HR: 17:45h
AN: H22I-08    [PDF]
TI: Murray Darling Basin Isotope Observations: an Essential Component of the Australian CEOP
AU: Stone, D
EM: David.Stone@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: Department of Applied Physics, University of Technology, Sydney, Broadway, NSW 2007 Australia
AU: Bradd, J
EM: John.Bradd@ansto.gov.au
AF: ANSTO Environment, PMB 1, Menai, NSW 2234 Australia
AU: Airey, P
EM: Peter.Airey@ansto.gov.au
AF: ANSTO Environment, PMB 1, Menai, NSW 2234 Australia
AB: The Murray Darling Basin Coordinated Enhanced Observing Period (CEOP) is the Australian contribution to the international effort by the World Climate Research Program (WCRP) to acquire in situ and satellite hydrometeorological data and to use these data sets to develop improved land surface process understanding in climate models. Within the GEWEX Continental Scale Experiments (CSE) system, the Murray Darling Basin (MDB) isotope collection is also co- coordinated with the International Atomic Energy Agency's Global Network for Isotopes in Rivers (GNIR). The data collection phase extends from 1 July 2002 to 30 June 2005 with a special focus on Darling River in situ reference sites. We are using CEOP data to monitor water and salt processes and to improve their representation in various atmosphere and land surface hydrometeorological models. Specifically, we find that among the 17 AMIP (Atmospheric Model Intercomparison Project) II AGCMs (Atmospheric General Circulation Models) with no reporting errors (Henderson-Sellers {\it et al.}, 2003) six fail to close the water balance to within $\pm$0.05 mm d$^{-1}$ in the Murray Darling CSE. Also seven models implausibly simulate 17-year mean evaporation greater than mean precipitation in the MDB due, to some extent, to poor soil water initialisation. Indeed, we find that soil water initialisation is a prevalent problem in all the GEWEX CSE regions. Furthermore, the non-closure of their surface water budget and very different evaporation ratios from observations suggest that reanalyses are not appropriate tools for evaluating the AGCMs' simulated surface water budget components. Due to constrained atmospheric forcing, off-line land-surface schemes, such as VIC, close the surface water balance and simulate evaporation ratios better than any reanalyses but in some regions, such as the MDB, runoff ratios are very different from observations. Here, we report on simulated and observed surface water budget components from models and reanalyses. Finally, we examine isotopes as an alternative tool for the evaluation of AGCMs' hydrometeorology.
DE: 0315 Biosphere/atmosphere interactions
DE: 0322 Constituent sources and sinks
SC: Hydrology [H]
MN: 2003 Fall Meeting