基于温度作为辅助变量的中国降水δ^(18)O空间分布特征

Spatial Distribution of δ^(18)O in China's Precipitation Based on a Secondary Variable of Temperature

本研究利用从WorldClim获得的高分辨率气象数据分析稳定同位素温度效应,研究发现最热季度的平均气温与中国62个站点同位素年平均值之间表现出很好的相关性(R2=0.79)。在此基础上利用地统计学方法,也就是采用温度作为辅助变量的空间插值算法——局部平均的简单克里金法(Simple Kriging with locally varying mean,SKlm),对中国降水中稳定同位素年平均值空间分布进行了模拟,得到了较高分辨率的中国降水中年均δ18O空间分布图,该图能够较好地表现区域同位素变化模式,能够反映如降水汽团的来源、性质等的气候环境背景,也能在一定程度上反映包括当地的纬度、地形、海拔高度等在内的局部地理因素。

To acquire knowledge of temperature effect on stable isotope, the relation between various temperature related variables and isotopic composition of modern precipitation was explored, based on the high-resolution meteorological data and the isotope values from WorldClim and China＇s stable isotope observation sites. We used a linear model to fit the relation between the different temperature variables and the isotopic composition. Although the annual mean temperature does well to explain the annual mean isotope signal, the better correlation between the mean temperature in the hottest quarter and the annual mean isotope of 63 sites in China is found （R2=0.79）. The temperature during the coldest quarter is used as an ancillary variable in simple kriging with varying local means （SKIm）. In SKIm, the residual isotope values from the regression with mean temperature in the hottest quarter are kriging interpolated, which are then added to the high-resolution spatial distribution of stable isotope （δ^18O） in China＇ s precipitation. So more local isotope effects are accounted for by the spatial interpolation of the residual isotope values. With the good correlation between mean temperature in the hottest quarter and annual mean isotope values, the spatial distribution map can well present the pattern of variability of isotope in China. The low prediction error and a symmetrical distribution of the differences between the true and predicted values demonstrate the successful application of the SKIm approach. In summary, using surface temperature as a factor does improve the prediction of the China＇ s isotope variation in precipitation compared to a combination of latitude and altitude, and also indicates the environmental background of regional climate and local geographic factor.