To investigate the tropical Atlantic response to the remote El Nino-Southern
Oscillation (ENSO) forcing, a Reduced Physics  Coupled Global Circulation Model
(RP-CGCM) is developed, and four experiments are carried out. The results show that
the RP-CGCM is capable of capturing the major features of Tropical Atlantic Variability
(TAV) and its response to ENSO forcing.
The SST response to the remote influence of ENSO may be divided into two
stages. In stage one, the ENSO influences the tropical Atlantic SST primarily through
the Troposphere Temperature (TT) mechanism, which predicts a uniform warming in the
tropical Atlantic following the mature phase of El Nino. In the north tropical Atlantic
(NTA), the Walker mechanism and the Pacific-North-American (PNA) mechanism work
in concert with the TT-induced warming, giving rise to a robust SST response during the
boreal spring in this region. In the south tropical Atlantic (STA), the southeasterly wind
anomaly and increased stratus clouds work against the TT-induced warming, resulting in
a much weaker SST response in this region. At this stage, the response can be largely
explained by the ocean mixed layer response to changes in surface heat fluxes induced
by ENSO.
In stage two, ocean dynamics play a more active role in determining the
evolution of SST. The cross-equatorial wind anomaly in the western to central equatorial
Atlantic can change the SST in the eastern equatorial Atlantic through Bjerknes
feedback and the SST in the central equatorial Atlantic through Ekman feedback. These
feedback result in a cooling of SST in the equatorial south Atlantic (ESA) region which is so overwhelming that it cancels the warming effect induced by the TT mechanism and
reverses the sign of the warm SST anomaly that is formed during stage one in this
region.
In general, the horizontal advection of heat plays a secondary role in the SST
response to the remote influence of ENSO, except in the regions where the North
Equatorial Countercurrent (NECC) dominates and the SST variability is strong.
Entrainment is particularly important in maintaining the correct SST structure during
boreal summer.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/3841 |
| Date | 16 August 2006 |
| Creators | Fang, Yue |
| Contributors | Chang, Ping |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | 3696064 bytes, electronic, application/pdf, born digital |
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