HR: 1340h
AN: GC33A-1242    [Abstracts]
TI: Winter circulation anomalies in the western United States associated with antecedent season and interdecadal ENSO variability, 1948-1998
AU: * Brown, D P
EM: david.brown@unh.edu
AF: University of New Hampshire, Department of Geography 56 College Road, Durham, NH 03824 United States
AB: Many users of climate information across the western United States look to fall season conditions in the El Ni¤o-Southern Oscillation (ENSO) system as an indicator of potential winter season precipitation anomalies. In this study, the reliability of fall season ENSO conditions as a predictor of Western U.S. winter circulation anomalies associated with canonical precipitation impacts is shown to vary over multi-decadal time periods consistent with phasing of the Pacific Decadal Oscillation (PDO) pattern. During the PDO cold phase of 1948-1976, fall season El Ni¤o events tended not to precede the canonical winter troughing pattern over the West typically associated with above-normal precipitation in many areas, particularly the southwestern states. During the PDO warm phase of 1977-1998, fall season El Ni¤o conditions were more reliably associated with winter troughing, but typically only during moderate-to-strong El Ni¤o events. Fall season La Ni¤a conditions during both the cold and warm phases of the PDO generally correlated well with the occurrence of wintertime high-pressure ridging centered off the Pacific coast. The results presented here highlight uncertainty over multi-decadal time scales surrounding the use of fall ENSO conditions, particularly during El Ni¤o events, as a seasonal climate forecast tool for winter precipitation in the western United States.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1620 Climate dynamics (0429, 3309)
DE: 1630 Impacts of global change (1225)
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
SC: Global Climate Change [GC]
MN: Fall Meeting 2005