Premium
Interannual variability of the tropical Atlantic independent of and associated with ENSO: Part I. The North Tropical Atlantic
Author(s) -
Handoh Itsuki C.,
Matthews Adrian J.,
Bigg Grant R.,
Stevens David P.
Publication year - 2006
Publication title -
international journal of climatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.58
H-Index - 166
eISSN - 1097-0088
pISSN - 0899-8418
DOI - 10.1002/joc.1343
Subject(s) - climatology , tropical atlantic , sea surface temperature , extratropical cyclone , forcing (mathematics) , el niño southern oscillation , atlantic multidecadal oscillation , environmental science , atlantic hurricane , atlantic equatorial mode , geology , tropical cyclone
The interannual variability of the tropical Atlantic ocean–atmosphere system is examined using 50 years of sea‐surface temperature (SST) and re‐analysis data, and satellite data when available. A singular value decomposition analysis of 12‐ to 72‐month bandpass filtered SST and zonal wind stress reveals two dominant modes of interannual variability. The SST anomalies are confined to the North Tropical Atlantic (NTA) in the first mode and extend over the equatorial and South Tropical Atlantic in the second mode. No evidence is found for an Atlantic SST dipole. The structure of the first (NTA) mode is examined in detail here, while the second mode has been described in a companion paper. In particular, the relationship of the NTA mode with El Niño–Southern Oscillation (ENSO) is investigated. There are 12 NTA events (seven warm and five cold) that are associated with ENSO, and 18 NTA events (seven warm and 11 cold) that are independent of ENSO. The ENSO‐associated NTA events appear to be a passive response to remote ENSO forcing, mainly via a Pacific‐North America (PNA)‐like wave train that induces SST anomalies over the NTA through changes in the surface wind and latent heat flux. The NTA anomalies peak four months after ENSO. There does not appear to be an atmospheric response to the NTA SST anomalies as convection over the Atlantic is suppressed by the anomalous Walker circulation due to ENSO. The ENSO‐independent NTA events also appear to be induced by an extratropical wave train from the Pacific sector (but one that is independent of Pacific SST), and forcing by the North Atlantic Oscillation (NAO) also contributes. As the event matures, the atmosphere does respond to the NTA SST anomalies, with enhanced convection over the Caribbean and a wave train that propagates northeastward to Europe. Copyright © 2006 Royal Meteorological Society