The impacts of Taiwan topography on the predictability of Typhoon Morakot's record-breaking rainfall: A high-resolution ensemble simulation

Ensemble prediction with realistic topography reproduces salient features of orographic precipitation. The 24-h and 96-h accumulated rainfall amount and distribution from the ensemble mean compares reasonably well with the observed precipitation.

When the terrain of Taiwan is removed, the rainfall distribution is markedly changed suggesting the importance of the orography in determining the rainfall structure. Moreover, the peak 96-h rainfall amount is reduced to less than 20%, and the total rainfall amount over southern Taiwan is reduced to less than 60% of the experiments with Taiwan topography. Further analysis indicates that Taiwan's topography substantially increases the variability of rainfall prediction.