HR: 11:50h
AN: H32B-07    [Abstracts]
TI: Trends in 20th century drought characteristics over the continental United States
AU: * Andreadis, K M
EM: kostas@hydro.washington.edu
AF: Civil and Environmental Engineering, University of Washington, Wilson Ceramic Lab, Box 352700, Seattle, WA 98195-2700 United States
AU: Lettenmaier, D P
EM: dennisl@u.washington.edu
AF: Civil and Environmental Engineering, University of Washington, Wilson Ceramic Lab, Box 352700, Seattle, WA 98195-2700 United States
AB: A simulated data set of hydroclimatalogical variables produced by the Variable Infiltration Capacity (VIC) macro-scale hydrology model, forced by a temporally-consistent long-term (1915-2003) meteorologic data set, is used to examine for potential trends in drought characteristics over the continental United States. The VIC model has been extensively validated over many continental scale river basins and various climates, and successfully used to reproduce a U.S. drought history for the same 1915-2003 period. Drought characteristics, such as intensity and duration, are estimated using gridded precipitation (forcings, directly related to observations), model-derived soil moisture, and model-derived runoff expressed as percentiles of the respective climatology at each model grid cell. Trend significance is determined using the non-parametric seasonal Mann-Kendall test on a monthly time-step. Different thresholds are used to examine droughts of varying severity (moderate to extreme), with the duration of an event defined as the number of months that soil moisture/runoff percentiles are below the threshold value. Trends in drought characteristics are examined in conjunction with trends in precipitation, soil moisture and streamflow data. In addition, streamflow data from the HCDN station network are used for verification of the trends found in the simulated runoff time series. The results show that there is a statistically significant increasing trend in both soil moisture and streamflow for the majority of the study domain on an annual basis, which generally corresponds to increasing trends in precipitation. Furthermore, examination of seasonal trends reveals strong spatial clustering of both wetting and drying trends. As a result, areas affected by drought appear to decrease in general. However, droughts have appeared to intensify in certain regions of the country. Drought durations, in general, do not show any significant trend over most of the domain. Finally, the association and consistency of the trends found in soil moisture and streamflow with precipitation and temperature signals is examined.
DE: 1812 Drought
DE: 1840 Hydrometeorology
DE: 1872 Time series analysis (3270, 4277, 4475)
SC: Hydrology [H]
MN: Fall Meeting 2005