Study of an Asymmetric and Anticyclonic Bow Echo Near Taiwan

Chung Chieh Wang, Jou Ping Hou*, Chun Hsiang Tseng, Pao Liang Chang, Dong In Lee

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

On 2 April 2007, a strong bow echo struck southern Taiwan, with a peak surface wind speed of 26 m s−1 . On observation, the rear inflow jet (RIJ) was located at the northern flank and only one anticyclonic vortex dominated behind the bow structure. This case was different from commonly occurring cyclonic–anticyclonic pairs of bookend vortices, and was investigated through data analysis, model simulation, and vorticity budget diagnostics. The present bow echo formed at the leading edge of a cold front, with favorable ingredients of instability, large west-southwesterly vertical wind shear, and dry air aloft. Farther behind the front, however, stable conditions could not support deep convection and the portion north of the RIJ was therefore missing. Within a frontal flow structure, the developing mechanism of the anticyclonic vortex also differed from typical cases. As the low-level (west-southwesterly) vertical shear pointed from right to left of the line, and the tilting effect of updrafts generated positive (negative) vorticity at the front (rear) side. South of and below the RIJ, the anticyclonic vorticity was enhanced by the stretching and tilting effect of system-generated horizontal vorticity via a sinking motion. These sources of vorticity were then advected downward and southwestward by the postfrontal flow near the surface.

Original languageEnglish
Article number331
JournalAtmosphere
Volume13
Issue number2
DOIs
Publication statusPublished - 2022 Feb

Keywords

  • Bookend vortex
  • Bow echo
  • Cloud-resolving model
  • Rear inflow jet
  • Taiwan
  • Vorticity budget

ASJC Scopus subject areas

  • Environmental Science (miscellaneous)

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