the meso-scale features associated with typhoon mindulle (2004) when it was affecting taiwan
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The Meso-scale Features Associated with Typhoon Mindulle (2004) When It Was Affecting Taiwan Cheng-shang Lee, Yi-chin Liu (NTU), Fang-ching Chien (NTNU). Daily Rainfall (mm). Operational fixes of Mindulle (CWB). July 1. July 2. - PowerPoint PPT PresentationTRANSCRIPT
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The Meso-scale Features
Associated with Typhoon Mindulle (2004)
When It Was Affecting Taiwan
Cheng-shang Lee, Yi-chin Liu (NTU), Fang-ching Chien (NTNU)
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Operational fixes of Mindulle (CWB)
Mindulle and the following southwesterlies brought 1,860 mm rainfall to Taiwan– locally called 7-2 flood.
July 1
July 2
Daily Rainfall (mm)
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Rainfall on July 1 (max ~ 383 mm)-- mainly by the terrain slope lifting of typhoon circulation
Rainfall on July 3 - 4 (max over 700 mm) (Chien et al. 2006)
-- mainly by the southwesterly flow (occurred over CMR)
Rainfall on July 2 (max ~ 787 mm)-- multiple factors (meso-scale features) are playing roles.
Focus of this talk:
Meso-scale processes occurred on July 2 - focus on the evolution of the secondary center
Interaction between secondary center and main center.
The influences of secondary center and typhoon circulation on the heavy rainfall.
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Surface analysis and visible satellite imageries
A secondary low formed over Taiwan Strait -
moved toward the ENE, made landfall and then dissipated.
1500 UTC 1 July 2100 UTC 1 July
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Composite radar reflectivity (CWB)
0702 1700 UTC
0702 0200 UTC
0702 1200 UTC Heavy rainfall ~highly related torainbands,
which occurred to the south of the secondary center.
0702 0600 UTC
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MM5 model setup• Initial data: EC Advanced Data Set
TC bogus at 12 h before initial time (Jien et al., 2003, 2005)
• Simulation time:
0100~0300 UTC July, 2004
• D1: 160×160, 45km
D2: 154×154 ,15km
D3: 133×133 , 5km
• Physics options
Cumulus: Grell
PBL: MRF
IMPHYS: Mixed-Phase
• Objective analysis: little-r
• FDDA
Analysis based on MM5 model simulation
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Tracks of primary and secondary centers -model simulation vs. observation
Secondary center
Primary center
Model simulates reasonably welltracks of primary and secondary centers.
(0206)
(0123)
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701
739
500
Accumulated daily rainfall (July 2, 2004)
Simulation (24~48h)Observation
Model reproduces reasonably well the rainfall distribution.
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12 h 20 h 28 hEvolution of primary (red) and secondary (blue) centers
3 h before landfall 5 h after landfall 13 h after landfall
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32 h 36 h 42 h
2 h after moving off-shore 6 h after 12 h after
Evolution of primary (red) and secondary (blue) centers
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Trajectories during the developing phase of the secondary low (backward trajectory: 18 hr 8 hr)
Two groups of air parcel trajectories
Over CMR
Around CMR
2
21
1
Subsidence warming produced the initial low pressure.
Flow around the northern tip of CMR brought in shear vorticity for the further development of the secondary low.
P and Theta at 1.5 km AGL
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Vorticity averaged inside box A (include matured vortex)
Height
time
Stages of low-level vortex:developing – 12 ~ 20 hmature – 20 ~ 26 h max vorticity ~ 2.5X10-4 s-1
disappearing – 26 ~ 30 h
A
925 hPa vorticity (shaded)P msl and 10 m winds
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The low level ( 950 ~ 800hPa )
Times LC HA VA DT TT RT
12-20 h 4.3 3.5 -0.03 1.0 1.6 -1.820-26 h 0.16 -5.4 9.1 9.9 -7.4 -6.1
26-30 h -6.0 -17.0 5.6 10.5 -3.3 -1.9
The midlevel ( 800 ~ 500 hPa )
Times LC HA VA DT TT RT
12-20 h 2.9 3.6 0.56 -1.6 0.53 -0.1620-26 h 2.1 0.74 1.9 -0.83 0.83 -0.57
26-30 h -1.1 -3.6 3.4 0.90 -1.4 -0.36
TRp
u
y
ω
p
v
x
ωvζf
p
ζωζfv
t
ζ
Vorticity budgetLC HA VA DT TT RT
HA ~ advection of shear vorticity from the north of the CMR
HA ~ vorticity of primary center moved across the CMR
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Before landfall After landfall
LL
Evolution of secondary center – a schematic diagram
L
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For the secondary vortex at mature stage Area-averaged vorticity ~ 2.5X10-4 s-1
Rossby radius of deformation ~ 120 km (if c = 30 m/s). Heating would be efficient for secondary vortex to develop.
Why the secondary vortex didn’t replace the primary center?
1.5 PVU at σ= 0.9 (27- 33 h)
What has happened to the low-level primary center?
The strong vorticity remnant associated with the primary center moved northward on the eastern side of the CMR.
The primary center re-developed after it moved off shore.
An unique feature of a northward- moving typhoon?
(Similar for Ofelia, 1990)
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After primary center re-developed over the ocean ~7/2 0500 UTC 7/2 0700 UTC
7/2 0900 UTC 7/2 1100 UTC
Shaded: PV at σ= 0.9, Contour: 900 hPa gpm
Two centers rotated cyclonically wrt each other
landfall of secondary center
(dissipated over land)
A reasonable result for a typhoon with such track pattern.
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28 h
34 h
28 h
34 h
Sensitivity test (no initial vortex) no typhoon and no secondary vortex
Div at σ= 0.9 (strong conv shaded)
SW flow
Meso-scale circulation Terrain
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Summary
Horizontal vorticity advection is important to the spin-up of the secondary vortex (Lin et al. 2006).
It is difficulty for the secondary center to replace the primary center for a typhoon northward moving (along the east coast of Taiwan).
Several factors are affecting the heavy rainfall on 2 July for Mindulle (2004) case:
typhoon circulation, secondary centersouthwesterly flow, Taiwan topography.
Thank you!