1. ENSO and its impact on eastern/southern African climate:
the large-scale view
Alessandra Giannini (IRI)

2. Outline:
ENSO theory
ENSO monitoring
ENSO impact on eastern/southern Africa
The dynamics of the ENSO teleconnection

3. ENSO theory - a coupled ocean/atmosphere system
Bjerknes (1969), reviewed in Neelin et al., “ENSO theory”, in J. Geophys. Res. (1998)

4. ENSO theory - a coupled ocean/atmosphere system
Delayed Oscillator theory:
Schopf, PF and MJ Suarez, “Vacillations in a coupled ocean-atmosphere
model”, J. Atmos. Sci., 45,
Battisti, DS and AC Hirst, “Interannual variability in the tropical
atmosphere/ocean system: influence of the basic state, ocean geometry and
nonlinearity” J. Atmos. Sci., 46,
all reviewed in Neelin et al., “ENSO theory”, J Geophys Res,
103(C7),
2 characterizations of the ENSO system:
non-linear, quasi-periodic
linear, stochastically forced
and their consequence for predictability

5. ENSO monitoring

6. ENSO impact

7. ENSO impact
Ropelewski and Halpert, “Global and regional precipitation patterns associated with the El Nino-Southern Oscillation”, Mon Wea Rev, 115,

8. The ENSO teleconnection:
Chiang, JCH and AH Sobel, “Tropical tropospheric temperature variations
caused by ENSO and their influence on the remote tropical climate”, J. Climate, 15,
- atmospheric anomalies, i.e. the “atmospheric bridge”:
global (e.g. tropospheric temperature, 200hPa height...)
and regional (e.g. near-surface winds, precipitation...)
- delayed response of the remote oceans
local thermodynamic response,
response to ENSO-related anomalies in near-surface winds...

9. Goddard, L and NE Graham, “Importance of the Indian Ocean for simulating rainfall anomalies over eastern and southern Africa”, J Geophys Res, 104,

10. atmospheric
adjustment:
net surface
heat fluxes
El Nino – central equatorial Pacific
global warming – global tropical oceans
(e.g. Neelin et al., GRL 2003)
What role for the
land surface??
(e.g. Chiang and Lintner,
J. Climate 2005)

11. Chiang and Sobel, J Climate 2002
(Yulaeva and Wallace , J Climate 1994)

12. NCEP-NCAR
Reanalysis
200 hPa height
sfc temp
Kaplan SSTa

13. Year (0) of a warm ENSO Year (1) of a warm ENSO
Indeje, M et al., “ENSO signals in East African rainfall seasons”. Int. J. Climatology, 20, 19-46

14. January-March 1992 v. January-March 1998
Reason, CJC and D Jagadheesha, “A model investigation of recent ENSO impacts over
southern Africa”. Meteorol. Atmos. Phys., 89,

15. Conclusions:
we have sensible theories for how the coupled ocean-atmosphere ENSO system works, and for its impact on the global climate
these theories can guide our expectations related to prediction of ENSO and its general impacts, BUT knowledge of the regional climate system, and understanding of its interaction with global climate anomalies is critical to predict regional impacts.