Impact of Surface Drag of Islands in the Maritime Continent on the Atmospheric General Circulation

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Abstract
In most general circulation models, the "maritime continent" is poorly resolved because there are many islands too small to be represented in the model. We investigate a possible effect of these small islands on the atmospheric general circulation by introducing surface drag over islands in model's ocean grid points.It is shown that the increased drag coefficient in the maritime continent is very effective in increasing the precipitation there by inducing stronger moisture flux convergence. Walker-type circulation anomaly is distinct over the entire equatorial Pacific along with the westerly anomaly in the lower troposphere over the Indian Ocean. There are also large impacts on both the Asian and the Australian monsoon not only for their strength but also for the onset/duration. These results imply the need of carefully handling surface conditions around the maritime continent where moisture flux convergence/heating feedback is strong, by considering the surface heterogeneity.