HR: 16:30h
AN: H54A-03    [Abstracts]
TI: Tropical intraseasonal variabilitiy and extreme flooding in California: The New Year's 1997 Floods
AU: * Galewsky, J
EM: jg2282@columbia.edu
AF: Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10027 United States
AU: Sobel, A H
EM: ahs129@columbia.edu
AF: Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10027 United States
AB: Recent studies have linked California wintertime floods to tropical intraseasonal variability. Statistically significant links have been established between the Madden-Julian Oscillation (MJO) and extreme precipitation events in California. The anamolous moisture transport associated with these events is often referred to as the "Pineapple Express" because much of the moisture flows over the Hawaiian Islands en route to the West Coast. The destructive floods that affected much of California during January 1997 were an example of a Pineapple Express type system. We present a meteorological case study of this event using numerical simulations computed with the Fifth Generation PSU/NCAR Mesoscale Model (MM5). Our results indicate that the topography of the Sierra Nevada and Coast Ranges exerted primary control over the localization of extreme rainfall and the associated geomorphic effects. Moisture-laden winds were able to flow over mountainous topography and release copious rainfall over the northern Coast Ranges and northern Sierra Nevada, while drier winds were deflected by topography and acted to enhance rainfall in the northern Sierras by changing the effective topography of the western Sierra Nevada foothills. The strong coupling between topography and extreme rainfall in this case suggests a range of potentially important feedbacks that may have shaped California's landscape.
DE: 1821 Floods
DE: 1824 Geomorphology (1625)
DE: 1833 Hydroclimatology
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting