J. Atmos. Sci., 62, 3396-3407.
Adam H. Sobel
Department of Applied Physics and Applied Mathematics and Department of Earth and Environmental Sciences, Columbia University, New York, NY.
Suzana J. Camargo
IRI, Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY
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, 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
signals indicative of the El Ni\~no - 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, and 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 which
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 which 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.