HR: 14:55h
AN: A33B-06    [Abstracts]
TI: The Relationship Between ENSO and Typhoon Activity
AU: * Camargo, S J
EM: suzana@iri.columbia.edu
AF: International Research Institute for Climate Prediction, The Earth Institute of Columbia University, PO Box 1000, Lamont Campus, Palisades, NY 10964-8000 United States
AU: Sobel, A H
EM: ahs129@columbia.edu
AF: International Research Institute for Climate Prediction, The Earth Institute of Columbia University, PO Box 1000, Lamont Campus, Palisades, NY 10964-8000 United States
AU: Sobel, A H
EM: ahs129@columbia.edu
AF: Department of Applied Physics and Applied Mathematics, Department of Earth and Environmental Sciences, Columbia University, 500 West 120th St., Rm. 217, New York, NY 10027 United States
AB: The influence of the El Ni\~no - Southern Oscillation (ENSO) on tropical cyclone intensity in the Western North Pacific basin is examined in interannual and shorter time scales. An index of TC activity [accumulated cyclone energy (ACE)] is used, which is shown to be positively correlated with ENSO indices. There is a tendency in El Ni\~no years towards tropical cyclones which are both more intense and longer-lived than in La Ni\~na years. The relationship is consistent over the annual cycle of tropical cyclone activity, and ACE during the peak season (northern summer and fall) is correlated approximately as strongly with ENSO indices up to six months later (northern winter) as simultaneously. The lifetime and intensity effects both contribute significantly to the ENSO signal in ACE, though the lifetime effect appears to be slightly more important. The influence of western north Pacific (WNP) tropical cyclones (TCs)on their large-scale environment is also examined by lag-regressing various large-scale climate variables on ACE on a weekly time scale. At all leads and lags out to several months, persistent, slowly evolving signals indicative of the El Nino - Southern Oscillation (ENSO) phenomenon are seen in all the variables, reflecting the known seasonal relationship of TCs in the WNP to ENSO. Superimposed on this are more rapidly evolving signals, at leads and lags of one or two weeks, directly associated with the TCs themselves. In the same region, lagging ACE by a week or two and so presumably reflecting the influence of TCs on the local environment, signals are found which might be expected to negatively influence the environment for later cyclogenesis, and thus to play a role in regulating the total annual number of TCs in the basin, which has very little interannual variability. On the same short time scale, an increase in equatorial SST near and east of the date line is seen, presumably associated with equatorial surface westerly anomalies that are also found. This, combined with the correlation between ACE and ENSO indices on the seasonal time scale, suggests the possibility that TCs may play an active role in ENSO dynamics.
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 3374 Tropical meteorology
DE: 4522 El Ni¤o
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting