| Summary: | 博士 === 臺灣大學 === 大氣科學研究所 === 98 === This study demonstrates that during the passage of the MJO through the Maritime Continent in the boreal winter, the corresponding circulation structure, cloud systems, as well as consequential heating profiles, are redistributed via complex topographic effects from mountainous islands. The effects could be summarized as follows. 1) Overall, more spatially-elongated and higher mountainous islands exert stronger blocking effect on the incoming flow. 2) The blocking effect of the elongated and high-rising New Guinea is so strong that it causes a complete flow bifurcation from the surface to above 500-hPa. 3) The long but low island chain of Sumatra and Java not only results in the southward deflection of the incoming westerly anomaly, but also allows the westerly anomaly to flow over and creates vertical wave-like perturbation in the downstream. 4) Less spatially-extended islands such as Sulawesi and Borneo exert only a localized blocking effect, causing significant downstream wave-like perturbation in the vertical. Distinctive vorticity and convergence distributions are therefore generated in this specific domain. The existence of topography seems to create extra lifting and sinking within the large-scale circulation and thus the convective system exhibits quasi-stationary features near the major topography during the MJO passage through the Maritime Continent. Associated precipitation, turbulent and radiative flux anomalies at TOA and surface are therefore affected. It is suggested that resolving the detailed topographic effects may play a key role in simulating realistic characteristics of the MJO in the Maritime Continent, while ignoring influence from tropical topography with an aqua-planet model may not be a proper approach for our further understanding of MJO.
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