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:
-
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
-
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
-
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
-
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
-
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
-
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 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
Detailed
annual report (available to PROMISE partners or with the permission
of the lead contractor)
18 month progress reports submitted by the partners for this work package
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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