Estimation of daily global solar irradiance from the air temperature in the state of Paraná, Brazil

ABSTRACT Global solar irradiance (GSI) is a fundamental source of energy on Earth. Despite its importance, sunshine or solar irradiance data are rarely available from weather stations. In the absence of available data, there are empirical methods that can be used to estimate solar irradiance. The objective of this study is to calibrate the parameters and to evaluate the performance of four empirical models of solar irradiance estimation (those of Chen, Hargreaves, Hunt, and Richardson) from air temperature data for eight localities in the state of Paraná, Brazil. Data were obtained from the Meteorological Database for Teaching and Research (BDMEP). For the comparison of means among the models, the Kruskal-Wallis non-parametric test was used. Dunn’s multiple comparison tests were used to analyze which models presented different means from the others. The performance of each model was assessed using the indices Pearson correlation coefficient (r), mean bias error (MBE), root mean square error (RMSE), Wilmott concordance index (d), performance index (c) and the Nash-Sutcliffe efficiency (NSE) coefficient. It was observed that the models proposed by Chen and Hunt presented the best performances in the estimation of GSI for the studied Paraná state localities, given that they yielded results which are closer to the observed historical data.

摘要 全球太阳总辐照度（Global Solar Irradiance, GSI）是地球的核心能量来源。尽管其重要性不言而喻，但气象站点鲜有提供日照或太阳辐照度观测数据。在缺乏实测数据的场景下，可通过经验方法估算太阳辐照度。本研究旨在基于巴西巴拉那州8个观测站点的气温数据，对Chen、Hargreaves、Hunt及Richardson提出的4种太阳辐照度估算经验模型开展参数校准，并评估其性能表现。本研究所用数据取自教学与研究气象数据库（Meteorological Database for Teaching and Research, BDMEP）。为对比各模型的均值差异，本研究采用Kruskal-Wallis非参数检验；通过Dunn多重比较检验，进一步甄别存在均值差异的模型。本研究采用皮尔逊相关系数（Pearson Correlation Coefficient, r）、平均偏差误差（Mean Bias Error, MBE）、均方根误差（Root Mean Square Error, RMSE）、威洛特一致性指数（Wilmott Concordance Index, d）、性能指数（Performance Index, c）以及Nash-Sutcliffe效率系数（Nash-Sutcliffe Efficiency, NSE）对各模型的性能进行评估。结果显示，针对巴拉那州研究站点的全球太阳总辐照度估算任务，Chen模型与Hunt模型表现最优，其估算结果与实测历史数据的吻合度最高。