Abstract. A ground-based field campaign was conducted in southern West Africa from mid-June to the end of July 2016 within the framework of the Dynamics–Aerosol–Chemistry–Cloud Interactions in West Africa (DACCIWA) project. It aimed to provide a high-quality comprehensive data set for process studies, in particular of interactions between low-level clouds (LLCs) and boundary-layer conditions. In this region missing observations are still a major issue. During the campaign, extensive remote sensing and in situ measurements were conducted at three supersites: Kumasi (Ghana), Savè (Benin) and Ile-Ife (Nigeria). Daily radiosoundings were performed at 06:00 UTC, and 15 intensive observation periods (IOPs) were performed during which additional radiosondes were launched, and remotely piloted aerial systems were operated. Extended stratiform LLCs form frequently in southern West Africa during the nighttime and persist long into the following day. They affect the radiation budget and hence the evolution of the atmospheric boundary layer and regional climate. The relevant parameters and processes governing the formation and dissolution of the LLCs are still not fully understood. This paper gives an overview of the diurnal cycles of the energy-balance components, near-surface temperature, humidity, wind speed and direction as well as of the conditions (LLCs, low-level jet) in the boundary layer at the supersites and relates them to synoptic-scale conditions (monsoon layer, harmattan layer, African easterly jet, tropospheric stratification) in the DACCIWA operational area. The characteristics of LLCs vary considerably from day to day, including a few almost cloud-free nights. During cloudy nights we found large differences in the LLCs' formation and dissolution times as well as in the cloud-base height. The differences exist at individual sites and also between the sites. The synoptic conditions are characterized by a monsoon layer with south-westerly winds, on average about 1.9 km deep, and easterly winds above; the depth and strength of the monsoon flow show great day-to-day variability. Within the monsoon layer, a nocturnal low-level jet forms in approximately the same layer as the LLC. Its strength and duration is highly variable from night to night. This unique data set will allow us to test some new hypotheses about the processes involved in the development of LLCs and their interaction with the boundary layer and can also be used for model evaluation.

RESUMENSe presentan datos de radiación neta en todas las longitudes de onda promediados cada hora, registrados en una estación meteorológica situada en el campus de la Universidad Obafemi Awolowo, Ile-Ife (7.52º N, 4.52º E), Nigeria, durante un periodo completo de tres años (2010)(2011)(2012), para estudiar sus variaciones diurnas y estacionales. Esta información, obtenida con un radiómetro neto de alta sensibilidad de cuatro componentes, representa hasta hoy la información más consistente y detallada disponible para una localidad tropical de África Occidental. De acuerdo con los datos obtenidos, la radiación neta máxima ocurrió a las 14:00 LT (GMT + 1), y sus valores se incrementaron de manera considerable de 337.6 ± 146.4 Wm -2 en julio, que es el pico de la estación lluviosa, a 441.7 ± 82.4 Wm -2 durante marzo, en el final de la estación seca. En los meses de abril y octubre, que marcan el principio y fin de la estación lluviosa en Ile-Ife, se han registrado los valores más altos de radiación neta: 584.7 y 612.2 Wm -2 , respectivamente. Se observó una importante variación inter e intraestacional en los valores medios mensuales de radiación neta, debida principalmente a fluctuaciones de nubosidad y humedad. En el área de estudio, los datos revelaron la presencia de calentamiento radiativo neto en la superficie, cuya tendencia anual sigue una distribución bimodal. Los datos de este estudio respaldan los aportados por otros autores. ABSTRACTHourly averaged net all-wave radiation data spanning a complete three-year period (2010-2012) at a meteorological station located inside the Obafemi Awolowo University campus in Ile-Ife (7.52º N, 4.52º E), Nigeria is presented in this study to investigate its diurnal and seasonal variations. Using a high-sensitivity four-component net radiometer, the data represents so far the most consistent and detailed information available for a tropical location in West Africa. From the dataset, hourly maxima of the net radiation occurred at 14:00 LT (GMT + 1), whose values increased considerably from 337.6 ± 146.4 Wm -2 in July, which is the peak of the wet season, to 441.7 ± 82.4 Wm -2 in March, the end of the dry season. April and October, both of which mark the beginning and end of the raining season at Ile-Ife have recorded the highest values of 584.7 and 612.2 Wm -2 , respectively. There was strong intra/inter-seasonal variation observed in the monthly mean values of the net radiation due mainly to the fluctuations in cloudiness and humidity. In the study area, the data indicated a net radiative heating taking place at the surface, whose annual trend follows a bimodal distribution. The present data supports the results published in earlier studies by other authors.

