We present precipitation isotope data (δ2H and δ18O values) from 19 stations across the tropics collected from 2012 to 2017 under the Coordinated Research Project F31004 sponsored by the International Atomic Energy Agency. Rainfall samples were collected daily and analysed for stable isotopic ratios of oxygen and hydrogen by participating laboratories following a common analytical framework. We also calculated daily mean stratiform rainfall area fractions around each station over an area of 5° x 5° longitude/latitude based on TRMM/GPM satellite data. Isotope time series, along with information on rainfall amount and stratiform/convective proportions provide a valuable tool for rainfall characterisation and to improve the ability of isotope-enabled Global Circulation Models to predict variability and availability of inputs to fresh water resources across the tropics.
Time series of cave drip water oxygen isotopes (δ18O) provide site‐specific assessments of the contributions of climate and karst processes to stalagmite δ18O records employed for hydroclimate reconstructions. We present ~12‐year‐long time series of biweekly cave drip water δ18O variations from three sites as well as a daily resolved local rainfall δ18O record from Gunung Mulu National Park in northern Borneo. Drip water δ18O variations closely match rainfall δ18O variations averaged over the preceding 3–18 months. We observe coherent interannual drip water δ18O variability of ~3‰ to 5‰ related to the El Niño–Southern Oscillation (ENSO), with sustained positive rainfall and drip water δ18O anomalies observed during the 2015/2016 El Niño. Evidence of nonlinear behavior at one of three drip water monitoring sites implies a time‐varying contribution from a longer‐term reservoir. Our results suggest that well‐replicated, high‐resolution stalagmite δ18O reconstructions from Mulu could characterize past ENSO‐related variability in regional hydroclimate.
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