in hydrology and other disciplines. Many regions in West Africa are characterized by significant land cover changes due to a widespread conversion of savanna and other ecosystems into agricultural land (Ouedraogo et al., 2009;Knauer et al., 2017), which is expected to continue in the future. Land cover change analysis is the basis for the development of sustainable land management practices that strengthen the resilience of socioecological systems against climate extremes and enhance food security. Moreover, substantial biosphere-precipitation feedbacks have been detected for the West African Core Ideas • A new hydrometeorological observatory was established for the Sudan Savanna. • More than 30 hydrometeorological variables in subhourly resolution are provided. • Water, energy, and CO 2 fluxes are monitored along a land use change gradient. • The data form the basis for...