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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:

  • 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 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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