HR: 16:50h
AN: GC52B-04    [PDF]
TI: Tree-Ring derived Ensemble Streamflow Reconstructions for the Gunnison River Basin
AU: * Webb, R S
EM: Robert.S.Webb@noaa.gov
AF: NOAA-CIRES Climate Diagnostics Center, 325 Broadway, Boulder, CO 80305 United States
AU: Woodhouse, C A
EM: Connie.Woodhouse@noaa.gov
AF: Paleoclimatology Program NOAA/NESDIS/NCDC, 325 Broadway, Boulder, CO 80305 United States
AB: Multicentury tree-ring records of hydroclimatic variability are now being considered in assessments of the regional risk of multiyear droughts and the expected occurrence interval of extreme drought. Critical questions being raised when tree-ring reconstructions are considered in the decision process focus on describing and quantifying uncertainty in the annual stream flow reconstructions. Potential sources of uncertainty in the reconstructions are: 1) measurement errors in both the instrumental data and the tree-ring data, and 2) model calibration errors due to the less than perfect relationship between tree-ring data and hydroclimatic variables. As an alternative to standard reconstruction approaches using a single "best" tree-ring calibration model, we use a suite of regression models to reconstruct each of five streamflow records in the Gunnison River Basin for the past 600 years. Our ensemble tree-ring reconstruction approach draws on the ensemble methodology used in operational weather and climate forecasting prediction. Application of an ensemble of regression models in tree-ring reconstructions of past hydroclimatic variability allows for a more realistic representation of uncertainty in the development and application of regression model relationships between tree-ring indices and hydroclimatic variability. The ensemble approach allows for the possibility that a suite of models based on a variety of calibration and independent verification periods can provide a more accurate representation of the past. While most individual regression model ensemble members explain less of the variance than the full period calibration model, the regression model ensemble mean provides a more robust reconstruction that includes an estimate of the uncertainty. A comparison of the recurrence interval of historically low flows in the Gunnison Basin estimated using our ensemble tree-ring reconstructions and using standard tree-ring reconstructions is used to illustrate the impact of including uncertainty in analyses.
DE: 1812 Drought
DE: 1860 Runoff and streamflow
DE: 1884 Water supply
DE: 3344 Paleoclimatology
SC: Global Climate Change [GC]
MN: 2003 Fall Meeting