The IRI seasonal climate prediction system and the 1997/98 El Nino event

The International Research Institute for Climate Prediction (IRI) was forme d in late 1996 with the aim of fostering the improvement, production, and u se of global forecasts of seasonal to interannual climate variability for t he explicit benefit of society. The development of the 1997/98 El Nino prov ided an ideal impetus to the IRI Experimental Forecast Division (TRI EFD) t o generate seasonal climate forecasts on an operational basis. In the produ ction of these forecasts an extensive suite of forecasting tools has been d eveloped, and these are described in this paper. An argument is made for th e need for a multimodel ensemble approach and for extensive validation of e ach model's ability to simulate interannual climate variability accurately. The need for global sea surface temperature forecasts is demonstrated. For ecasts of precipitation and air temperature are presented in the form of "n et assessments," following the format adopted by the regional consensus for ums. During the 1997/98 Fl Nino, the skill of the net assessments was great er than chance, except over Europe, and in most cases was an improvement ov er a forecast of persistence of the latest month's climate anomaly.