Statistical Characteristics of Typhoon-Induced Rainfall in Taiwan

Typhoon rainfall is an important but challenging forecasting and scientific issue, in particular for Taiwan with high and complicated topography. This study utilizes 21-year (1993-2013) data of all the available automatic rain gauges (about 300 to 500) and conventional rain stations (21) from the Central Weather Bureau (CWB) of Taiwan to investigate the statistical characteristics of typhoon-induced rainfall over Taiwan.

Although the average rainfall amount assessed by the 21 conventional stations is statistically similar to that evaluated by t data from automatic rain gauges, the rainfall data of the 21 conventional stations cannot well capture the main features of the precipitation extremes, nor the rainfall distribution, especially in mountainous areas. The uneven distribution of the 21 conventional stations, only 3 located in mountain areas, is likely to cause such biases of rainfall patterns at higher altitude where major extreme typhoon rainfall occurs. It is thus argued that results evaluated solely based on the 21 conventional data, an approached adopted in a number of previous studies, cannot demonstrate representative statistical characteristics for typhoon-induced rainfall over Taiwan. This study highlights the value of the rainfall measurement over mountain areas in Taiwan, where residents are vulnerable to the risk of destructive rainfall.