Abstract
AbstractThe deuterium excess (d‐excess) and more recently developed 17O excess (Δ′17O) of precipitation are isotopic tracers that are sensitive to oceanic moisture source (OMS) conditions. However, other regional and local processes also affect precipitation d‐excess and Δ′17O and may modify or overprint their OMS signals. Here, I leverage the new atmospheric moisture flow data set to diagnose the OMS regions and conditions globally and show that OMS temperature and relative humidity together explain 41% of the variability in monthly mean precipitation d‐excess in low‐ and mid‐latitudes. Based on a few sites currently having paired d‐excess and Δ′17O data, I also show that the contrasting sensitivity between d‐excess and Δ′17O to OMS temperature, which is initially predicted by theory, is distinguishable from precipitation observations under annual mean conditions. This study contributes to disentangling the complex controls on precipitation d‐excess and Δ′17O by quantifying the crucial role of OMS dynamics.
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