Observational Research on Stable Isotopes in Precipitation over Indonesian Maritime Continent

Abstract

The Indonesian Maritime Continent (IMC) is located in the tropics and consists of a number of islands and seas. This particular arrangement of land masses and seas produces unique weather and climate characteristics. Various hydrometeorolo- gy studies have been conducted exploring the variability of stable isotopes in precip- itation over the IMC. Stable isotopes (δ18O and δD) in precipitation can be used to obtain information about atmospheric processes (e.g., precipitation, temperature and hydrological cycle). The Global Network of Isotopes in Precipitation, operated by the International Atomic Energy Agency, has been conducting worldwide month- ly surveys of isotope levels in precipitation since 1961. To better understand the iso- topic variability in the IMC, the Japan Agency for Marine-Earth Science and Tech- nology began operating in the IMC region in 2001. There are three types of seasonal variation of stable isotopes in precipitation, depending on the level of precipitation amount and also stable isotopic value, namely, semiannual, anti-monsoonal and monsoonal. Negative correlations between the precipitation amount and stable iso- tope value (amount effect) were identified when using the monthly averages. The in- terannual variability of stable isotopes in precipitation was mainly because of El Niño Southern Oscillation activity, whereas intraseasonal variability was closely re- lated to the Madden-Julian Oscillation. Stable isotope variability in short periods was found to be due to precipitation cloud types and post-condensation processes.