9712483 Waliser This grant represents one of the two awards that provide support for a collaborative project between Dr. Duane Waliser at SUNY - Stony Brook and Dr. Charles Jones of UC - Santa Barbara (under ATM-9712855). The principal investigators seek to improve our understanding of, and ultimately our capability to forecast, a tropical intraseasonal phenomenon known as the Madden-Julian Oscillation (MJO). The Madden-Julian Oscillation is one of the most important modes of tropical intraseasonal variability that may have important influences on medium- to extended-range weather forecasting in the extratropics, the Asian-Australian monsoon activity, and even the variability of the equatorial Pacific Ocean thermocline structure via its close association with westerly wind bursts. A growing body of evidence, including recent modeling results obtained by the principal investigators, suggests that air-sea interaction processes, particularly the influence of sea-surface temperature (SST) variations on surface fluxes, may be important in the maintenance of the MJO. The principal investigators will continue their investigation by (1) further exploring the role of SST and surface processes in determining the strength of and maintaining the MJO using coupled ocean-atmosphere models and (2) assessing the impact of the representation/forecast of the MJO on the overall extended range forecast skill in an operational medium-range weather forecast model. The research will involve the use of diagnostic and statistical analyses as well as numerical simulations. The PIs will employ several different models in their study. This research has important implications for improving dynamical extended range forecasting at both intraseasonal and seasonal time scales. Therefore, both the Climate Dynamics and Large-scale Meteorology Programs will share in the support of this collaborative project.