In this article, the heavy metals in soils for agricultural activities were analyzed statistically. Ten (10) soil samples were randomly taken across the agricultural zones in Odo-Oba, southwestern Nigeria. Ten (10) metals; namely: copper (Cu), lead (Pb), chromium (Cr), arsenic (As), zinc (Zn), cadmium (Cd), nickel (Ni), antimony (Sb), cobalt (Co) and vanadium (V) were determined and compared with the guideline values. When the values were compared with the international standard, none of the heavy metals in the study area exceeded the threshold limit. However, the maximum range of the samples showed that Cr and V exceeded the permissible limit which could be associated with ecological risk. The data can reveal the distributions of heavy metals in the agricultural topsoil of Odo-Oba, and can be used to estimate the risks associated with the consumption of crops grown on such soils.

Groundwater plays a fundamental role in human life. Despite its indispensable characteristics, it is unfortunate that groundwater is often associated with low yield. The expanding demand for water and the cost involved in drilling boreholes therefore require the application and the proper use of groundwater investigation techniques to locate high yielding aquifers. A geophysical investigation involving an electrical resistivity method using a Schlumberger electrode array was conducted around Aaba residential area, a basement terrain of southwestern Nigeria. Sixteen Vertical Electrical Sounding (VES) stations were applied across the study area using a maximum current electrode separation of 100 m. The geoelectrical imaging from this study revealed that the lithologies are divided into topsoil, lateritic soil, Sandy clay/clayey sand/clay/weathered rock and the bedrock. Subsurface geoelectrical maps (overburden thickness, weathered layer isothickness, weathered layer isoresistivity, bedrock relief, bedrock resistivity, and correlations from geoelectric sections) were used to generate information about the groundwater potential of the study area. It was inferred that the eastern (VESs 1, 2, 8, 10, and 11) and the southwestern (VESs 13 and 14) regions are associated with high groundwater yield. Boreholes can be drilled to an average depth of 22.0 m (72.6 ft) on these axes. The groundwater potential of the northern (VES 5), central (VES 9), and southern (VES 12) parts of the study area were inferred to be of medium potential. The borehole drilling along these axes can be extended to the depth of 30.0 m (99.0 ft), with medium groundwater yield. However, the northeastern (VES 3 and VES 4) and the western (VESs 6, 7, 15, and 16) zones are characterized by low groundwater potential. This present study has been able to detect the drillable zones and depths for optimum groundwater yield in a crystalline terrain of Aaba residential area, Akure using VES. The resistivity sounding is efficient in characterization of aquifers for groundwater exploration.

The data in this article contains statistical analysis of radioelement in Odo-Oba flood plain of crystalline bedrock, Southwestern Nigeria. The data were acquired along twenty-two traverses. The length of each traverse is a function of its accessibility in the study area. The traverses covered the area used for agricultural practices and the area where these farm products are being sold to either the retailers or the consumers. Descriptive and multivariate statistical analyses were used to explore the measured emitted gamma radiation in Odo-Oba flood plain. The dataset can provide insights into the risks involved in exposure to outdoor radiation in a commercial centre when the average outdoor gamma radiation levels are compared to the global threshold values from the regulatory bodies such as World Health Organization, National Research Council, United States Environmental Protection Agency, Federal Environmental Protection Agency, International Commission on Radiological Protection, the United Nations Scientific Committee on the Effects of Atomic Radiation, and Federal Radiation Protection Service among others.