Numerical Study of the Mesoscale Systems in the Spiral Rainband of 0509 Typhoon Matsa |
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Authors: | ZHOU Lingli ZHAI Guoqing and HE Bin |
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Institution: | Department of Earth Sciences, Zhejiang University, Hangzhou 310027, Zhejiang Province Meteorological Observatory, Hangzhou 310017,Department of Earth Sciences, Zhejiang University, Hangzhou 310027,Jiaxing Meteorological Observatory, Jiaxing 314001 |
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Abstract: | The Advanced Weather Research and Forecasting Model (ARW) is used to simulate the local heavy rainstorm process caused by
Typhoon Matsa over the northeastern coast of Zhejiang Province in 2005. The results show that the rainstorm was caused mainly
by the secondary spiral rainband of the Stationary Band Complex (SBC) structure. Within the secondary spiral rainband there
was a strong meso-β-scale convergence line generated in the boundary layer, corresponding very well to the Doppler radar echo band. The convergence
line comprised several smaller convergence centers, and all of these convergence columns inclined outward. Along the convergence
line there was precipitation greater than 20 mm occurring during the following one hour. During the heavy rainstorm process,
the Doppler radar echo band, convergence line, and the precipitation amount during the following one hour, moved and evolved
synchronously. Further study reveals that the vertical shear of radial wind and the low-level jet of tangential wind contributed
to the genesis and development of the convergence columns. The combined effect of the ascending leg of the clockwise secondary
circulation of radial wind and the favorable environment of the entrance region of the low-level jet of tangential wind further
strengthened the convergence. The warm, moist inflow in the lower levels was brought in by the inflows of the clockwise secondary
circulation and uplifted intensely at the effect of convergence. In the convectively instable environment, strong convection
was triggered to produce the heavy rainstorm. |
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Keywords: | typhoon rainstorm convergence line spiral rainband radial wind tangential wind |
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