HR: 1340h
AN: U53A-0705    [Abstracts]
TI: Uncertainty in Projections of Impacts of Climate Change on Sierra Nevada mountain hydrology in California
AU: * Maurer, E P
EM: emaurer@engr.scu.edu
AF: Santa Clara University Civil Engineering Department, 500 El Camino Real, Santa Clara, CA 95053-0563 United States
AU: Duffy, P B
EM: pduffy@llnl.gov
AF: Lawrence Livermore National Laboratory Climate and Carbon Cycle Modeling Group, Atmospheric Sciences Division, Livermore, CA 94551-0808 United States
AB: Understanding the uncertainty in the projected impacts of climate change on California's Sierra Nevada hydrology will clarify where hydrologic impacts can be expected with higher confidence, and will help address scientific questions related to possible improvements in climate modeling. In this study, we focus on California, a region that is vulnerable to hydrologic impacts of climate change. We statistically bias correct and downscale the monthly temperature and precipitation projections from 10 global climate models (GCMs) from the Coupled Model Intercomparison Project. These GCM simulations include both a control period (with unchanging CO2 and other atmospheric forcing) and a perturbed period with a 1-percent per year increase in CO2 concentration. We force a distributed hydrologic model with bias-corrected and statistically downscaled GCM data, and generate streamflow at strategic points in the Sacramento-San Joaquin River basin. Among our findings are that inter-model variability does not prevent significant detection of decreases in summer low flows, increases in winter flows or the shifting of flow to earlier in the year. Uncertainty due to sampling of a 20-year period in an extended GCM simulation accounts for the majority of inter-model variability for summer and fall months, while varying GCM responses to temperature and precipitation forcing add to the variability in the winter. Inter-model variation in projected precipitation accounts for most of the uncertainty in winter and spring flow increases in both the North and South regions, with a greater influence in the North. The influence of inter-model precipitation variability on May-September streamflow decreases in later years, as higher temperatures dominate the hydrologic response, and melting snowpack has less influence.
DE: 1655 Water cycles (1836)
DE: 1833 Hydroclimatology
DE: 1860 Runoff and streamflow
DE: 1863 Snow and ice (1827)
SC: Union [U]
MN: 2004 AGU Fall Meeting