HR: 14:25h
AN: C43D-04    [Abstracts]
TI: Stable Isotopes In Precipitation: An Analysis Of GNIP Data And The Roles Of Temperature And Moisture Source In Isotope Distribution
AU: * Aggarwal, P K
EM: p.aggarwal@iaea.org
AF: Isotope Hydrology Section, IAEA, Wagramer Strasse 5, Vienna, A1400 Austria
AU: Alduchov, O A
EM: aoa@meteo.ru
AF: RIHMI-WDC, Korolev St., 6, Obninsk, 249020 Russian Federation
AU: Gourcy, L L
EM: l.gourcy@iaea.org
AF: Isotope Hydrology Section, IAEA, Wagramer Strasse 5, Vienna, A1400 Austria
AB: Arithmetic (unweighted) means of isotope ratios in 1960-2000 precipitation from nearly 410 stations of the IAEA/WMO's global network of isotopes in precipitation (GNIP) are described by the equation: d2H = 8.07(ñ 0.02) d18O + 9.9 (ñ 0.1) (n=3426; R2=0.98). Isotope data from 31 stations with a continuous record for 1960-2000 were evaluated for the periods 1960-1978, 1979-1987, and 1987-2000. Although the isotope relationships at these stations are slightly different than the global relationship based on all GNIP data, a discernible trend of isotope variations from 1961 to 2000 is absent. The temperature coefficient of d18O values is 0.82(ñ0.01) per oC for stations with a mean air temperature (MAT) range -20oC to -2oC, and 0.53(ñ0.01) per oC for stations with a MAT range of -20 to 0oC. These coefficients are slightly lower than those reported in previous reports based on a smaller data set. Tropical stations (MAT higher than about 18oC) do not show a temperature dependency or a consistent dependence on the amount of precipitation. An analysis of isotope data in the Asian Monsoon region (70 E - 160 W longitude) with air circulation and moisture transport patterns indicates that isotope distributions are controlled primarily by the moisture source in precipitation. Monthly isotope data from Vienna, Bangkok and Hong Kong were analyzed with respect to upper air parameters and moisture transfer patterns in the planetary boundary layer. These analyses provide a basis for understanding the primary control of temperature on isotopes in Vienna precipitation and of moisture source in Bangkok and Hongkong precipitations. A statistical analysis of horizontal variability based on the entire GNIP dataset indicates that a terrestrial network with about 980 stations distributed more or less uniformly over the globe would provide a strong basis for using the precipitation isotope compositions to study variations and changes in the hydrological cycle on an inter-annual or decadal scale.
DE: 1833 Hydroclimatology
DE: 1040 Isotopic composition/chemistry
DE: 1610 Atmosphere (0315, 0325)
DE: 1620 Climate dynamics (3309)
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting