The Genesis of Tropical Cyclone Bilis (2000) Associated with Cross-equatorial Surges |
| |
| Authors: | XU Yamei |
| |
| Institution: | Department of Geosciences, Zhejiang University, Hangzhou 310027 |
| |
| Abstract: | The purpose of this paper is to explore how a tropical cyclone forms from a
pre-existing large-scale depression which has been observed and associated
with cross-equatorial surges in the western North Pacific. Tropical cyclone
Bilis (2000) was selected as the case to study. The research data used are
from the results of the non-hydrostatic mesoscale model (MM5), which has
successfully simulated the transformation of a pre-existing weak large-scale
tropical depression into a strong tropical storm. The scale separation
technique is used to separate the synoptic-scale and sub-synoptic-scale
fields from the model output fields.
The scale-separated fields show that the pre-existing synoptic-scale
tropical depression and the sub-synoptic scale tropical cyclone formed later
were different scale systems from beginning to end. It is also shown that
the pre-existing synoptic-scale tropical depression did not contract to
become the tropical cyclone. A series of weak, sub-synoptic-scale low and
high pressure systems appeared and disappeared in the synoptic-scale
depression, with one of the low systems near the center of the
synoptic-scale depression having deepened to become the tropical cyclone.
The roles of the synoptic-scale flow and the sub-synoptic scale disturbances
in the formation of the tropical cyclone are investigated by diagnoses of
the scale-separated vertical vorticity equation. The results show that the
early development of the sub-synoptic scale vortex was fundamentally
dependent on the strengthening synoptic-scale environmental depression. The
depression was strengthened by cross-equatorial surges, which increased the
convergence of the synoptic-scale depression at low levels and triggered the
formation of the tropical cyclone. |
| |
| Keywords: | tropical cyclone genesis cross-equatorial surges scale-separated vertical vorticity equation |
| 本文献已被 CNKI SpringerLink 等数据库收录！ |
| 点击此处可从《大气科学进展》浏览原始摘要信息 |
| 点击此处可从《大气科学进展》下载免费的PDF全文 |
|
