HR: 1340h
AN: B33A-0249    [Abstracts]
TI: Analysis of the global distribution of water isotopes in the NCAR atmospheric general circulation model
AU: * Lee, J
EM: jelee@atmos.berkeley.edu
AF: Department of Earth and Planetary Science, 307 McCone, University of California Berkeley, Berkeley, CA 94720 United States
AU: Fung, I
EM: inez@atmos.berkeley.edu
AF: Department of Earth and Planetary Science, 307 McCone, University of California Berkeley, Berkeley, CA 94720 United States
AU: DePaolo, D J
EM: depaolo@eps.berkeley.edu
AF: Department of Earth and Planetary Science, 307 McCone, University of California Berkeley, Berkeley, CA 94720 United States
AB: The cycling of water isotopes has been incorporated into the NCAR atmospheric general circulation model, CAM2. Isotope dynamics follow that of Jouzel et al. (1987) and other GCMs, with fractionation associated with evaporation at the surface as well as with cloud processes. The model yields a reasonable global pattern of water isotopes in precipitation; e.g., the „18O decreases as temperature increases, and it also decreases as precipitation amount increases. The latitudinal and vertical distribution of „18O in the atmospheric vapor is caused by the ratio of the condensation rate to the amount of vapor, with greater depletion at high latitudes and high altitudes. Over the ocean, the balance between precipitation and evaporation determines the isotopic composition of precipitation, with „18O less depleted where evaporation minus precipitation is high. This explains the "amount effect" of water isotopes. The role of land evapo-transpiration on the isotopic composition of vapor and precipitation will be discussed.
DE: 1655 Water cycles (1836)
DE: 1836 Hydrologic budget (1655)
DE: 1854 Precipitation (3354)
DE: 1040 Isotopic composition/chemistry
DE: 1615 Biogeochemical processes (4805)
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting