HR: 16:48h
AN: A24A-05    [Abstracts]
TI: Storm Track Analysis from CCSM3: Present and Future Climate
AU: * Teng, H
EM: hteng@ucar.edu
AF: NCAR, 1850 Table Mesa Drive, Boulder, CO 80305,
AU: Washington, W
EM: wmw@ucar.edu
AF: NCAR, 1850 Table Mesa Drive, Boulder, CO 80305,
AU: Meehl, G
EM: meehl@ucar.edu
AF: NCAR, 1850 Table Mesa Drive, Boulder, CO 80305,
AB: Climatology and interannual variations of wintertime extratropical cyclone frequency in CCSM3 20th-century simulation are compared with the NCEP/NCAR reanalysis during 1950-1999. CCSM3 can simulate the storm tracks reasonably well, although the model produces slightly less cyclones at the beginning of the Pacific and Atlantic storm tracks and weaker poleward deflection over the Pacific. As in the reanalysis, frequency of cyclones stronger than 980 hPa shows significant correlation with the Pacific/North America (PNA) teleconnection pattern over the Pacific region and with the North Atlantic Oscillation (NAO) in the Atlantic sector. Composite maps are constructed for opposite phases of El Nino-Southern Oscillation (ENSO) and the NAO and all anomalous patterns coincide with observed. One CCSM3 21st-century A1B scenario realization indicates there is significant increase in the extratropical cyclone frequency on the US west coast and decrease in Alaska. Meanwhile, cyclone frequency increases from the Great Lakes region to Quebec and decreases over the US east coast, suggesting a possible northward shift of the Atlantic storm tracks under the warmer climate. The cyclone frequency anomalies are closely linked to changes in seasonal mean states of the upper-troposphere zonal wind and baroclinicity in the lower troposphere. Due to lack of 6-hourly outputs, we cannot apply the cyclone tracking algorithm to the other 8 CCSM3 realizations. Based on the linkage between the mean state change and the cyclone frequency anomalies, it is likely a common feature among the other ensemble members that cyclone activity is reduced on the East Coast and in Alaska as a result of global warming.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1626 Global climate models (3337, 4928)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting