Regional Scale High Resolution δ¹⁸O Prediction in Precipitation Using MODIS EVI

<div><p>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 the regional scale. 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 high accuracy with fine spatial (250×250 m) and temporal (16 days) scale δ¹⁸O predictions (annual and monthly predictabilities [<em>r</em>] are 0.96 and 0.80, respectively). We conclude 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.</p> </div

The fine scale regional δ¹⁸O prediction map of Taiwan in August, 2009.

<p>The inset highlights the fine resolution (250 m) of modeled result.</p

SEM analysis of the relationship among climatic, topographic factors, the iEVI and δ¹⁸O.

<p><b>a,</b> The relationships among the iEVI and δ¹⁸O and other climatic, topographic factors. The “Err” circles represent the parts that were not explained by above factors in both the iEVI and δ¹⁸O, but can be explained by each other. <b>b,</b> The relationship between topographic factors, the iEVI and δ¹⁸O (the climatic factors are replaced by the iEVI). All values are under two tailed t-test, and are significant (<i>p</i><0.001). The values shown here are correlation coefficients (<i>r</i>), unless noted as <i>r²</i> representing the overall variability explained by other factors that connect to the box.</p

The conceptual basis of merging the EVI and δ¹⁸O.

<p>The direction of influence of each factor is represented by the arrows. Functions that are directly influenced by spatial and climatic factors are listed in the parentheses within the EVI and δ¹⁸O boxes. “A” is the constraint of spatial extent for EVI data, where is restricted by the amount of snow cover. “B” is the description of the characteristics of output (δ¹⁸O) including high resolution, large spatial scale, and various temporal scales (16-day, monthly, seasonal or yearly estimation). “C” is the limitation of δ¹⁸O data. It should be monthly data or the model should be modified to a different temporal scale. “D” indicates the long temporal extent of output of the EVI data. Only temperature, precipitation, and altitude are included in our SEM analysis but other topographic and climatic factors may also be included. References for each relationship is as follows (These references are listed in <b><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496.s008" target="_blank">Text S1</a></b>): <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Cobb1" target="_blank">[3]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Bowen2" target="_blank">[7]</a><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Craig1" target="_blank">[1]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Hobson1" target="_blank">[8]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Worden1" target="_blank">[10]</a><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Shacklet1" target="_blank">[2]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Joussaume1" target="_blank">[9]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Noone1" target="_blank">[11]</a><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Cobb1" target="_blank">[3]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Hobson1" target="_blank">[8]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Worden1" target="_blank">[10]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Zhang1" target="_blank">[12]</a><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Benson1" target="_blank">[5]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Huete1" target="_blank">[13]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Peng1" target="_blank">[17]</a><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Epstein1" target="_blank">[18]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Wang1" target="_blank">[20]</a><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Bowen1" target="_blank">[6]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Jonsson1" target="_blank">[21]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-MendezBarroso1" target="_blank">[22]</a><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Huete1" target="_blank">[13]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Byrne1" target="_blank">[15]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-MendezBarroso1" target="_blank">[22]</a><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Wolfram1" target="_blank">[23]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045496#pone.0045496-Frankenberg1" target="_blank">[25]</a>.</p

The precipitation collection site.

<p>Thirteen precipitation collection sites along an elevation gradient in the eastern Taiwan.</p

The fine spatiotemporal scale predictability of the model.

<p>The predictability in continuous elevation and time data is shown. Using one-growing-season the iEVI-δ¹⁸O function at Taroko (91 m a.s.l.), Sinbaiyang (1676 m) and Siafongkuo (2876 m) and the δ¹⁸O-altitude relationship to predict the δ¹⁸O values along the elevation gradient and in other growing seasons.</p