Influence of western North Pacific tropical cyclones on their large-scale environment

Publication Type  Journal Article
Year of Publication  2005
Authors  Sobel, A. H.; Camargo, S. J.
Journal Title  Journal of the Atmospheric Sciences
Volume  62
Issue  9
Pages  3396-3407
Journal Date  Sep
ISBN Number  0022-4928
Accession Number  ISI:000232275300023
Key Words  madden-julian oscillation; el-nino; southern oscillation; equatorial pacific; wind bursts; enso; cyclogenesis; intensity; oceans; perspective

The authors investigate the influence of western North Pacific (WNP) tropical cyclones (TCs) on their large-scale environment by lag regressing various large-scale climate variables [atmospheric temperature, winds, relative vorticity, outgoing longwave radiation (OLR), column water vapor, and sea surface temperature (SST)] on an index of TC activity [accumulated cyclone energy (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. These include anomalies of positive low-level vorticity, negative OLR, and high column water vapor associated with anomalously positive ACE, found in the region where TCs most commonly form and develop. 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 that might be expected to negatively influence the environment for later cyclogenesis. These signals include an SST reduction in the primary region of TC activity, and a reduction in column water vapor, and increase in OLR that may or may not be a result of the SST reduction.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.


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