An orography-associated extreme rainfall event during TiMREX: Initiation, storm evolution, and maintenance

Weixin Xu Dr., Edward E. Zipser, Yi Leng Chen, Chuntao Liu, Yu Chieng Liou, Wen Chau Lee, Ben Jong Dao Jou

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115 Scopus citations


This study investigates a long-duration mesoscale system with extremely heavy rainfall over southwest Taiwan during the Terrain-influenced Monsoon Rainfall Experiment (TiMREX). This mesoscale convective system develops offshore and stays quasi-stationary over the upstream ocean and southwest coast of Taiwan. New convection keeps developing upstreamoffshore but decays or dies after moving into the island, dropping the heaviest rain over the upstream ocean and coastal regions. Warm, moist, unstable conditions and a lowlevel jet (LLJ) are found only over the upstream ocean, while the island of Taiwan is under the control of a weak cold pool. The LLJ is lifted upward at the boundary between the cold pool and LLJ. Most convective clusters supporting the long-lived rainy mesoscale system are initiated and develop along that boundary. The initiation and maintenance is thought to be a "back-building-quasi-stationary" process. The cold pool forms from previous persistent precipitation with a temperature depression of 2°-4°C in the lowest 500 m, while the high terrain in Taiwan is thought to trap the cold pool from spreading or moving. As a result, the orography of Taiwan is "extended" to the upstream ocean and plays an indirecteffect on the long-duration mesoscale system.

Original languageEnglish
Pages (from-to)2555-2574
Number of pages20
JournalMonthly Weather Review
Issue number8
StatePublished - Aug 2012


  • Mesoscale systems
  • Precipitation
  • Topographic effects


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