Dynamics and Moist Thermodynamics of the Boreal Summer Intraseasonal Oscillation

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Intraseasonal oscillations in the tropics drive week-to-week and month-to-month variations in precipitation and in the risk of tropical cyclones. Thus they are important for the most significant weather and climate variations in these regions. Intraseasonal oscillations in the boreal summer are potentially more complex than the more familiar wintertime Madden-Julian oscillation, because they are not confined to the equatorial band, they exhibit complex interactions with the ocean and with the seasonal mean climate, and they involve a wide range of modes and scales. Current coupled climate models do not simulate the summertime intraseasonal oscillations well.The PIs will analyze observations in order to define the detailed structures of the boreal summer intraseasonal oscillations, including their seasonal variations, the coupling between timescales, and their interactions with seasonal variability. These studies will employ newly available remotely sensed data from satellites, ground-based data, and a very long historical record of precipitation. Modeling studies, using a hierarchy of coupled atmosphere-ocean models, as well as mechanistic intermediate models, will be carried out to identify the mechanisms that drive the BSISO and determine its timescales, to investigate the predictability of the BSISO and its interactions with the ocean, and to explore how it is influenced by seasonal anomalies, such as El Nino.Broader impacts of this work are in the importance of the BSISO for intraseasonal forecasting in the tropics, with implications for predicting floods and droughts, and in training a postdoctoral associate and a graduate student.