Collaborative Research: The Effect of Near-Equatorial Islands on Climate

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This project will examine the effect of near-equatorial islands on climate. A series of experiments, first with a simple, two-dimensional model without the effects of rotation, and then with the Massachusetts Institute of Technology General Circulation Model (MIT-GCM) will be carried out to examine the effects of islands on the distribution of rainfall, the resulting wind field, and hence on large-scale circulation. Experiments with the MIT-GCM will be carried out with simplified geometries that include barriers of negligible width to ocean circulation, but not atmospheric, circulation and with different numbers, distributions, lateral dimensions, and elevations of tropical islands in order to seek scaling relationships between these measures of island extent and the response of the atmosphere and ocean. The goals are two-fold: First, could the growth of islands to build the Maritime Continent have altered atmospheric circulation sufficiently to change the sea-surface temperature distribution in the equatorial Pacific from one resembling a permanent El Niño-like state to its present mean weak La Niña-like state? Second, can parameterizations be derived for the effects of islands on tropical precipitation and ascent that allow GCMs to include the effects of islands that are too small to be resolved in such global models? The broader impacts are high: if islands do play a major role in climate, this study will yield parameterizations that will be useful for including the effects of small islands in model simulations. In addition this work will support a graduate student. .