In this study, Climate Research Unit monthly observations were used to assess the trends of potential evapotranspiration (PET) over West Africa from 1906 to 2015. Trends and changes in PET during the 110-year study period and two reference climatological periods (1931-1960 and 1961-1990) were examined. Nonparametric trend test of the Mann-Kendall and Kolmogorov-Smirnov was employed to find the changes in trends of PET and their significance or otherwise. The contributions of some meteorological parameters (air temperatures, precipitation and cloud cover) to the observed trends in PET were also examined. Results of long-term data analysis showed mixed trends in PET in the three designated zones (Guinea, Savanna and Sahel) but notable significant increasing trends (0.165 mm per year) at p = 0.1 in Sahel. However, very sharp differences in PET were observed in both reference periods across the zones with significant decreasing trends (at p = 0.01) in PET during the first period but increasing significant trends (at p = 0.1) during the second. In spite of this pattern of variations, general reductions in PET (− 0.6% to − 1.2%) were observed, which were found to be triggered by decrease in temperature (− 0.13 to − 1.07%) and vapour pressure (− 0.02 to − 0.33%) as well as increase in cloudiness (0.01-0.05%). However, the magnitudes of changes in PET were found to be insignificant in all the zones. Maximum temperature, more than other dominant climatic parameters, contributed significantly (Theil-Sen's regression: 23.5% ≤ β ≤ 50.3%; p = 0.01) to observed variations in PET.

This study evaluates the performance of some evapotranspiration models at Ile – Ife (7o 33’ N, 4o 33’ E) Nigeria. This was to identify suitable evapotranspiration (ET) models at the study site and to provide useful information for standardizing evapotranspiration estimations at a tropical location. Meteorological parameters (wind speed, relative humidity, temperature, solar radiation, soil heat flux, and net radiation) were routinely measured at the Obafemi Awolowo University (OAU) Meteorological Station located within the Teaching and Research Farm of the campus for a period of a month (1st – 29th July 2014). Nine standardized models for the estimation of ET; Penman-Monteith (FAO-56 PM), Priestly-Taylor (PT), Makkink (MAKK), Jensen-Haise (JH), Hargreaves-Samani (HS), Ivanov (IVA), Modified Romanenko (MROM), FAO-24 Radiation (FAO-24 RAD) and Turc (TURC) models were employed. The ET values obtained from these models were then compared to the estimated values obtained from the FAO-56 PM equation recommended as the international standard method for determining reference ET. The estimation of the ET obtained from FAO – 56 PM model ranged between 0.426 – 2.239 mm/day, MAKK, JH, and HS gave estimation closest to this, ranging from 0.544 – 2.272 mm/day. The estimation of ET from other models revealed that PT has the highest value ranging between 1.323 – 6.936 mm/day, followed closely was FAO – 24 RAD with values ranging between 1.197 – 6.500 mm/day, values of IVA model ranged from 0.620 – 1.829 mm/day, MROM value ranged from 1.240 – 3.659 mm/day, TURC has the least value ranging from 0.190 – 0.584 mm/day. Using the result of the mean biased error and regression analysis, JH model compared best with the FAO – 56 PM with coefficient of determination (R2) = 0.927; slope (b) = 0.957; mean biased error (MBE) = 0.133, this was followed closely by HS with value R2 = 0.929; b = 1.199; MBE = - 0.075 and MAKK with the value R2 = 0.931; b = 1.198; MBE = - 0.052. However, the other models showed significant over or underestimation of the ET benchmark values. The performance of the other models showed no improvement after they were recalibrated by adjusting their original coefficients. Thus, six out of the ET models employed in this study [the Priestly-Taylor (PT), Makkink (MAKK), Jensen-Haise (JH), Hargreaves-Samani (HS), FAO-24 Radiation (FAO-24 RAD) and Turc (TURC)] were found suitable for the climatic region of Ile – Ife after the adjustment of their coefficients.

No abstract

No abstract

The present study determined the physicochemical parameters, saturation and unsaturation of twenty-four branded and unbranded vegetable oils sold in Sabo Market, Kaduna State by Fourier Transformed Infrared Analysis (FTIR) analysis. The branded vegetable oils were (U1 - U13), U14- U17 = unbranded vegetable oils; U18- U19 = branded palm oils; U20- U24 = unbranded palm oils. Percentage moisture content, colour, odour and rancidity were the physicochemical parameters analysed. The percentage moisture content was found to be within the ranges of 0.00 – 0. 33%. Higher moisture content was observed in samples U13 and U24. The colours and odour are in line with the standard of SON except for sample U22 which had an objectionable odour. There were records of rancidity in four (4) vegetable oils U1, U5, U16 and U17 and two (2) palm oils, U20 and U22 analyzed. The FTIR analysis indicated that there is unsaturated C-H stretching vibration peak of carbon chain at 3006 and 3648 cm-1 for the unheated samples. In comparison, peaks attributable to the presence of an aromatic group was not identified in samples U5 and U15 but was identified in H5 and H15 respectively. There was an increase in the peaks of sample U5 from 3008 and 2925 cm-1 to 3853 and 3646 cm-1 in sample H5.   Heating of edible oils at smoke point changes the composition of the oil slightly by the formation of new additional compounds.