Idealized simulations of Mei-yu rainfall in Taiwan under uniform southwesterly flow using a cloud-resolving model

Chung Chieh Wang, Pi Yu Chuang*, Shi Ting Chen, Dong In Lee, Kazuhisa Tsuboki


研究成果: 雜誌貢獻期刊論文同行評審

2 引文 斯高帕斯(Scopus)


In this study, idealized cloud-resolving simulations are performed for horizontally uniform and steady southwesterly flow at fixed direction-speed combinations to investigate rainfall characteristics and the role of the complex topography in Taiwan during the Mei-yu season without the influence of a front or other disturbances. Eight directions (180 to 285ĝ , every 15ĝ ) and eight speeds (5 to 22.5ĝ€¯ms-1, every 2.5ĝ€¯ms-1) are considered, and near-surface relative humidity is also altered (from 55ĝ€¯%-100ĝ€¯%) in a subset of these tests to further examine the effects of moisture content, yielding a total 109 experiments each having a integration length of 50ĝ€¯h. Three rainfall regimes that correspond to different ranges of the wet Froude number (Frw) are identified from the idealized simulations (with a grid size of 2ĝ€¯km). The low-Frw regime (Frwĝ€¯≤ ĝ1/4ĝ€¯0.3) is where the island circulation from thermodynamic effects is the main driver of rainfall in local afternoon. The lower the wind speed and Frw are, the more widespread the rainfall is, as well as its amount. On the other hand, the high-Frw regime (Frwĝ€¯≥ĝ€¯ĝ1/4ĝ€¯0.4) occurs when the flow of at least 12.5ĝ€¯ms-1 impinges on Taiwan terrain at a large angle (not parallel). This favors the flow-over scenario, and topographic rainfall production becomes dominant through mechanical uplift of unstable air. In this scenario, the faster and wetter the flow is, the heavier the rainfall on the windward slopes is, and maximum amounts typically occur at wind directions from 240-255ĝ . Between the two regimes above, a third, mixed regime also exists. The idealized results are discussed for their applicability to the real atmosphere.

頁(從 - 到)1795-1817
期刊Natural Hazards and Earth System Sciences
出版狀態已發佈 - 2022 6月 2

ASJC Scopus subject areas

  • 一般地球與行星科學


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