基于LightGBM算法的大气可降水量预测方法研究

Research on precipitable water vapor prediction method based on LightGBM algorithm

大气可降水量(precipitable water vapor,PWV)为单位横截面积垂直气柱内地面至对流层顶部的液态水汽含量,可反映大气中的水汽浓度.本文首先利用2014—2019年长三角地区7个探空站资料,分析了PWV与对流层天顶总延迟(zenith tropospheric delay,ZTD)、天顶静力学延迟(zenith hydrostatic delay,ZHD)、对流层湿延迟(zenith wet delay,ZWD)、水汽压(Es)、大气压(Ps)、地面温度(Ts)、加权平均温度(Tm)之间的相关性,再基于梯度提升机(light gradient boosting machine,LightGBM)构建了一套适用于长三角地区的PWV预测模型,并分析了LightGBM-PWV模型的预测精度.结果表明,PWV与Tm、Ts、Ps、Es、ZHD、ZWD和ZTD之间的相关系数(R)分别为0.74、0.76、–0.59、0.76、–0.43、1.00和0.94;全年、分季度和分月LightGBM-PWV模型的平均偏差分别为0.10 mm、0.11 mm和0.12 mm,均方根误差(root mean square error,RMSE)分别为0.25 mm、0.26 mm和0.31 mm,模型精度依次递减,异于传统线性拟合PWV模型;全年LightGBM-PWV预测模型精度最高,可用于长三角地区的GNSS-PWV预测、分析和研究.

The precipitable water vapor(PWV)represents the content of liquid water vapor in a unit cross-sectional area vertically from the Earth’s surface to the top of the troposphere,reflecting the concentration of water vapor in the atmosphere.In this study,data from seven radiosondes in the Yangtze River Delta region from 2014 to 2019 were utilized to analyze the correlations between PWV and zenith tropospheric delay(ZTD),zenith hydrostatic delay(ZHD),zenith wet delay(ZWD),water vapor pressure(Es),atmospheric pressure(Ps),surface temperature(Ts),and weighted mean temperature(Tm).A new Light Gradient Boosting Machine(LightGBM)-based PWV prediction model for the Yangtze River Delta region was established,and then the prediction accuracy of the LightGBM-PWV model was analyzed.The results show that the correlation coefficients(R)between PWV and Tm,Ts,Ps,Es,ZHD,ZWD,and ZTD were 0.74,0.76,–0.59,0.76,–0.43,1.00,and 0.94 respectively.The average biases of the yearly,seasonal,and monthly LightGBM-PWV model were 0.10 mm,0.11 mm,and 0.12 mm respectively,and their RMSE are 0.25 mm,0.26 mm,and 0.31 mm.The accuracy of the yearly,seasonal,and monthly LightGBM-PWV model decreased sequentially,different from the traditional linear fitting PWV models.The yearly LightGBM-PWV forecasting models demonstrate the highest accuracy.It can be applied for the GNSS-PWV forecasting,analysis,and research in the Yangtze River Delta region.