遲正祥1 周昆炫 2 -...
TRANSCRIPT
-
辛樂克颱風(2008)侵台期間眼牆演變研究 A study of Eyewall Evolution of Typhoon
Sinlaku (2008) Crossing the Taiwan terrain
遲正祥1 周昆炫2
-
Introduction
• In
the
past,
a
number
of
papers
have
studied the
landfall
evolution
of
TCs
(Brand
and
Blelloch 1973, 1974; Yeh
and Elsberry 1993a,b; Wu
and
Kuo
1999;
Wu
2001;
Wu
et
al.
2002;
Chen and Yau 2003).
-
Introduction
• Huang
et
al.
(2010)
indicate
that
the
terrain height
of
Taiwan
plays
the
most
important
role
in
Typhoon
Krosa’s
looping
motion
at
its landfall.
-
Introduction
• Wu
et
al.
(2003;
2009)
indicated
that
the eyewall
may
contract
and
breakdown
at
before
and
after
when
typhoon
Zeb
(1998) crossing Philippines.
-
Introduction
Zeb(1998) was demonstrated by Wu et al. (2009)
-
Introduction
• Wu
et
al.
(2009)
investigated
that
sensitivity experiments
about
different
terrain
hight
and
demonstrated
these
results
were
system qualitative pheonomena.
Full terrain Flat Sea
-
Introduction
• An observational study about typhoon approaching different terrain (Taiwan and
Philippines) also documented in Chou et al. (2011).
-
Introduction
By Chou et al. (2011)
-
Introduction
• But,
the
previous
studies
had
never
note
the numerical
simulation
results
in
Taiwan
about
this phenomena mentioned above.• In
fact,
there
were
few
papers
refer
to
the
effect
of
typhoon
size
cause
that
was
a difficult operation to define a accurate size by a
objective
law.
In
the
strict
sense,
the
size
condition
would
be
sure
to
conduct
a
certain effect. (Merrill et al. 1984)
-
Motivation
• This
study
will
investigate
the
eyewall
evolution of Typhoon Sinlaku
(2008) at a landfall period by
WRF
model
to
describe
the
numerical experiment results consist with the observation.
• In
addition,
the
interaction
between
typhoon eyewall
(size and strength) and terrain would
be
discussed in this study.
-
Motivation
• This case was also included in Chou et al. (2011) and T‐PARC experiments.
-
Model description
-
Model description
• Bogus scheme refer to Wu et al. (2001)• Using Rankine
vortex before integration 6 h
• Domain:
-
Part I : Experiment design
• Integration time: 5 days periods2008/9/11 0000 UTC –
2008/9/16 0000UTC
-
Model results
-
Model results
• The axisymmetric
average tangential wind of hovemoller diagram.
m/s
NB(CTL) BM FLAT NT
-
Model results
• The axisymmetric
average rainfall of hovemoller
diagram.
NB(CTL) BM FLAT NT
mm
-
Part II: Experiment design
• Integration time: 5 days periods• 2008/9/11 0000 UTC –
2008/9/16 0000UTC
• size sensitivity design from 1100 model cases.
Experiments Description (Bogus size of
radius (km))Vmax
(m/s)Rmax
(km)α
BSS 150 55 35 0.5
BMS 150 55 40 0.5
BLS 200 55 35 0.5
BVLS 200 55 40 0.5
-
Part II: Experiment design• PartII‐Rmax sensitivity • PartII‐Size sensitivity
-
Model results(Part II‐Rmax sensitivity)
-
Model results(Part II‐Rmax sensitivity)
m/s
• The axisymmetric average tangential wind of hovemoller diagram.
-
Model results(Part II‐Rmax sensitivity)
The
interaction
between
Taiwan
terrain and
eyewall
Rmax
sensitivity
experiments
show
that
the
larger
inner eyewall
would
induce
outer
eyewall
contract
and
rainfall
more
easily
when votex approaching Taiwan.
-
Model results(Part II‐Rmax sensitivity)
To
investigate
this
phenomena,
choose 16
similar
cases
and
calculate
average.
The result consist with above discussion.
-
Model results(Part II‐Strength sensitivity)
The
outer
field
(radius 1~2
degree)
of
large
strength
is
stronger than
small
strength,
which
is
same
for
Rmax sensitivity experiments.
-
Summary
• The
eyewall
contract
before
landfall
and breakdown
after
landfall
was
simulated
by
WRF
model
in
Sinlaku
case;
Taiwan
terrain certainly
play
a
critical
role
by
sensitivity
experiments.• After
breakdown,
the
outer
wind
field
would
contract
again
and
rebulid
a
new
bigger eyewall.
-
Summary
• The
size
sensitivity
experiments
indicate
that the concentration of larger vortex will induce stronger
outer
wind
and
rainfall
easily
and
vice versa.
-
Future work
• To
filter
environmental
influence,
investigate the terrain and vortex size by ideal model.
• Consider
the
angular
momentum
budget analysis
from
the
ideal
case
to
obtain
a
quantitative results.
-
END
辛樂克颱風(2008)侵台期間眼牆演變研究�A study of Eyewall Evolution of Typhoon Sinlaku (2008) Crossing the Taiwan terrainIntroductionIntroductionIntroductionIntroductionIntroductionIntroductionIntroductionIntroductionMotivationMotivationModel descriptionModel descriptionPart I : Experiment designModel resultsModel resultsModel resultsPart II: Experiment designPart II: Experiment designModel results(Part II-Rmax sensitivity)Model results(Part II-Rmax sensitivity)Model results(Part II-Rmax sensitivity)Model results(Part II-Rmax sensitivity)Model results(Part II-Strength sensitivity)SummarySummaryFuture workEND