TITLE:
The Energy Cycle Associated to the Pacific Walker Circulation and Its Relationship to ENSO
AUTHORS:
José Augusto P. Veiga, Alexandre B. Pezza, Tercio Ambrizzi, V. Brahmananda Rao, Sergio H. Franchito, Marcos C. Yoshida
KEYWORDS:
Walker Circulation; Energetics; El Nino; La Nina; ENSO
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.3 No.4,
October
31,
2013
ABSTRACT:
In this paper we study the Lorenz
energy cycle of the Walker circulation associated with ENSO. The robust
formulation of the energetics allows drawing a clear picture of the global
energy and conversion terms associated with the three dimensional domains appropriate to qualify the large
scale transfers that influence, and are influenced by, the anomalies during
ENSO. A clear picture has emerged in that El Nino and La Nina years have
approximately opposite anomalous energy fluxes, regardless of a non-linear
response identified in the potential energy fields (zonal and eddy). During El
Ninos the tropical atmosphere is characterized by an increase of zonal available potential
energy, decrease of eddy available potential energy and decrease of kinetic energy
fields. This results in weaker upper level jets and a slowingdown of the
overall Walker cell. During La Ninas reversed conditions are triggered, with an
acceleration of the Walker cell as observed from the positive anomalous kinetic
energy. The potential energy in the Walker circulation domain during the cold
phase is also reduced. An equally opposite behavior is also experienced by the energy conversion
terms according to the ENSO phase. The energetics-anomalous behavior seem to be
triggered at about the same time when ENSO starts to manifest for both the
positive and negative phases, suggesting a coupled mechanism in which
atmospheric and oceanic anomalies interact and feed back onto each other.