HR: 0800h
AN: C51B-1035    [Abstracts]
TI: Estimation and Validation of \delta$^{18}$O Global Distribution with Rayleigh-type two Dimensional Isotope Circulation Model
AU: * Yoshimura, K
EM: kei@iis.u-tokyo.ac.jp
AF: Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo, 153-8505 Japan
AU: Oki, T
EM: taikan@iis.u-tokyo.ac.jp
AF: Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo, 153-8505 Japan
AU: Ohte, N
EM: nobu@bluemoon.kais.kyoto-u.ac.jp
AF: Kyoto University, Oiwake-cho, Kitashirakawa, Kyoto, 606-8502 Japan
AU: Kanae, S
EM: kanae@iis.u-tokyo.ac.jp
AF: Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo, 153-8505 Japan
AU: Kanae, S
EM: kanae@iis.u-tokyo.ac.jp
AF: Research Institute of Humanity and Nature, 335 Takashima-cho, Kyoto, 602-0878 Japan
AU: Ichiyanagi, K
EM: kimpei@jamstec.go.jp
AF: Frontier Observational Research System for Global Change, 3173-25, Showa-machi, Kanazawa-ku, Yokohama, 236-0001 Japan
AB: A simple water isotope circulation model on a global scale that includes a Rayleigh equation and the use of _grealistic_h external meteorological forcings estimates short-term variability of precipitation $^{18}$O. The results are validated by Global Network of Isotopes in Precipitation (GNIP) monthly observations and by daily observations at three sites in Thailand. This good agreement highlights the importance of large scale transport and mixing of vapor masses as a control factor for spatial and temporal variability of precipitation isotopes, rather than in-cloud micro processes. It also indicates the usefulness of the model and the isotopes observation databases for evaluation of two-dimensional atmospheric water circulation fields in forcing datasets. In this regard, two offline simulations for 1978-1993 with major reanalyses, i.e. NCEP and ERA15, were implemented, and the results show that, over Europe ERA15 better matched observations at both monthly and interannual time scales, mainly owing to better precipitation fields in ERA15, while in the tropics both produced similarly accurate isotopic fields. The isotope analyses diagnose accuracy of two-dimensional water circulation fields in datasets with a particular focus on precipitation processes.
DE: 1655 Water cycles (1836)
DE: 1833 Hydroclimatology
DE: 1854 Precipitation (3354)
DE: 1040 Isotopic composition/chemistry
DE: 0368 Troposphere--constituent transport and chemistry
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting