The Merging of the MODIS EVI and δ18O in Precipitation

• Main Authors: Wei-Ping Chan, 詹偉平
• Other Authors: Hsiao-Wei Yuan
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/25987760685698555504

碩士 === 國立臺灣大學 === 森林環境暨資源學研究所 === 99 === The natural variation in stable water isotope ratio data, also known as water isoscape, is a spatiotemporal fingerprint and a powerful natural tracer that has been widely applied in disciplines as diverse as hydrology, paleoclimatology, ecology and forensic investigation. Although much effort has been devoted to developing a predictive water isoscape model, it remains a central challenge for scientists to generate high accuracy, fine scale spatiotemporal water isoscape prediction. Here we develop a novel approach of using the MODIS-EVI (the Moderate Resolution Imagining Spectroradiometer-Enhanced Vegetation Index), to predict δ18O in precipitation at local and global scales. Using a structural equation model, we show that the EVI and precipitated δ18O are highly correlated and thus the EVI is a good predictor of precipitated δ18O. We then test the predictability of our EVI-δ18O model and demonstrate that our approach can provide higher accuracy with finer scale spatial (250x250m) and temporal (16 days) δ18O predictions than all existing models at both regional scale (annual and monthly predictive ability are r=0.96 and r=0.80±0.17, n=13 sites, respectively) and global scales (annual and monthly predictive ability are r=0.96 and r=0.76±0.02, n=27 sites, respectively). We suggest the merging of the EVI and δ18O in precipitation can greatly extend the spatial and temporal data availability and thus enhance the applicability for both the EVI and water isoscape.