Validation of Changing Water Origins over Indochina during the Withdrawal of the Asian Monsoon using Stable Isotopes

  • Ichiyanagi Kimpei
    Institute of Observational Research for Global Change (IORGC), Japan Agency for Marine-Earth Science and Technology
  • Yoshimura Kei
    Institute of Industrial Science, The University of Tokyo
  • Yamanaka Manabu D.
    IORGC/Graduate School of Science and Technology, Kobe University

Abstract

Daily rainfall and δ18O were observed from August to November 2001 at three stations in Thailand. Water origins were estimated using a tagged-water transport model. The temporal and spatial distributions of water origins showed a clear transition from the Indian Ocean to the Pacific Ocean as the Asian monsoon retreated from Indochina. A new definition of the withdrawal date of the Asian monsoon over Indochina is proposed that considers the transition of the origin of water vapor. The daily variability of precipitation isotopes at three stations in Thailand was reproduced at statistically significant levels using a Rayleigh-type isotope circulation model. Therefore, the atmospheric water balance in the model can be validated reliably with these precipitation isotopes. Nevertheless, the simulated δ18O values were obviously underestimated, perhaps because of uncertainties in the evaporating isotope ratios and the lack of isotope physics at small scales.

Journal

  • SOLA

    SOLA 1 (0), 113-116, 2005

    Meteorological Society of Japan

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