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Sensitivity of monsoon variability / predictability
to SST forcing - WP1200
Partners involved: UREADMY
(lead contractor), ICTP, MPI,
the Met Office
PROMISE aims to investigate the influence of SST anomalies
on the variability of monsoon climates, in particular the role of ENSO.
The object of this analysis is to raise awareness of the processes which
must be well simulated by models before climate change predictions for
the tropics can be judged useful.
Key achievements to date:
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the evolution of the Indian Ocena dipole mode has been studied
using EOFs and regression analysis. Whilst the dominant pattern
depicts the basin-wide warming associated with El Nino, the second
mode captures the east-west structure described by the Indian Ocean
dipole. However the variance explained by this pattern is very high
in the east but negligible in the west suggesting the term 'dipole'
is misleading
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analysis of observational data shows that Indian Ocean zonal SST
gradient is a primary control on East African rainfall. It was further
found that this perturbed gradient was, in some years associated
with ENSO
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A series of idealised experiments with an atmospheric GCM have
been designed to investigate the extent to which ENSO teleconnections
contribute to the memory and hence the predictability of the global
circulation. Preliminary results have shown that during the peak
months the global anomalies are primarily driven by the anomalies
in the tropical Pacific. However, several months later, the remote,
lagged response by the global oceans substantially affects the response
in the model particularly over the western Indian Ocean and Africa
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An analysis of the variability and predictability of the Asian
summer monsoon, as represented by numerical simulations with observed
SST (performed in the context of the PRISM project) was carried
out. A detailed statistical analysis of the results indicate the
need for more complex non-linear paradignms for the interpretation
of monsoon variability than those proposed so far in the literature
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the sensitivity of West African rainfall to sea surface temperature
anomalies was studied using an atmospheric GCM forced by perscribed
SST's . It was found that there is a positive correlation between
tropical Atlantic SST anomalies and rainfall on the Guinea Coast
but no correlation between tropical Atlantic SST anomalies and Sahelian
precipitation
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the sensitivity of Sahelian precipitation to Mediterranean SST
anomalies was studied using an atmospheric GCM forced by perscribed
SST in the Mediterranean. It was found that the Mediterranean SST
anomlaies do indeed contribute to the forcing of climatic variability
over the Sahel. The model results were used to infer a dynamic scenario
to explain the mechanism behind this correlation.
Publications on this topic arising from PROMISE
Baquero-Bernal, A., M. Latif, and S. Legutke 2001 On Dipolelike Variability
of Sea Surface Temperature in the Indian Ocean Journal of Climate 15
1358-1368
Black, E., Slingo, J., Sperber, K.R. 2003 An Observational Study of
the Relationship between Excessively Strong Short Rains in Coastal East
Afrcia and Indian Ocean SST Monthly Weather Review 131 74 - 91
Gissila, T., Black, E., Grimes, D. and Slingo, J. 2003 A new seasonal
forecasting system for the Ethiopian Summer Rains International Journal
of Climatology Submitted
Janicot, S., S. Trzaska and I. Poccard 2001 Summer Sahel-ENSO teleconnection
and decadal time scale SST variations Climate Dynamics 18 303-320
Molteni, F., S. Corti, L. Ferranti and J. M. Slingo 2003 Predictability
experiments for the Asian Summer Monsoon: Impact of SST anomalies on
interannual and intraseasonal variability Journal of Climate in press
Quadrelli R, Pavan V, Molteni F 2001 Wintertime variability of Mediterranean
precipitation and its links with large-scale circulation anomalies Climate
Dynamics 17 457-466
Rowell, D.P. 2003 The Impact of Mediterranean SSTs on the Sahelian Rainfall
Season Journal of Climate 16 849-862
Slingo, J. M. and Annamalai, H, 2000 1997: The El Nino of the century
and the response of the Indian Summer Monsoon Monthly Weather Review
128 1778-1797
Spencer, H., Slingo, J.M. and Davey, M. 2003 The influence of the response
by the remote ocean basins on the seasonal predictability of ENSO teleconnections
Climate Dynamics Submitted
Spencer, H. and Slingo, J.M. 2003 The simulation of peak and delayed
ENSO teleconnections Journal of Climate in press
Publications on this topic by PROMISE partners
Slingo, J. M. and H. Annamalai,
2000: 1997: The El Niņo of the century and the response of the Indian
Summer Monsoon. Mon. Weath. Rev., 128, 1778-1797
Soman, M.K. and J. M. Slingo,
1997: Sensitivity of the Asian Summer Monsoon to aspects of the sea
surface temperature anomalies in the tropical Pacific Ocean. Q. J.
R. Meteorol. Soc., 123, 309-336.
Ju, J. and J. M. Slingo,
1995 : The Asian Summer Monsoon and ENSO. Q. J. R. Meteorol. Soc.,
121, 1133-1168.
Rowell, D.P., 2000: Teleconnections
between the tropical Pacific and the Sahel. Q. J. R. Meteorol. Soc.,
Q.J.R. Meteorl. Soc., submitted
Rowell, D.P., Folland, C.K.,
Maskell, K., Owen, J.A. and Ward, M.N., 1992: Modelling the influence
of global sea surface temperatures on the variability and predictability
of seasonal Sahel rainfall. Geophys. Res. Lett., 19, 905-908
Janicot, S. The West African
monsoon of 1987 and 1988 : Pacific or Atlantic signal ? International
Conference on Monsoon Variability and Prediction, Trieste, Italie, WCRP-84,
WMO/TD-No 619, 765-772.
Fontaine, B. and Janicot,
S. Near-global sea surface temperature variability associated with West
African rainfall anomaly types. Journal of Climate, 9,
2935-2940.
Janicot S. Fontaine, B and
Moron, V. ENSO dynamics and Sahel droughts Geophysical Research Letters,
Vol.23, 5, 515-518.
Janicot S. ENSO Impact on
atmospheric circulation and convection over the tropical Atlantic and
West Africa. Annales Geophysicae, 15, 471-475.
Janicot S., Harzallah, A.
Fontaine, B and Moron, V. West African monsoon dynamics and eastern
equatorial Atlantic and Pacific SST anomalies (1970-1988). Journal
of Climate, 11, 1874-1882
Fontaine, B., Trzaska, S
and Janicot, S. Evolution of the relationship between near global and
Atlantic SST modes and the rainy season in West Africa: statistical
analyses and sensitivity experiments. Climate Dynamics, 14,
353-368
Further information
see:
Work package description in the proposal
First annual
report (available to PROMISE partners or with the permission of
the lead contractor)
Second annual report (available
to PROMISE partners or with the permission of the lead contractor)
Third annual report
(available to PROMISE partners or with the permission of the lead contractor)
Final report
or:
contact the lead contractor Julia Slingo (J.M.Slingo@reading.ac.uk)
contact Emily Black (emily@met.reading.ac.uk)
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