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Chun-Chieh Wu
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Chun-Chieh Wu
and
Ying-Hwa Kuo

Of all the natural disasters occurring in Taiwan, tropical cyclones are the most serious. Over a 20-yr period, Taiwan was hit by an average of 3.7 typhoons per year. These storms can produce heavy rainfall and strong winds, leading to severe damage to agriculture and industry, and serious loss of human life. An outstanding example is Typhoon Herb, which made landfall in Taiwan on 31 July 1996. Typhoon Herb took 70 lives and caused an estimated $5 billion of damage to agriculture and property.

Accurate prediction of the track, intensity, precipitation, and strong winds for typhoons affecting Taiwan is not an easy task. The lack of meteorological data over the vast Pacific Ocean and the strong interaction between typhoon circulation and Taiwan's mesoscale Central Mountain range are two major factors that make the forecasting of typhoons in the vicinity of Taiwan highly challenging. Improved understanding of the dynamics of typhoon circulation and their interaction with the Taiwan terrain is needed for more accurate prediction. With this objective in mind, the National Science Council in Taiwan sponsored the Workshop on Typhoon Research in the Taiwan Area at Boulder, Colorado, on 17–18 May 1997. In this paper, the authors review the observational and numerical studies of typhoons affecting Taiwan, present some preliminary results from the study of Typhoon Herb, summarize the recommendations obtained from the workshop, and provide suggestions for future research.

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Chun-Chieh Wu
,
Tzu-Hsiung Yen
,
Yi-Hsuan Huang
,
Cheng-Ku Yu
, and
Shin-Gan Chen

Abstract

This study utilizes data compiled over 21 years (1993–2013) from the Central Weather Bureau of Taiwan to investigate the statistical characteristics of typhoon-induced rainfall for 53 typhoons that have impacted Taiwan. In this work the data are grouped into two datasets: one includes 21 selected conventional weather stations (referred to as Con-ST), and the other contains all the available rain gauges (250–500 gauges, mostly automatic ones; referred to as All-ST). The primary aim of this study is to understand the potential impacts of the different gauge distributions between All-ST and Con-ST on the statistical characteristics of typhoon-induced rainfall. The analyses indicate that although the average rainfall amount calculated with Con-ST is statistically similar to that with All-ST, the former cannot identify the precipitation extremes and rainfall distribution appropriately, especially in mountainous areas. Because very few conventional stations are located over the mountainous regions, the cumulative frequency obtained solely from Con-ST is not representative. As compared to the results from All-ST, the extreme rainfall assessed from Con-ST is, on average, underestimated by 23%–44% for typhoons approaching different portions of Taiwan. The uneven distribution of Con-ST, with only three stations located in the mountains higher than 1000 m, is likely to cause significant biases in the interpretation of rainfall patterns. This study illustrates the importance of the increase in the number of available stations in assessing the long-term rainfall characteristic of typhoon-associated heavy rainfall in Taiwan.

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Stephen A. Cohn
,
Terry Hock
,
Philippe Cocquerez
,
Junhong Wang
,
Florence Rabier
,
David Parsons
,
Patrick Harr
,
Chun-Chieh Wu
,
Philippe Drobinski
,
Fatima Karbou
,
Stéphanie Vénel
,
André Vargas
,
Nadia Fourrié
,
Nathalie Saint-Ramond
,
Vincent Guidard
,
Alexis Doerenbecher
,
Huang-Hsiung Hsu
,
Po-Hsiung Lin
,
Ming-Dah Chou
,
Jean-Luc Redelsperger
,
Charlie Martin
,
Jack Fox
,
Nick Potts
,
Kathryn Young
, and
Hal Cole

Constellations of driftsonde systems— gondolas floating in the stratosphere and able to release dropsondes upon command— have so far been used in three major field experiments from 2006 through 2010. With them, high-quality, high-resolution, in situ atmospheric profiles were made over extended periods in regions that are otherwise very difficult to observe. The measurements have unique value for verifying and evaluating numerical weather prediction models and global data assimilation systems; they can be a valuable resource to validate data from remote sensing instruments, especially on satellites, but also airborne or ground-based remote sensors. These applications for models and remote sensors result in a powerful combination for improving data assimilation systems. Driftsondes also can support process studies in otherwise difficult locations—for example, to study factors that control the development or decay of a tropical disturbance, or to investigate the lower boundary layer over the interior Antarctic continent. The driftsonde system is now a mature and robust observing system that can be combined with flight-level data to conduct multidisciplinary research at heights well above that reached by current research aircraft. In this article we describe the development and capabilities of the driftsonde system, the exemplary science resulting from its use to date, and some future applications.

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