HR: 1340h
AN: H13E-0468    [Abstracts]
TI: Hydrologic Impacts of the Pacific Decadal Oscillation on ENSO Influenced Regions
AU: * Tootle, G
EM: tootleg@unlv.nevada.edu
AF: University of Nevada, Las Vegas, Department of Civil and Environmental Engineering 4505 Maryland Parkway Box 454015, Las Vegas, NV 89154-4015
AU: Piechota, T
EM: piechota@unlv.nevada.edu
AF: University of Nevada, Las Vegas, Department of Civil and Environmental Engineering 4505 Maryland Parkway Box 454015, Las Vegas, NV 89154-4015
AB: Several regions in the United States [Pacific Northwest (PNW), Southwest (SW), North Central (NC), Northeast (NE) and Gulf of Mexico (GM)] display a strong El Ni¤o-Southern Oscillation (ENSO) signal in which monthly precipitation (and resulting streamflow) vary in the winter-spring season following the onset of a summer season warm (El Ni¤o) or cold (La Ni¤a) phase of ENSO. Additionally, numerous studies have shown that in several of these regions (PNW, SW and GM), a distinct lag exists between the occurrence of a summer El Ni¤o (or La Ni¤a) and the resulting winter-spring streamflow variation. The concern for water planners is "how likely (probability) will winter-spring streamflow be above (or below) median if a summer season ENSO event occurs?" and, "can this probability be provided prior to the beginning of the water year (01 October)?" Research has shown that the Pacific Decadal Oscillation (PDO) can increase (or reduce) the effects of ENSO. PDO tends to oscillate with a characteristic period on the order of 50 years (a particular phase of the PDO will typically persist for about 25 years). This period differs greatly from ENSO events, which typically persist for 6 to 18 months. Water-year (October to September) average values of the PDO were examined for the period of 1941 to 2001. During this period, three distinct phases were observed: 1941 to 1961 (21 years - Declining), 1962 to 1987 (26 years - Rising) and 1988 to 2001 (14 years - Declining). Currently, we are in a Declining PDO phase, which should persist for approximately 10 more years. An additional concern for water planners is "will the current Declining PDO phase enhance or dampen a summer ENSO event?" Data was obtained for unimpaired streamflow stations in the PNW, SW and GM basins from 1942 to 2002 (61 years of data). Preliminary results in the SW basin reveal that the current Declining PDO phase does result in a higher likelihood of below median winter-spring streamflow, as a result of a summer La Ni¤a event (based on the Southern Oscillation Index), when compared to the Rising PDO phase.
DE: 1812 Drought
DE: 1833 Hydroclimatology
DE: 1860 Runoff and streamflow
DE: 1884 Water supply
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting