日散射辐射模型经验系数确定方法

为得到适应于无辐射观测地区散射辐射模型经验系数的确定方法,根据中国国家气象信息中心发布的中国地面气象、辐射数据,采用回归分析的方法建立单站点模型、修正模型,选择决定系数（R²）、平均绝对误差百分比（MAE）、均方根误差百分比（RMSE）作为评价模型准确度的指标进行对比研究. 基于17个台站2000—2017年的日照时数、日总辐射、日散射辐射数据,以每个台站前10年的数据建立12个基于日照时数比、晴空指数的单站点模型、3个包含地理参数（经度、纬度、海拔高度）的修正模型,后4年的数据用来评价模型的准确度. 分析比较不同模型、不同台站的MAE、RMSE、R²的高低,发现模型的形式对准确度有较大影响,多项式模型的准确度高于对数、指数形式,一次函数的准确度低于二次、三次函数形式；单站点模型中,以晴空指数、日照时数比为输入参数的模型最准确,修正模型属基于晴空指数的模型最准确；对于未观测台站可以用包含经度、纬度、海拔高度、晴空指数的模型推算散射辐射.

The estimation method for empirical coefficient of daily diffuse solar radiation model in China

The study is aimed to develop an ideal method to estimate empirical coefficient of diffuse solar radiation model in the Chinese cities where there is no record of solar radiation data. The ground meteorological and solar radiation data from China Meteorological Data Service Center and the method of regression analysis were used to develop and verify the model. The sunshine duration, global solar radiation and diffuse solar radiation from 2000 to 2017 of 17 stations were selected. 12 individual models based on sunshine duration ratio and clearness index and 3 modified models based on geographical parameters (longitude, latitude, and altitude) were built using the data of the first ten years of each station. The data of the last four years of each station were used to evaluate the accuracy of the models. The models were evaluated using coefficient of determination (R²), mean absolute percentage bias error (MAE), and root mean percentage squared error (RMSE). Results show that the form of the model had a great influence on accuracy. The accuracy of the polynomial model was higher than that of the logarithmic and exponential forms, and the accuracy of the primary function was lower than that of the quadratic and cubic functions. Besides, the model using clearness index and sunshine duration ratio as its input parameters was the most accurate among individual models, and the model based on clearness index was the most accurate among modified models. For unobserved stations, the diffuse solar radiation can be estimated by the proposed model based on latitude, longitude, altitude, and clearness index.