基于机器学习的中国区域降水相态识别方案

Machine Learning-Based Methods for Precipitation Phase Discrimination in China

  • 摘要: 降水相态的准确识别对水热平衡、水文循环及冰冻圈过程的模拟具有重要意义。为提升中国区域降水相态的识别精度,该研究基于中国地面气候资料日值数据集,比较了5种降水相态识别的机器学习方法在传统方法难以准确识别的温度区间(-7℃,10℃)中的表现。结果显示,MLP(多层感知器)方法在中国区域的降水相态识别中表现突出,测试集的整体识别准确率为88.1%,较传统方法提高了4.4%。青藏高原区域的识别准确率达91.4%,较传统方法提升了12.8%。MLP模型显著提高了降雨和雨夹雪的识别精度,尤其在降雨、雨夹雪较多的青藏高原东部和华南地区。MLP的识别性能受降雨和降雪样本分布影响,对南方降雨与北方降雪的识别误差较低。分析显示,包含温度、湿度与气压信息的湿球温度对MLP模型的影响最大,降水量也会对雨夹雪的识别概率也具有重要影响。同时,MLP能够有效再现降水相态对海拔和相对湿度依赖的观测特征,包括降水相态划分温度阈值随海拔升高而升高的趋势,以及雨夹雪发生概率随相对湿度增加而提高的规律,在反映关键物理特性方面具有一定的可解释性。总体而言,基于MLP的机器学习方法显著提升了中国区域降水相态的识别精度,可以服务于水文与冰冻圈过程的理解与模拟。

     

    Abstract: Accurate identification of precipitation types is crucial for the simulation of water-energy balance, hydrological cycle, and cryospheric processes. To enhance the accuracy of precipitation phase recognition over China, this study explores the performance of five machine learning methods within temperature ranges where traditional approaches struggle to accurately differentiate precipitation phases (-7℃,10℃) based on the dataset of daily surface climate variables of China. The results show that the MLP model performs well in identifying precipitation types across China, achieving an overall accuracy of 88.1% on the test set, a 4.4% improvement over traditional methods. In the Tibetan Plateau, the accuracy reached 91.4%, an increase of 12.8% compared to traditional methods. The MLP model notably improves the identification of rain and sleet, especially in areas with frequent rainfall and sleet in eastern Tibetan Plateau and southern China. The performance of MLP model is influenced by sample distribution, achieving lower identification errors for rainfall in South China and snowfall in North China. Analysis shows that wet-bulb temperature, which incorporates information on temperature, humidity and pressure, has the greatest impact on MLP model’s performance. Precipitation amount also significantly affects the probability of sleet classification. Additionally, the MLP model successfully reproduces the observed dependence of precipitation types on elevation and relative humidity. Specifically, it captures the increase in the temperature threshold for precipitation phase discrimination with elevation, as well as the higher probability of sleet occurrence with increasing humidity, demonstrating its ability to represent key physical characteristics with a certain degree of interpretability. Overall, MLP-based machine learning method significantly improves the accuracy of precipitation type identification across China, facilitating imporved understanding and modeling of hydrological and cryospheric processes.

     

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