Paper No. 99118 of the Journal of the American Water Resources Association.Discussions are open until December 1, 2000.
A COMPARISON OF DELTA CHANGE AND DOWNSCALED GCM SCENARIOS FOR THREE MOUNFAINOUS BASINS IN THE UNITED STATES1
Article first published online: 8 JUN 2007
JAWRA Journal of the American Water Resources Association
Volume 36, Issue 2, pages 387–397, April 2000
How to Cite
Hay, L. E., Wilby, R. L. and Leavesley, G. H. (2000), A COMPARISON OF DELTA CHANGE AND DOWNSCALED GCM SCENARIOS FOR THREE MOUNFAINOUS BASINS IN THE UNITED STATES. JAWRA Journal of the American Water Resources Association, 36: 387–397. doi: 10.1111/j.1752-1688.2000.tb04276.x
- Issue published online: 8 JUN 2007
- Article first published online: 8 JUN 2007
- climate change;
- precipitation-runoff modeling;
- General Circulation Model;
- surface water hydrology
ABSTRACT: Simulated daily precipitation, temperature, and runoff time series were compared in three mountainous basins in the United States: (1) the Animas River basin in Colorado, (2) the East Fork of the Carson River basin in Nevada and California, and (3) the Cle Elum River basin in Washington State. Two methods of climate scenario generation were compared: delta change and statistical downscaling. The delta change method uses differences between simulated current and future climate conditions from the Hadley Centre for Climate Prediction and Research (HadCM2) General Circulation Model (GCM) added to observed time series of climate variables. A statistical downscaling (SDS) model was developed for each basin using station data and output from the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEPINCAR) reanalysis regridded to the scale of HadCM2. The SDS model was then used to simulate local climate variables using HadCM2 output for current and future conditions. Surface climate variables from each scenario were used in a precipitation-runoff model. Results from this study show that, in the basins tested, a precipitation-runoff model can simulate realistic runoff series for current conditions using statistically down-scaled NCEP output. But, use of downscaled HadCM2 output for current or future climate assessments are questionable because the GCM does not produce accurate estimates of the surface variables needed for runoff in these regions. Given the uncertainties in the GCMs ability to simulate current conditions based on either the delta change or downscaling approaches, future climate assessments based on either of these approaches must be treated with caution.