A Comparative Study of some Meteorological Parameters for Predicting Global Solar Radiation in Kano, Nigeria Based on Three Variable Correlations

In this present study, twenty empirical regression equations based on three variable correlations were developed and used to estimate the monthly average daily global solar radiation on a horizontal surface using measured monthly average daily global solar radiation, sunshine duration, wind speed, maximum and minimum temperatures, rainfall, cloud cover and relative humidity parameters during the period of thirty one years (1980 – 2010) for Kano, Nigeria (Latitude 12.030N, Longitude 08.120E and altitude 472.5 m above sea level). The comparative performance of the developed models has been evaluated on the basis of statistical parameters using Mean Bias Error (MBE), Root Mean Square Error (RMSE), Mean Percentage Error (MPE), t – test and Nash – Sutcliffe Equation (NSE). The values of the correlation coefficient (R) and coefficient of determination (R2) were also obtained for each of the developed models. The MPE values for all the developed models lie within the acceptable range . The t – test produces perfect model performance at 95% and 99% confidence level for all the developed models. Three equations were recommended from this study, firstly, the model (Eqn. 20) with the highest value of R and R2, secondly, the model (Eqn. 24) with the least value of RMSE and the highest value of NSE and thirdly, the model (Eqn. 31) with the least values of MPE and t – test. These developed models can be used for estimating monthly average daily global solar radiation for Kano, North – Western, Nigeria and other locations with similar weather conditions where the solar radiation data is unavailable. Keywords: global solar radiation, Kano, variable correlation, Mean Bias Error (MBE) and coefficient of determination

The Impact of some Meteorological Variables on the Estimation of Global Solar Radiation in Kano, North Western, Nigeria

This study examines the impact of measured monthly average daily global solar radiation, sunshine duration, wind speed, maximum and minimum temperatures, rainfall, cloud cover and relative humidity parameters on the estimation of global solar radiation during the period of thirty one years (1980 – 2010) for Kano, Nigeria (Latitude 12.030N, Longitude 08.120E and altitude 472.5 m above sea level) using different selected proposed empirical models. The accuracy of the proposed models are tested using statistical indicator; Mean Bias Error (MBE), Root Mean Square Error (RMSE), Mean Percentage Error (MPE), t – test, correlation coefficient (R) and coefficient of determination (R2). The developed models are based on one variable correlation, two variable correlations, three variable correlations, four variable correlations, five variable correlations and six variable correlations, in each case one or two empirical models has been recommended based on their outstanding performance in line with the statistical test subjected to. The model (Eqn. 36) with the highest values of R and R2 and lowest values of MBE, RMSE, MPE and t – test as compared with other developed model is considered the best performing model. It was observed that the newly recommended developed models (Eqns. 13, 17, 21, 26, 27, 31, 35 and 36) can be used for estimating daily values of global solar radiation with higher accuracy and has good adaptability to highly changing climatic conditions for Kano and regions of similar climatic information. Keywords: global solar radiation, sunshine duration, wind speed, rainfall and coefficient of determination

Time Series and Empirical Orthogonal Transformation Using Meteorological Parameters across the Climatic Zones in Nigeria

Time series and empirical orthogonal transformation analysis was carried out for four (4) selected tropical sites, which are situated across the four different climatic zones, viz. Sahelian, Midland, Guinea savannah and Coastal region in Nigeria using measured monthly average daily global solar radiation, maximum and minimum temperatures, sunshine hours, rainfall, wind speed, cloud cover and relative humidity meteorological data during the period of thirty one years (1980-2010). Seasonal Auto Regressive Integrated Moving Average (ARIMA) models were developed along with their respective statistical indicators of coefficient of determination (R2), Root Mean Square Error (RMSE), Mean Absolute Percentage Error (MAPE) and Mean Absolute Error (MAE). The results indicated that the models were found suitable for one step ahead global solar radiation forecast for the studied locations. Furthermore, the results of the time series analysis revealed that the model type for all the meteorological parameters show a combination of simple seasonal with one or more of either ARIMA, winter’s additive and winter’s multiplicative with the level been more significant as compared to the trend and seasonal variations for the exponential smoothing model parameters in all the locations. The results of the correlation matrix revealed that the global solar radiation is more correlated to the mean temperature except for Akure where it is more correlated to the sunshine hours; the mean temperature is more correlated to the global solar radiation; the rainfall is more correlated to the relative humidity and the relative humidity is more correlated to the rainfall in all the locations. The results of the component matrix revealed that three seasons are identified in Nguru located in the Sahelian region namely, the rainy, the cool dry (harmattan) and the hot dry seasons while in Zaria, Makurdi and Akure located in the Midland, Guinea savannah and Coastal zones two distinct seasons are identified namely, the rainy and dry seasons

Developing Empirical Models for Estimating Photosynthetically Active Radiation over Akure, South Western, Nigeria

