THE SECONDARY LOW AND HEAVY RAINFALL ASSOCIATED WITH TYPHOON MINDULLE (2004) Speaker : Deng-Shun...
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Transcript of THE SECONDARY LOW AND HEAVY RAINFALL ASSOCIATED WITH TYPHOON MINDULLE (2004) Speaker : Deng-Shun...
THE SECONDARY LOW AND HEAVY RAINFALL ASSOCIATED WITH TYPHOON MINDULLE (2004)
Speaker : Deng-Shun ChenAdvisor : Prof. Ming-Jen Yang
Lee, C.-S., Y.-C. Liu and F.-C. Chien, 2008:The Secondary Low and Heavy Rainfall Associated with Typhoon Mindulle(2004). Mon. Wea Rev., 136, 1260-1283.
1
The 7-2 Flood Was Caused by MINDULLE
2
College Entrance Examination
3
Outline 4
Case description Model design and verification a) model settings b) verification of the simulation The evolution of the primary and the
secondary centers Budget analyses during the formation of
secondary low a) thermal budget b) vorticity budget The roles of the secondary low Discussion and conclusion
Case description 5
Synoptic Scale 6
500 hPa 7/1 1200Z
500 hPa 7/2 1200Z
Mesoscale Surface Analyses7
1500Z 1 July surface
0000Z 2 July surface
Visible Satellite8
NCU Radar Observation 9
0241Z & 0316Z 2 July
CWB Radar Reflectivity 10
20Z 1July
02Z 2 July
12Z 2 July
17Z 2 July
24-h Accumulation Rainfall (mm)
11
00Z 1 July – 00Z 2 July
00Z 2 July – 00Z 3 July
00Z 3 July – 00Z 4 July
12
Model design and verification
a) model setting b) verification of the simulation
Model MM5
Domain D1:45 km ; D2: 15 km ; D3: 5 km , two-way interaction
Levels 31 levels, extend vertically up to100 hPa
Microphysics Resiner Mixing – Phase ( Reisner et al. 1998)
PBL Medium-Range Forecast (MRF) PBL (Hong et al.)
Radiation Simple Cooling Radiation Scheme
ICECMWF/TOGA 1.125 。 X 1.125 。 resolution
BC
cumulus Grell cumulus parameterization (Grell et al. 1994)
Model Setting 13
Accumulation Rainfall (Sim. vs. Obs.)
15
Simulation
Observation
00Z 2 July – 00Z 3 July
Geopotential Height at 925-hP and Reflectivity
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28 h 34 h
The Evolution of Primary & Secondary Low (I)
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12 h 20 h 28 h
The Evolution of Primary & Secondary Low (I)
18
32 h 36 h 42 h
Geopotential Height & Potential Vorticity
19
TT
T
T TCC C
500 hPa
17h 19h 21h
23h 25h 27hPrimary center merged with secondary low
Horizontal Wind & Potential Temperature
20
6h 12h
At 2 km AGL
SLP & PV (I)21
8 h 12 h
SLP : Sea Level Pressure, PV : Potential Vorticity
SLP & PV (II)22
16 h 20 h
SLP & PV (III)23
30 h 34 h
26
Budget analyses during the formation of secondary low
a) Thermal budget b) Vorticity budget
Thermal Budget 27
8h 18h
1 2 3 4 5
Condensational heating
Thermal Budget Result28
Model 8 h
Vertical advection
Model 8 h
Local change term
Model 18 h
Vertical advection
Model 8 h
Local change term
Potential Temperature & Trajectory
29
The Representation of Trajectory
30
Trajectory 1 The sinking motion resulted in adiabatic
warming also is the early stage formation of the secondary low at low level.
Trajectory 2 The air parcels that transported vorticity
to the low pressure region which assisted the development of the secondary low.
Vorticity Budget 31
Local Change LC
Horizontal Advection
HA
Vertical Advection
VA
Divergence Term
DT
Tilting Term TT
Residual Term RT
Vorticity Budget Result32
DevelopingMatureDisappearing
DevelopingMatureDisappearing
Distribution of LC, HA and DT
33
12-16 h
16-20 h
LC HA DT
The Roles of the Secondary Low (I)
34
The interaction between the primary center and the secondary center
Fujiwhara effect
The reason why secondary low did not replace the original center
The Roles of the Secondary Low (II)
35
Impact of the secondary low and the typhoon circulation on rainfall
III
I
28h 34h
Conclusion (I)36
Two processes resulted in the formation of a secondary low ,1) downslop adiabatic warming ,2) the shear vorticity that circled around the northern tip of the CMR.
The low level horizontal vorticity advection and then local convergence further concentrated the vorticit.
The vortex stretching and advection are dominant terms during the formation of the secondary low(Chang ,1982)
Conclusion (II)37
Mindulle can be treated as a ‘‘quasi-continuous track’’
Such results are somewhat different form the previous studies that show weaker typhoons having more chances to induce a secondary low. (Chang 1982)
The secondary low and the typhoon circulation played an important role in the heavy rainfall over the central and southern parts of the island west of the CMR.
Conclusion (III)38
It is impossible to isolate the role of typhoon circulation and secondary low on the heavy rainfall.
The secondary low should play a role as a modification of environmental flow, which could result in the west-east convergence lines.
Question ?