Dynamics of the Tropical Intraseasonal Oscillation

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Abstract ATM-9400759 Wang, Bin University of Hawaii Title: Dynamics of the Tropical Intraseasonal Oscillation The goal of this proposed research is to futher develop physical understanding of the complex behavior of tropical intraseasonal disturbances (TIS). The results gained from the study are expected to be useful for future predictions of MJO and related climate variations. Three interrelated research projects will be undertaken. 1. Interaction of TIDS and mean tropical circulations A three-layer tropical atmospheric model describing both the moist equatorial waves and time-mean flows will be used to investigate the effects of a three-dimensional mean flow on wave development and propagation, and the change of mean flow caused by momentum and heat transports (or E-P flux) associated with wave activities. 2. Interaction of MJO and tropical ocean To understand the nature of atmosphere-ocean interaction on intraseasonal time scales, the PI will (a) perform numerical experiments with an intermediate tropical ocean model to access the possible influences of an ensemble of intraseasonal forcing on the ENSO cycle, (b) conduct an empirical study of the relation between intraseasonal variation of SST and MJO to access the degree of the coupling between SST and MJO, and c) analyze coupled instability possibly arising from the thermodynamic coupling of the atmosphere and ocean relevant to warm ocean regions. 3. Multi-scale structure of MJO and higher-frequency disturbances The PI will investigate the multi-scale temporal and spatial structure of the MJO and its relation to cloud clusters, tropical cyclones, and extratropical forcing, using wavelet analysis and other effective means. A strategy of combining theoretical, numerical, and empirical analyses is adopted. Empirical analysis is used for revealing new facts and formulating hypotheses, while theoretical and numerical modeling are used to explain the phenomenon and te st the hypotheses. This research is important because it seeks to understand variability on intraseasonal time scales.