Sesasonal predictability of monsoon climates - WP1100

Partners involved: DMI (lead contractor), ECMWF, UREADMY

PROMISE aims to assess the seasonal predictability for monsoon climates using ensembles of model integrations, and with the application of advanced statistical techniques. In addition, the origins of internally and externally forced predictability will be studied.

Key achievements to date:

• evaluation of the ECMWF seasonal forecast system has shown that the pattern of the monsoon circulation at low level is well represented with the Somali jet having the correct location and strength. However, the system dramatically underestimates the strength of upper level easterly flow, even when forced with observed SSTs. Despite this the rainfall distribution over the Indian region is realistic

• investigation of rainfall anomalies averaged over India and over a region covering Burma and Bangladesh shows that the predictability is fairly low

• preliminary assessment of the reproducibility/predictability of the Asian Summer Monsoon rainfall in HadAM3 has been made using an ensemble of AMIP II integrations and multi-decadal integrations with an idealized El Nino/ La Nina cycle. It was found that reproducibility is quite high but that the model systematically predicts rainfall anomalies of the wrong sign over India

• Comparison of the intraseasonal variability simulated by HadAM3 with observation data has shown that the model has difficulty capturing the basic characteristics of monsoon active/break cycles. A detailed study of a number of models suggests that these deficiencies in the simulation of subseasonal modes contribute directly to poor seasonal predictability and to systematic error of the mean state

• All hindcasts in the period November 1986 - May 1992 have been completed. Preliminary indications are that dynamical indices of the circulation over the northern Indian Ocean and southern Asia have some hindcast skill. Examination of a larger time sample will determine statistical significance.

Publications on this topic by PROMISE partners

Ward, M.N., Folland, C.K., Maskell, K., Colman, A., Rowell, D.P. and Lane, K., 1993: Experimental seasonal forecasting of tropical rainfall at the U.K. Meteorological Office. In: Prediction of Interannual Climate Variations, Shukla, J. (Ed.), NATO ASI Series, Vol. I6, Springer-Verlag, Berlin, 197-216

Martin, G.M. (2001) K. Arpe, F. Chauvin, L. Ferranti, K. Maynard, J. Polcher, D.B. Stephenson, P. Tschuck (2001) Simulation of the Asian Summer Monsoon in Five European General Circulation Models. Atmospheric Science Letters DOI:10.1006/asle.2000.0004

Martin, G.M. 1999. The simulation of the Asian Summer Monsoon, and its sensitivity to horizontal resolution, in the UK Meteorological Office Unified Model. Q. J. R. Meteorol. Soc., 125 1499-1525

Martin, G.M. and Soman, M.K. 2000. Effects of changing physical parametrisations on the simulation of the Asian summer monsoon in the UK Meteorological Office Unified Model. Hadley Centre Technical Note No. 17 Available from The Met. Office, London Road, Bracknell, RG12 2SY, U.K.

Stephenson D.B., Kumar K., Doblas-Reyes F-J, Royer J.-F., Chauvin F. and Pezzulli S. (1998) Extreme Daily Rainfall Events and their Impact on Ensemble Forecasts of the Indian Monsoon.Monthly Weather Review 127, 1954-1966

Stephenson, D.B., Chauvin F. and Royer J.-F. (1998) Simulation of the Asian Summer Monsoon and its Dependence on Model Horizontal Resolution Journal of the Meteorological Society of Japan 76, 237-265

Sperber, K. R., J. M. Slingo and H. Annamalai: Predictability and the relationship between subseasonal and interannual variability during the Asian Summer Monsoon. Q. J. R. Meteorol. Soc., in press.

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 Wilhelm May (may@dmi.dk)
contact Emily Black (emily@met.reading.ac.uk)