variation of the earth’s irradiance over some selected towns in nigeria

The extraterrestrial radiation is the solar radiation received at the top of the earth’s atmosphere on horizontal surface. this quantity over selected stations in the tropics was investigated. daily data of the extraterrestrial radiation on the earth horizontal surface for the year 2018 for stations: iwo, abuja, enugu, port-harcourt, sokoto and maiduguri obtained from the archive of helioclim website were analyzed using matlab and statistical packages for social science (spss version 20.0) to estimate the extraterrestrial radiation of the station considered. the results of the matlab revealed that the value of the coincidence is − 2×10^4 𝑊𝑚^−2 across all stations. in january, the values between 15 - 20 peaks were observed in the year with the irradiation (− 4×10^4 𝑊𝑚^−2) and the maximum (2×10^4 𝑊𝑚^−2). the results revealed the root mean square error rmse for sokoto (139.99), abuja (162.72), iwo (177.07), maiduguri (171.34), enugu (191.07), port-harcourt (212.27). the results also revealed that quadratic trend equation which accounted in the range 95.9% - 41.9%. the results then concluded that sokoto and maiduguri have the highest solar irradiance as revealed by the result.