Typhoons In Taiwan Research Articles

A Comparison of Gauge and Radar‐Derived Rainfall in a Land Falling Typhoon in Taiwan1

Abstract: Precipitation data is generally collected from rain gauge stations. However, each measurement represents only the amount of rainfall at that particular spot, not precipitation in the surrounding area. Radar approaches are considered to offer a good spatial description of precipitation, but hardly predict precipitation quantities with acceptable accuracy. To enhance our understanding of the properties of precipitation in this study, high resolution radar‐rainfall estimates are compared with ground observations for an extreme precipitation event. The Taipei City area and the Shihmen reservoir watershed, situated in northern Taiwan, were chosen as the study sites, and the passage of Typhoon Nari through these areas on September 16‐18, 2001, was taken as the case study event. It was concluded that radar reflectivity from the Wufenshan radar station can be helpful for identifying precipitation variations during the passage of a land falling tropical cyclone. Spots with extreme rainfall can be identified when radar approaches are performed, but not based on gauge approaches, although compared to the gauge approaches to the radar‐estimated rainfall over the investigated domain tended to be overestimated. The divergence between radar‐rainfall and gauge‐rainfall can be identified via subwatershed investigations.

Estimation of waste generation from floods

A framework of correlation for estimating the amount of waste generation from floods is developed. Flood waste data were collected from four recent typhoons in Taiwan. Parameters affecting the flood waste are analyzed. Population density, flooded area and amount of total rainfall are chosen as the correlating parameters for the model development, and regression diagnostics are performed to check the validity of the collected data. The simple linear model is shown to be incapable of correlating the flood waste data. An exponential model is proposed and shown to give acceptable correlation with the flood waste data spanning five orders of magnitude. The model can be useful in the planning of waste cleanup after floods.

Non-contact flood discharge measurements using an X-band pulse radar (II) Improvements and applications

This paper presents and applies an improved method of determining cross-sectional depth and discharge of a river. The method used with the universal law and Darcy-Weisbach friction factors to obtain the lateral variation of the roughness height. This method of measurement was successfully used at the Kaoping River during the Xangsane typhoon in Taiwan, and the results show that the surface velocity obtained using an X-band pulse radar system were close to that obtained by the float method. The estimated discharges at four stages were within 3% of the recorded values of the stage-discharge rating curve in the gauging station.

Debris flow Hazard caused by the 1996 Herb Typhoon in Taiwan

Debris flow Hazard caused by the 1996 Herb Typhoon in Taiwan

An Exploratory Study of the Relationship Between Annual Frequency of Invaded Typhoons in Taiwan and EI Nino/Southern Oscillation

In this study, a nonlinear association between the characteristics of invaded typhoons (hereafter, referred to as ITYs) in Taiwan and sea surface temperature anomalies (SSTAs) over the equatorial eastern Pacific is identified. The relation is such that the years with a warmer-than-normal SSTA condition in the late season generally correspond to fewer annual ITYs (＜4),while those with a cooler SSTA are basically associated with more ITYs (≥4).When the SSTA becomes too cold(≤-1.0℃), however, the annual total number of ITYs is, in fact, greatly reduced (~1-2) instead of being increased. It is suggested that such a phenomenon is caused by different large-scale atmospheric responses to the underlying sea surface temperature conditions. A lower-level anti-cyclonic circulation with strong divergence suppresses the usual activities of tropical cyclones over the western North Pacific (WNP) in the cold years. An opposite mechanism occurs in the early season of the cool years. During the warm years, the typhoon activities over the WNP are not necessarily suppressed but are rather displaced eastward in response to an anomalous cyclonic circulation over the eastern part of WNP. Under such a configuration, however, Taiwan is not in the path of the preferential storm track. This observation appears to be useful in the long term forecasting of typhoon activities in the Taiwan area, as long as the SSTAs can be predicted.