Abstract
In this study, structural features of a subtropical prefrontal rainband associated with the Mei-Yu front on 25 June 1987 over northwestern Taiwan are investigated. Dual-Doppler data collected during the Taiwan Area Mesoscale Experiment (TAMEX) were employed to derive fields of reflectivity, system-relative wind and vertical velocity in a horizontal domain of 36 by 40 km using a 1 km grid spacing. There were ten analysis levels in the vertical ranging from 0.4 to 8.8 km. Vertical velocities were calculated from the anelastic continuity equation by integrating downward with variational adjustment.
Results show that the low-level jet (LLJ) in the boundary layer provides large vertical shear ahead of the front. The southwest monsoon flow at low-levels carries high-θ e environmental air northeastward meeting with the northwesterly flow from northern China to form distinct wind-shift line. This windshift line corresponds well to the position of the Mei-Yu front. Along the wind-shift line, the low-level convergence enhances lifting resulting in a narrow band of convection on the warm side of the front. There are many cells embedded within the rainband. Each cell is accompanied by the moderate convective updraft and weak downdraft. The precipitation is deep but not intense ahead of the front, while the precipitation behind the front is weak and shallow. Because the system traveled very slowly, up to 200 mm of rainfall in 24 hours occurred on the west coast of central Taiwan causing a flash flood over that region.
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Lin, YJ., Pasken, R.W. & Chang, HW. Structure of a prefrontal convective rainband in northern Taiwan determined from Dual-Doppler data. Nat Hazards 9, 37–61 (1994). https://doi.org/10.1007/BF00662590
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DOI: https://doi.org/10.1007/BF00662590