The WASCAL hydrometeorological observatory in the Sudan Savanna of Burkina Faso and Ghana

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 CO2. 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 CO2 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

Analysis of sky conditions using solar radiation data over a tropical station

Radiation data in Nigeria are very sparse because radiation is not routinely measured. The data used for this work are from the physics Department of Obafemi Awolowo University, lle-lfe which is one of the few stations that collect radiation data in Nigeria. The daily, global and diffuse radiation measurements have been used to characterize the atmosphere of lle-lfe (70 14` N, 40 35` E) during January to December 1994. The clearness index ky (=H/H0) which gives the percentage depletion by the sky of the incoming global radiation and the relative sunshine (s/s0) gives the measure of cloud in the atmosphere has been adopted for use in this study. Also investigated are the diffuse radiation Kdiff (=Hdiff/H) and the diffuse coefficient Kcoef (= Hdiff/H0) that mirror the effectiveness of the sky in the scattering of the incoming radiation. Results show an average Kt value of 0.57 for year 1994 with maximum clearness index occurring in June (Kt= 0.68) and minimum in Dec (Kt =0.42). This present study also shows that the relative sunshine s/s0 has its minimum in August which indicates reduced hours of sunshine and solar insolation during the monsoon month of August in the tropical Nigeria station. Keywords: Daily, global and diffuse radiation, clearness index, diffuse coefficient, relative sunshine [Global Jnl Pure & Appl. Sci. Vol.9(3) 2003: 387-392

Effect of Deficit Irrigation Levels on Yield and Water Productivity of Some Maize Varieties in a Semi-arid Environment

The aim of this research is to determine the appropriate irrigation scheduling under three different maize varieties in Northern Guinea Savanna agro ecological zone of Nigeria. The trial was conducted during the 2015 and 2016 dry seasons at the Institute for Agricultural Research (IAR) field in Samaru (Latitude 11.11° N and Longitude 7.38°E). The experiment was laid out as a split – plot design replicated three times. Planting dates and supplementary Irrigation levels were in the main plots while maize varieties formed the sub-plots with the planting dates at 10days interval starting from March and February respectively. Three levels of irrigation were imposed based on levels of cumulative pan evaporation (Epan ) values of 1.0 Epan  (EI1), 0.70 Epan  (EI2) and 0.40 Epan  (EI3). Results from the two trials, revealed more efficient utilization of soil moisture by crops irrigated with 70 CU irrigation regime (6.91 and 6.97 kg grain/mm water respectively for the two seasons) while the least efficient water use was recorded by the full CU treatment (6.63 and 6.93 kg grain/mm water respectively) with relatively higher grain yields of 14% and 20% more than the 70 CU and 40 CU regimes respectively in 2015. Similar trends were recorded in the case of cob weight, 100 seed weight, seed/cob, shelling percentage and harvest index. In 2016 season, the similar trend was observed indicating the highest grain weight (3348.0 kg/ha) recorded by the full irrigation treatment which was statistically higher than (2724.0 and 2072.0 kg/ha) respectively for the 0.70 and 0.40 CU regimes. The best performing variety in terms of efficient water use and relatively high yield was the medium maturing variety (V3)

SPATIO-TEMPORAL TREND OF VEGETATION COVER OVER ABUJA USING LANDSAT DATASETS

Vegetation cover has acted as a source of carbon sinks and air purifier for a long period of time especially in developed cities thereby affecting the global climate change. The study was conducted to spatially estimate the Normalized Difference Vegetative Index (NDVI) which is a vegetation indicator for a period of 28 epoch years for Abuja from 1987 to 2014. The positive signatures of NDVI decrease from 2009 to 2014. Statistical analysis of the observed data samples at 95% confidence interval revealed that the changes observed in Year 2009 contributed most to the changes that was occurred in Year 2014.The modeled NDVI values for the year 2014 based on the regression analysis of the previous three years shows a significant agreement between the simulated values for year 2014 and the observed values. In general, there has been fast transformation of the vegetation cover to other land uses. The study reveals vegetation cover had reduced more significantly. It is also worthy to know that the model generated in this research can be used to predict future changes and trends in the vegetation cover. This will provide policy makers with useful information for the proper planning and design of the city and other capital cities over West Africa

Análise da frequência anual das condições de céu em Botucatu, São Paulo Analysis of the annual frequency of the sky conditions in Botucatu, São Paulo

Este trabalho apresenta uma análise da frequência das condições de céu em Botucatu. A classificação das condições de céu foi feita com base no índice de claridade (K T), calculado a partir de uma base de dados de 10 anos de radiação global diária. Em Botucatu há, ao longo do ano, predominância de dias com condição de céu claro, em média 114 dias. Para a condição de céu nebuloso a frequência média é de 61 dias e, em referência às duas condições de céu intermediárias, a frequência de céu parcialmente nebuloso com dominância para o difuso, é de 94 dias e a com dominância para o claro é de 96 dias. Os principais fatores influentes sobre as condições de céu em Botucatu são as entradas de frentes frias e a formação da Zona de Convergência do Atlântico Sul, as quais respondem principalmente pela alteração da condição de céu claro para a de céu nebuloso ou para a de céu parcialmente nebuloso com dominância para o difuso. Os aerossóis resultantes das queimadas em lavouras de cana-de-açúcar respondem pela alteração da condição de céu claro para a de céu parcialmente nebuloso com dominância para o claro.<br>This paper presents an analysis of the frequency of the sky conditions in Botucatu. The classification of sky conditions was made based on the clearness index (K T), calculated from a database with 10 years of measured daily global solar radiation. Throughout the year in Botucatu, there is a predominance of days with clear sky condition, on average 114 days. For cloudy sky condition, the average frequency is 61 days. About the two intermediate sky conditions, the frequency of the sky partially cloudy with dominance for the diffuse is 94 days and the one with dominance for the clear is 96 days. The main influential factors on the sky conditions in Botucatu are the inputs of cold fronts and the formation of the South Atlantic Convergence Zone. They respond primarily by altering the sky condition of clear to cloudy or partially cloudy with dominance to diffuse. The aerosols resulting from burning in sugarcane fields respond by altering the sky condition from clear to partly cloudy with dominance for the clear