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dc.contributor.authorChan, Johnny C.L.
dc.date.accessioned2015-07-31T17:55:20Z
dc.date.available2015-07-31T17:55:20Z
dc.date.issued1985-04
dc.identifier.citationMonthly Weather Review, Volume 113, pp. 599-606, April 1985.en_US
dc.identifier.urihttp://hdl.handle.net/10945/45699
dc.description.abstractThe interannual variations in tropical cyclone activity in the northwest Pacific (NWPAC) and their relationships with the EI Nino/Southern Oscillation (ENSO) phenomenon were studied using the method of spectral analyses. Time series of a Southern Oscillation Index (SOl, defined as the sea-level pressure difference between Easter Island and Darwin) and tropical cyclone activity in the entire (NWPAC) ocean basin as well as in different regions of the NWPAC were analyzed. Two spectral peaks are apparent in all these time series. One corresponds to the generally accepted Southern Oscillation with a period of - 3 to 3.5 years and another at the quasi-biennial oscillation (QBO) frequency. Cross-spectral analyses between the SOl and tropical cyclone activity show significant coherence in these two spectral peaks. The dominant peak is at the Southern Oscillation frequency with the SOl leading typhoon activity by almost a year. At the QBO frequency, the two series are almost in phase. Cyclone activity in the eastern part of NWPAC, however, is -180' out of phase with the SOl series at the Southern Oscillation frequency. It appears that fluctuations of cyclone activity at the dominant Southern Oscillation frequency may be explained in terms of the change in the horizontal and vertical circulations in the atmosphere during periods of low SOl. The establishment of an anomalous Walker Circulation shifts areas of enhanced or suppressed convection, leading to the observed variations in cyclone activity.en_US
dc.description.sponsorshipThe author, a National Research Council Research Associate during the period of this study, acknowledges support by the Foundation Research Program at the Naval Postgraduate School.en_US
dc.rightsThis publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. As such, it is in the public domain, and under the provisions of Title 17, United States Code, Section 105, may not be copyrighted.en_US
dc.titleTropical Cyclone Activity in the Northwest Pacific in Relation to the El Niño/Southern Oscillation Phenomenonen_US
dc.typeArticleen_US
dc.contributor.departmentMeteorologyen_US


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