HR: 0830h
AN: B51E-1008    [PDF]
TI: Linking Water Flux Parameterisation Schemes to Isotopic Measurements in Basin-scale to Climate Models
AU: Dyer, L
EM: ldz@ansto.gov.au
AF: ANSTO Environment, PMB 1, Menai, NSW 2234 Australia
AU: Henderson-Sellers, A
EM: ahssec@ansto.gov.au
AF: ANSTO Environment, PMB 1, Menai, NSW 2234 Australia
AU: * McGuffie, K
EM: kendal.mcguffie@uts.edu.au
AF: Applied Physics, University of Technology, Sydney, Broadway, NSW 2007 Australia
AU: Noone, D
EM: dcn@caltech.edu
AF: Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 United States
AU: Irannejad, P
EM: pix@ansto.gov.au
AF: ANSTO Environment, PMB 1, Menai, NSW 2234 Australia
AB: Within the GEWEX (Global Energy and Water Cycle Experiment) Continental Scale Experiments (CSE) system, stable water isotope collection is co-coordinated by the International Atomic Energy Agency under its Global Network for Isotopes in Rivers (GNIR) and Global Network for Isotopes in Precipitation (GNIP). Simultaneous tracking of two isotopes in water (HDO and H$_2^{18}$O), makes it possible to trace the history of evaporative and condensation processes in the world's major river basins. Isotopic data from 1964 to 2000 show trends, possibly linked to land-use change impacts, at stations in the Andes, where as much as 88% of the Amazon's rainfall is shown (using isotopic measurements) to be derived from recycled moisture. We have compared twenty AMIP2 simulations for the CSEs with isotopic simulations from the Melbourne University GCM (MUGCM, Noone and Simmonds, 2002) which predicts the $^{18}$O and $^2$H concentrations in precipitation and atmospheric water vapor. Globally and in all the GEWEX regions, recent reanalyses products fail to conserve water because of soil moisture nudging and decreases in the soil moisture of more than 65% of the mean precipitation. VIC (Variable Infiltration Capacity) is found to conserve the surface water everywhere, providing reliable surface water simulations, when averaged over large areas and long periods of time (e.g. Nijssen {\it et al.}, 2001). Overall, we find that MUGCM generates surface water budget components for the GEWEX CSEs that match observations, including VIC, better than many AMIP2 models. For example, in the Murray Darling basin, an area poorly simulated by many AGCMs, the evaporation to precipitation ratio is 0.92 from observations, 0.86 in VIC and 0.98 when the AMIP2 AGCMS are averaged. For the runoff to precipitation ratio, these values are 0.08 from observations, 0.14 from VIC and 0.09 for the AMIP2 average. We find that MUGCM (generating 0.79 for E/P and 0.21 for R/P) behaves as well as the best performing land-surface schemes, the \lq SiB-lings', but possibly for \lq wrong' reasons, which are explained.
DE: 0315 Biosphere/atmosphere interactions
DE: 0322 Constituent sources and sinks
SC: Biogeosciences [B]
MN: 2003 Fall Meeting