修正BW方法在中国大气降水δ^(18)O空间分布研究中的应用

The application of modified BW method in studying spatial distribution of δ^(18)O in precipitation over China

为研究中国大气降水δ18O的空间分布,利用81个大气降水和冰芯站点δ18O资料和BW回归模型,拟合出大气降水δ18O与纬度和海拔的定量关系:δ18O=-0.024LAT2+1.541LAT-0.002 ALT-29.678.同时,为了优化BW回归模型的拟合结果,对BW回归模型的残差做了内插并比较了不同插值方法的精度.结果表明:以降水量为辅助变量的协同克里格法对残差的预测效果最好,与广泛采用的反距离加权法相比,该方法预测的BW残差与实际残差间的RMSE减小了0.14‰,ME也更接近于0.最后,利用最优的插值方法生成了BW回归模型的残差分布图,并将其与BW的模拟结果叠加得到了中国降水δ18O的空间分布图.其结果总体上反映了中国大气降水中δ18O的分布状况,为降水δ18O的现代过程研究以及古气候和古水文的研究提供了资料参考.

Precipitation is an important section in water cycle. Isotope ratios in precipitation are associated with the meteorological process, which display an obvious spatial and temporal distribution. Isotope ratios in precipitation can be used in deriving the atmospheric processes, tracing the vapor sources and reflecting the local weather and climate conditions. In order to study the spatial distribution of δ^18O in precipitation over China, BW model are used to establish a model of the quantitative relationship between δ^18O in precipitation and latitude or altitude. The model can be described as： δ^18O = -0.024LAT2 ＋ 1. 541LAT -0.002ALT -29. 678. Simultaneously, the residual of BW models with different methods are interpolated, and the interpolation accuracies are compared. Comparing to previous research, the RMSE of this method is reduced by 0.14%o with ME close to 0. Finally the spatial distribution of residual of BW model with the most optimized method is made and a spatial distribution map of δ^18O in precipitation over China is drawn, which provides important information for studying ancient climate and stable isotopic hydrology.