基于循环神经网络和集成学习的气温预报误差订正方法与应用

    Temperature forecast error correction method and application based on recurrent neural network and ensemble learning

    • 摘要: 温度是影响酿酒葡萄生长的关键因素,高温、低温和霜冻等灾害性天气会对酿酒葡萄的种植造成严重影响。气温预测与订正技术在农业生产中广泛应用,为农业生产提供精准的气温预报服务。该研究针对农业气象气温预报存在的偏差问题,对欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts, ECMWF)模式在宁夏境内15个地区2018年逐日预报数据进行误差分析,使用均方根误差和平均绝对误差验证ECMWF模式预报数据在宁夏地区存在系统性偏差;利用循环神经网络(recurrent neural network, RNN),长短期记忆网络(long short-term memory, LSTM)和门控循环单元(gated recurrent unit, GRU) 3种模型对最高预报气温和最低预报气温开展订正研究;为进一步提高模型的精度,构建基于上述3种模型的集成学习模型。采用平均绝对误差与预报订正改善率对订正效果进行评估,并与传统订正方法随机森林(random forest, RF)进行对比。结果表明,所研究的RNN、LSTM、GRU及集成学习模型均能有效减小ECMWF模式在宁夏地区距地面2 m处最高、最低温度预报的系统性偏差,且订正效果优于RF。其中RF的平均预报订正改善率仅为25.86%,RNN的订正效果相对较弱且在部分场景下表现不佳,平均预报订正改善率为32.24%,LSTM和GRU的订正效果相近,均达到37.2%,集成学习模型的订正效果最好,可达到38.61%,说明集成方法在气温预报订正中的有效性。此外,基于该研究构建的集成学习模型,进行工程应用系统设计,开发了适用于宁夏地区的农业气象高低温预报误差订正系统,针对宁夏地区的预报数据实现快速准确的订正,为宁夏的酿酒葡萄种植等农业生产以及灾害性天气的防灾减灾决策提供可靠的参考依据。

       

      Abstract: Temperature is one of the key influencing factors on the growth of wine grapes. Disasters, such as high temperatures, low temperatures, and frost, can severely impact the wine grape cultivation. Temperature prediction and correction technologies are widely used in agricultural production, providing accurate temperature forecast services. This study focused on the issue of bias in agricultural meteorology temperature forecasting. A systematic investigation was also made to correct the temperature forecast errors and application using recurrent neural networks and ensemble learning. The forecast and actual datasets were collected in the daily forecasts of 15 regions in Ningxia in 2018. The root mean square error and mean absolute error were used to verify the systematic deviation in the forecast data of the European Centre for Medium-Range Weather Forecasts (ECMWF) model. The systematic deviations were experimentally verified in the ECMWF model's 2m maximum and minimum temperature forecasts. The results show that the ECMWF forecasts exhibited systematic deviations: The forecasts that initialized at 00:00Z were provided for better predictions of the minimum temperature, but there were generally larger errors in the maximum temperature. While the forecasts that were initialized at 12:00Z performed better for the maximum temperature, there were significant biases in the minimum temperature. The correction of the maximum and minimum temperature forecasts was conducted using three models: a recurrent neural network (RNN), a long short-term memory (LSTM), and a gated recurrent unit (GRU). An ensemble learning model was constructed to integrate these three models in order to further improve the accuracy of the model. The correction was evaluated by the mean absolute error and the forecast correction improvement rate. A comparison was made between the conventional correction method (Random Forest, RF) and the proposed approach. Experiments showed that all four models effectively reduced the systematic deviation of the ECMWF model's maximum and minimum temperature forecasts at 2 m above the ground in the study areas. Their correction performance was generally superior to that of RF. But there were some differences in the performance among the four models. The RF exhibited the weakest performance of the correction, where an average forecast correction was improved by 25.86%. The RNN showed the relatively limited correction in some scenarios, with an average improvement of 32.24%. LSTM and GRU achieved a similar correction performance, both reaching 37.2%. The ensemble learning model achieved the best correction performance, reaching 38.61%. The effectiveness of ensemble learning was highlighted in the temperature forecast correction. The strong performances of the four models significantly outperformed the RF. The correction results confirmed the effectiveness of recurrent neural networks in the meteorological data. The ensemble learning model (Ensemble) exhibited superior robustness and stability over the various scenarios, indicating the relatively high correction performance. The ensemble model with the highest average forecast correction enhanced both predictive accuracy and robustness, compared with the individual models. In addition, an application system was designed and implemented to correct 2m maximum and minimum temperature forecasts. A rapid and accurate correction of regional forecast data was realized using the ensemble learning model. The finding can provide a reliable reference for the wine grape cultivation, particularly for disaster prevention and decision-making against extreme weather events.

       

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