地面有效辐射气候学模型评估和参数优化

Evaluation and parameter optimization of surface effective radiation climatology models

  • 摘要: 基于中国19个辐射站1993-2012年的地面辐射平衡资料和气象资料,分析评估了布朗特法、彭曼法、别尔良德法、FAO24法、FAO56-PM法、邓根云法和童宏良法7种参数化方案计算中国地面有效辐射的适用性;并以均方根误差最小为目标函数,利用步长加速法和多元回归法迭代求解最优参数,建立适合于中国的最优参数化逐日有效辐射估算方法。结果表明:参与评估的7种方案都不同程度低估了中国的有效辐射;从全中国总体误差水平看,童宏良法的平均绝对百分比误差和均方根误差小于其他6种方案,分别为27.0%和24.5 W/m2,估算效果较好;其次是彭曼法和邓根云法;FAO56-PM法精度较低,不适用于中国的有效辐射估算。针对单站来说,邓根云法在东部平原地区的精度最高,童宏良法由于考虑了海拔高度的订正,适用于西部高原地区。相关分析表明水汽压是影响有效辐射估算误差的最关键因素,因此根据水汽压的地理分布规律,分东部区和西部区建立分区方案。基于观测资料建立的全中国方案和分区方案的均方根误差分别为20.8和21.4 W/m2,精度均高于已有参与评估的7种方案;而且在绝大多数站点,分区方案的误差小于全中国方案,所以划分东部区和西部区进行有效辐射模型参数化很有必要。同时发现,分区方案在西部区明显优于邓根云法,在东部区明显优于童宏良法,因此推荐其作为中国有效辐射的计算方法。

     

    Abstract: Based on surface radiation balance data and daily meteorological observations collected at 19 radiation stations in China from 1993 to 2012, the applicability of seven empirical methods for the estimation of surface effective radiation (including Brunt model, Penman modified model, Bepлянд model, FAO24 modified model, FAO56-PM model, Deng Genyun model, and Tong Hongliang model) was assessed and a revised method applicable to China was established by re-fitting the formula using new observational data. The iterative solution method and the multivariate regression analysis method with the minimum root mean square error (RMSE) was used as the objective function in the revised method. Results showed that the effective radiation over China was underestimated by all the above seven models. The mean absolute percentage error (MAPE) and RMSE derived from the Tong Hongliang model was 27.0% and 24.5 W/m2 respectively, which are less than those from the other six models. Thereby the Tong Hongliang model was the best among the seven models for estimating the effective radiation over China, followed by the Penman modified model and the Deng Genyun model. The FAO56-PM model was not applicable to China due to its low accuracy. For individual stations, the accuracy of the Deng Genyun model was the highest in the eastern plain area while the Tong Hongliang model was suitable for the plateau area because it includes the altitude correction in the atmospheric moisture calculation. Correlation analysis indicated that the water vapor pressure was the most critical factor affecting the estimated error of the effective radiation. Therefore, the regional models were established for the eastern and western areas respectively based on geographical distribution of the water vapor pressure. The RMSE calculated by the revised models, which were developed based on observations, for entire China and for the eastern and western areas were 20.8 and 21.4 W/m2 respectively. Results of the new models were more accurate than that of the seven models mentioned above. Furthermore, the regional model produced smaller errors than the model for entire China at most of the stations, indicating that it is necessary to distinguish the eastern and western areas in the development of new methods for determination of effective radiation. The western regional model was obviously more accurate than Deng Genyun model in the western area and the eastern regional model was obviously more accurate than Tong Hongliang model in the eastern area. Therefore the regional models developed in this study were recommended as the standard climatology models for calculation of the effective radiation over China.

     

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