HR: 1340h
AN: A53B-0879    [Abstracts]
TI: Regional Climate and Hydrological Responses to El Nino in an Increased CO$_2$ Climate
AU: * Gibbard, S G
EM: gibbard1@llnl.gov
AF: Lawrence Livermore National Laboratory, P.O. Box 808 L-413, Livermore, CA 94550 United States
AU: Maurer, E
EM: emaurer@engr.scu.edu
AF: Santa Clara University, Civil Engineering Department, Santa Clara, CA 95053 United States
AU: Duffy, P B
EM: duffy2@llnl.gov
AF: Lawrence Livermore National Laboratory, P.O. Box 808 L-413, Livermore, CA 94550 United States
AB: Much of California typically experiences above-average precipitation amounts during El Nino (warm-phase ENSO) events. We would like to know if similar precipitation anomalies will occur in an increased greenhouse gas climate, and what corresponding river flow rates will be given that a smaller proportion of precipitation will be snow in the future than at present. The effects of increased atmospheric CO$_2$ on the frequency and amplitude of the ENSO phenomenon-as measured by anomalies in sea surface temperatures (SSTs)-are not known. However, we can use models to assess precipitation and other hydrological responses to ENSO under the assumption that the amplitude of ENSO will be unaffected by increased greenhouse gases. We performed an ensemble of simulations of global climate with a high-resolution model of the atmosphere forced with prescribed monthly-mean SSTs representing El Nino conditions in an increased CO$_2$ climate. These SSTs consist of observed climatological SSTs + a simulated SST response to doubled atmospheric CO$_2$ + observed SST anomalies for the winter 1997-1998 (the most recent strong El Nino). A 10-year control simulation of the present climate (forced by climatological observed SSTs) was also performed. After bias correction and statistical downscaling, results from the atmospheric model were used to drive a spatially resolved surface hydrology model configured for major watersheds in California. We assess precipitation rates and river flow rates in increased CO$_2$ El Nino conditions, and compare them to those in present-climate El Nino and increased CO$_2$ normal-year conditions.
DE: 4522 El Ni¤o
DE: 1655 Water cycles (1836)
DE: 1854 Precipitation (3354)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting