Intraseasonal Variability of δ18O of Precipitation in The Indonesia Maritime Continent

Abstract:

The Indonesian maritime continent (IMC) consists of many islands in a warm pool of sea water and is located between two great oceans—the Pacific Ocean and Indian Ocean, and two major continents—the Asian and Australian continents. This tropical region also influenced by many regional and local climate and weather phenomenon which causes high spatial and temporal rainfall variability. These factors may produce unique variability of isotopic precipitation. The isotopic content (d¹⁸O and dD) in precipitation have been known to have important role for reconstructing the atmospheric circulation, hydrological cycle, and paleoclimate.

Using daily data from six observation station across the IMC (Bukit tinggi, Jambi, Denpasar, Makasar, Manado, and Palau Island), the variability of δ¹⁸O was explored. Observation times for each station were different. Bukit Tinggi (GAW) was from Jan. 2001 – Mar. 2010, Jambi (JMB) was from Apr. 2001 – Dec. 2005, Denpasar (DPS), Makassar (MKS), Manado (MND) were from Nov. 2002 – Mar. 2010, and Palau Island (PLL) was from Dec. 2001 – May 2007. Daily average value of δ¹⁸O were -7.57‰, -5.41‰, -3.15‰, -6.12‰, -5.49‰ and -4.26‰ for GAW, JMB, DPS, MKS, MND and PLL respectively. Daily value of δ¹⁸O in GAW has the lowest value compare with the other station was because the location of GAW station located at high altitude.

High correlation of variability of δ¹⁸O and Madden-Julian Oscillation (MJO) was observed at western part of the IMC (GAW and JMB), and northern part of the IMC (MKS, MND, and PLL), meanwhile δ¹⁸O variability at DPS was less correlated with MJO compare with other stations.

Preliminary result from Color Moisture Analysis (CMA) model revealed that precipitable water at GAW and JMB stations was mostly occupied by water vapor evaporated from the Indian Ocean. However, precipitable water at other stations was mostly composed of water vapor evaporated from the Java Sea and the Pacific Ocean. These findings indicate that water vapor evaporated from the Indian Ocean related to the MJO can only reach the Island of Sumatra in the western part of the IMC. Then, Indian Ocean origin was replaced by the water vapor evaporated from the Java Sea and the Pacific Ocean.