HR: 1340h
AN: GC33A-1241    [Abstracts]
TI: Sensitivity of Spring-Summer Drought to Warming in Montane and Arid Regions of The Western US
AU: * Hidalgo, H G
EM: hhidalgo@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive, MC 0224, La Jolla, CA 92093 United States
AU: Cayan, D R
EM: dcayan@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive, MC 0224, La Jolla, CA 92093 United States
AU: Dettinger, M D
EM: mdettinger@ucsd.edu
AF: United States Geological Survey / SIO, 9500 Gilman Drive, MC 0224, La Jolla, CA 92093
AB: Soil moisture and actual evapotranspiration (AET) simulated by the Variable Infiltration Capacity (VIC) model provide informative depictions of the historical variations of spring-summer drought conditions and their connections with winter preciptiation in montane and arid regions of the western US. Analysis of such simulations provides a basis for better understanding the determinants of warm-season drought, and comparisons of simulated drought conditions with warm-season observations of satellite-derived Normalized Vegetation Difference Indices (NVDI) helps confirm those conclusions, especially in the arid zones. In certain parts of the montane regions, sufficient water is usually available during spring and early summer, as runoff and soil moisture remnants of winter snowpacks, so that AET rates are limited primarily by the energy available. In these regions, spring-summer drought is most sensitive totemperature (T). In arid regions, T is not as significant a determinant of spring-summer drought and AET rates depend on water availability from both winter and warm-season precipitation. Winter precipitation can be an important determinant of spring-summer drought in the montane regions, but essentially always is the primary determinant in semi-arid to arid regions. In the lowlands, correlations between winter precipitation and soil moisture are very strong at lags of three months, although in some regions like southern California, significant correlations were found as lags of five months. In montane regions, the storage of winter precipitation in the natural reservoirs provided by snowpack adds extra lags of land memory to those provided by soil moisture storage. In these regions, the strongest correlations were found between DJF precipitation and MJJ soil moisture (lag five months). In this context, warming trends in the montane regions of the western US may be expected to result in wetter than historical soils during winter and early spring (due to larger rain/snow ratios and earlier snowmelt) and drier conditions during late spring and summer (due to increased AET rates).
DE: 1630 Impacts of global change (1225)
DE: 1809 Desertification
DE: 1812 Drought
DE: 1818 Evapotranspiration
DE: 1836 Hydrological cycles and budgets (1218, 1655)
SC: Global Climate Change [GC]
MN: Fall Meeting 2005