Recent advancements in analytical techniques and instruments make it possible to use 17O-excess as a new tracer in hydrological studies. However, observations show that controls of 17O-excess are much more complicated than experiments and theory suggested. Further investigation is needed to understand what controls the variability of 17O-excess, particularly in the tropics, where studies in 17O-excess are sparse. During this MOE Tier 2 project, we will collect daily precipitation samples from our regional network of rain stations in Southeast (SE) Asia, and analyze them for stable isotopes, including d18O, d2H (dD), d17O, and the secondary parameters d-excess and 17O-excess. Our observations will be further compared with the simulations from two different isotope-enabled GCMs. The objectives of this research are: (1) to investigate the spatial-temporal variations in stable isotopes of precipitation in SE Asia; (2) to identify the major atmospheric and climate processes (e.g., ENSO, MJO, IOD and monsoons) that drive these variations, with a special focus on the change in 17O-excess; (3) to examine the correlation between 17O-excess and relative humidity (RH) in moisture source regions; and (4) to explore how microphysics during tropical convection affect stable isotope signals, specifically 17O-excess. Our study will help to improve the physical and chemical components of isotope-enabled GCMs, particularly those incorporating d17O and 17O-excess, and ultimately improve our prediction of the future distribution of precipitation and thus freshwater in SE Asia, where water resources and food security are highly vulnerable to climate change.

Funding Sources:

  • Earth Observatory of Singapore
  • Ministry of Education, Singapore

Project Years:

2020 to 2023

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The Team

HE Shaoneng River

HE Shaoneng River

Principal Research Fellow

WANG Xianfeng

WANG Xianfeng

Principal Investigator



PhD Student


Nathalie Goodkin, American Museum of Natural History 

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