Validation and Investigation of Correlations to Determine Daily Mean Values of Climatic Parameters

Abstract

This study evaluated selected correlation models for estimating daytime profiles of global solar radiation on a horizontal surface and ambient temperature at a measurement site in Ouagadougou, Burkina Faso. Experimental data were collected using a pyranometer, a K-type thermocouple and a data logger installed at Joseph KI-ZERBO University. Measurements were recorded at five-minute intervals during selected days in December, January, March and April, and monthly average daytime profiles were obtained. Two trigonometric correlations previously used in existing literature were first applied to describe the temporal variation of solar radiation and ambient temperature. In addition, Gaussian-type correlations were developed using non-linear regression in MATLAB to represent the measured profiles. For global solar radiation, the literature-based sine model produced coefficients of determination between 0.96 and 0.98, with RMSE values ranging from 36.3 to 51.3 W/m². The proposed Gaussian model produced R² values between 0.96 and 0.98, with RMSE values ranging from 33.0 to 51.0 W/m². For ambient temperature, the literature-based model gave R² values between 0.94 and 0.97 and RMSE values between 0.55 and 0.76 °C, while the Gaussian model gave R² values between 0.96 and 0.98 and RMSE values between 0.37 and 0.63 °C. The results indicate that both approaches describe the measured daytime profiles with acceptable agreement.