In this study, the measured monthly average daily global solar radiation and extraterrestrial solar radiation using the generalized 45% and 40% dataset was utilized to estimate the photosynthetically active radiation (PAR) and extraterrestrial photosynthetically active radiation (PAR0) for Akure (Latitude 7.170N, Longitude 5.180E, and 375.0 m above sea level) Ondo State located in South Western, Nigeria. The monthly average daily sunshine hours, maximum and minimum temperature data were used to develop nine (9) new PAR sunshine based models and three (3) PAR temperature-based models. The meteorological parameters used in this study covered a period of thirty-one years (1980 – 2010). The newly developed models were tested using statistical indicators of the coefficient of determination (R2), Mean Bias Error (MBE), Root Mean Square Error (RMSE), Mean Percentage Error (MPE), t-test, Nash – Sutcliffe Equation (NSE) and Index of Agreement (IA). The PAR sunshine based models that took a quadratic form and the linear logarithmic PAR temperature-based models were found more suitable for estimating PAR for the location under study. Comparing the PAR sunshine based and temperature-based models indicated that the PAR sunshine based model is more suitable for PAR estimation in Akure. Furthermore, the results showed that PAR is high during the dry season and low during the rainy season. Based on the measured and estimated PAR models; the minimum values were found in July and August while the maximum values in February, March and November. The descriptive statistical analysis shows that the PAR and all the estimated sunshine based PAR data spread out more to the left of their mean value (negatively skewed). Similarly, they have negative kurtosis which indicates a relatively flat distribution and the possibility of platykurtic distribution. The PAR and the PAR logarithmic temperature-based model (equation 17a) data spread out more to the left of their mean value (negatively skewed), while the PAR linear exponent and linear temperature-based models (equation 17b and 17c) data spread out more to the right of their mean value (positively skewed). The PAR and all the estimated PAR temperature-based data have negative kurtosis which indicates a relatively flat distribution and the possibility of platykurtic distribution

Performance Analysis of Tropospheric Radio Refractivity on Radio Field Strength and Radio Horizon Distance and Its Variation with Meteorological Parameters over Osogbo, Nigeria

Radio refractivity estimation is paramount in the planning and design of radio link/systems for the purpose of achieving optimal performances. In this study, the monthly average daily atmospheric pressure, relative humidity and temperature data obtained from the National Aeronautics and Space Administration (NASA) during the period of twenty two years (July 1983 – June 2005) for Osogbo (Latitude 7.47 0N, Longitude 4.29 0E, and 302.0 m above sea level) were used to estimate the monthly tropospheric radio refractivity and to investigate its variation with other meteorological parameters of monthly average daily atmospheric pressure, relative humidity, absolute temperature, saturation vapour pressure and radio refractive index. The field strength variability (FSV) and the radio horizon distance were also computed. The monthly variation of FSV using two years of data (2003 – 2004) was also investigated. The results of this study revealed that the values of radio refractivity are more during the rainy season than in the dry season. It was found that the maximum average value of tropospheric radio refractivity of 370.98 N-units and the minimum average value of 332.36 N-units occurred in the months of May and January during the rainy and dry seasons respectively. 71.45 % of the total value of the radio refractivity was contributed by the dry term while the major variation is by the wet term radio refractivity. The average refractivity gradient computed for the study area under investigation was −42.69 N-units/km and the average effective earth radius (k – factor) was 1.37 which corresponds to the conditions of super refraction. The annual maximum mean value of FSV is 7.72 dB and the minimum monthly mean value of 0.07 dB was obtained for the study area. The implication of this FSV values is that the output of a receiving antenna in Osogbo may generally be subjected to changes not less than 0.07 dB in a year and not greater than 7.72 dB. The descriptive statistical analysis shows that the radio refractivity, relative humidity, absolute temperature and radio refractive index data spread out more to the left of their mean value (negatively skewed), while the atmospheric pressure data spread out more to the right of their mean value (positively skewed). The radio refractivity, relative humidity and radio refractive index data have positive kurtosis which indicates a relatively peaked distribution and the possibility of a leptokurtic distribution. The atmospheric pressure and absolute temperature data have negative kurtosis which indicates a relatively flat distribution and possibility of platykurtic distribution

Estimation and Investigation of Photosynthetically Active Radiation over Benin, Nigeria

Photosynthetically active radiation (PAR) is an important input parameter for estimating plant productivity due to its key role in the growth and development of plants. In this study, the measured monthly average daily global solar radiation, relative humidity, wind speed, minimum and maximum temperature dataset was utilized to estimate and investigate the Photosynthetically active radiation (PAR) for Benin (latitude 6.32 N, longitude 5.10 E and 77.8 m) located in the coastal region of Nigeria. The meteorological parameters used in this study were obtained from the archives of National Aeronautics and space Administration (NASA) for a period of thirty-eight years (1984-2021). The newly developed temperature PAR based models were tested using statistical indicators of the coefficient of determination (R2), Mean Bias Error (MBE), Root Mean Square Error (RMSE), Mean Percentage Error (MPE), t – test and index of Agreement (IA) to ascertain the suitability and applicability of the models. The results show that photosynthetically active radiation (PAR) is higher during the dry season and is low during the rainy season. Based on the regression models developed, the linear model equation that contains the mean temperature and temperature ratio was observed to be the best for PAR estimation in Benin with R2, MBE, RMSE, MPE, t-test and IA value of 71.9 , -0.0283 MJ , 0.4842 MJ 0.0670 0.1941 and 88.3428 respectively