Upload
edgardo-slaten
View
215
Download
0
Embed Size (px)
Citation preview
On the Rapid Intensification of Hurricane Wilma (2005)
Hua Chen
Committee members: Dr. Da-Lin Zhang (Advisor) Dr. James Carton
Dr. Chuan Liu (Dean’s Representative) Dr. Xin-Zhong Liang
Dr. Kayo Ide Dr. Takemasa Miyoshi
Overview of Hurricane Wilma (2005)
• Record intensity in the Atlantic basin – 882 hPa
• Record intensification rate: 54 hPa/6 h, 83 hPa/12h, and 97 hPa/24 h (RI Def: > 1.5 hPa/hr)• Record small eye size: 5 kilometer in diameter
• Huge storm surge: 12 - 14 feet surge
• Torrential rainfall: 1600 mm rainfall/24h at Yucatan peninsula
Above the mean fcst errors: track - 160 km/48 h, 250 km/72 h, andlarge intensity underforecast (GFDL: 924 hPa and 50 m s-1).
Outline• Numerical prediciton• Model description• Model Verification
• Diagnostic analysis• The upper level warm core• Small symmetric eyewall
Model Description (WRF-ARW)
• Two-way, movable, quadruply nested (27/9/3/1 km), 55 levels in the vertical;
• Thompson et al. (2004) 3-ice cloud microphysics scheme;• The Betts-Miller-Janjic cumulus scheme for 27 and 9 km;• The YSU PBL scheme;• NOAH surface-layer physics;• Cloud-radiation interaction scheme;• Initial and boundary conditions: The GFDL’s then
operational data, except for the specified daily SST;• Integration period: 0000 UTC 18 ~ 0000 UTC 21 October
2005 (72 h) for all the four meshes.
A
B
C D1
DN
NASA/GSFC, 26 March 2012
The best track (dashed) vs the 72-h predicted track (solid),SST (shaded), SST (00 Z 19 – 00 Z 18; contoured)
Observed
Predicted
0 6 12 18 24 30 36 42 48 54 60 66 72
880
900
920
940
960
980
1000
MA
XIM
UM
SUR
FAC
E W
IND
(M S
-1)
CE
NT
RA
L P
RE
SSU
RE
(hP
a)
MODEL HOUR18/00 19/00 20/00 21/00
10
20
30
40
50
60
70
80
90
VOBS
VPRE
POBS
PPRE
Pre-RI
RI Post-RI
A
BC
D
Visible Satellite picture Predicted reflectivity at 1-km altitude
1900 UTC 18 OCT 1800 UTC 18 OCT
a b
c d
N-S
SE-NW
SW-NE
NE-SW
SE-NW
NW-SE
N-S
SW-NE
W-E
S-N
W-E
W-E
W-E
W-E
W-E
W-E
W-E
W-E
18/2130
19/1800 19/1800
19/2140
20/0512
20/0650
20/1020
20/1845
20/2140
18/1830-18.5
19/1800-42
19/2030-44.5
19/2100-45
19/2300-47
20/0500-53
20/0700-55
20/1030-58.5
20/1800-66
20/2100-69
Radius (km) Radius (km)
Verification against the flight-level observations
RMW = 7 kmRMW = 15 km
Observed Predicted
Hypothesis – upper level warm core
• An upper level warm core is important for RI;• The upper level warm core results from the descending
air in the lower stratosphere due to convective bursts• This upper level warm core is protected by the
symmetric divergent outflow at upper level from ventilation;
• Convective bursts, driven by high SSTs, play an important role in generating the upper-level warm core.
Hypothesis – upper level warm core
• An upper level warm core is important for RI;• The upper level warm core results from the descending
air in the lower stratosphere due to convective bursts• This upper level warm core is protected by the
symmetric divergent outflow at upper level from ventilation;
• Convective bursts, driven by high SSTs, play an important role in generating the upper-level warm core.
-120
-100
-80
-60
-40
-20
0
20
-120
-100
-80
-60
-40
-20
0
20
0 6 12 18 24 30 36 42 48 54 60 66 72
Pre
ssu
re D
efic
it (h
Pa
)
Time (hour)
380
Hei
gh
t (k
m)
Pre-RI RI Post-RI
A
C
360
340
320
400
B
Shadings: Temperature perturbation with respect to t = 0;
Contours: Potential temperature
Wind barbs
all taken at the eye center.
Total warmingWarming above 380 KWarming below 380 K
a)
b)
380 K
t = 36 h
340 K
vt
z
z
vtsTR
zgzpdzT
R
gzpp
t
b
exp)()exp)( 1
Efficiency of upper level warming
T1+∆T
T2
T1
T2+∆T
21
exp)(
exp)(RT
zg
TTR
zgzpp ta
)(expexp)(
21 TTR
zg
RT
zgzpp tb
))((
))((exp
2121
2121
TTTTTRT
TTTTTzg
p
p
b
a
PaPb
Pt
Hypothesis – upper level warm core
• An upper level warm core is important for RI;• The upper level warm core results from the descending
air in the lower stratosphere due to convective bursts• This upper level warm core is protected by the
symmetric divergent outflow at upper level from ventilation;
• Convective bursts, driven by high SSTs, play an important role in generating the upper-level warm core.
0
10
20
30
40
50
60
70
80
90
100
0
200
400
600
800
1000
0 6 12 18 24 30 36 42 48 54 60 66 72
Mean
Rad
ius of In
tense U
pd
raftsN
um
ber
of
Inte
nse
Up
dra
fts
Model Hour
AE
ERC
0
10
20
30
40
50
60
70
80
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Pre-RIRIPost-RI
Height (km)
Ave
rage
d O
ccu
rren
ces
No. of updraftsMean radius of updraftsRMW (z = 1 km)RMW (z = 11 km)
0
200
400
600
800
1000
0 6 12 18 24 30 36 42 48 54 60 66 72
Nu
mb
er o
f In
ten
se U
pd
raft
s
Model Hour
Pre-RI RI Post-RI
The cloud field at z = 17.5 km and CBs. The red circle is the RMW at z = 1 km
t = 30 h,t = 30.08h
Vertical cross section of cloud hydrometeors (shaded, g kg-1), storm-relative flow vectors, and vertical motion (downward/dashed every 1 m s-1 and
upward/solid every 3 m s-1).
NASA/GSFC, 26 March 2012
Hypothesis – upper level warm core
• An upper level warm core is important for RI;• The upper level warm core results from the descending
air in the lower stratosphere due to convective bursts• This upper level warm core is protected by the
symmetric divergent outflow at upper level from being ventilated;
• Convective bursts, driven by high SSTs, play an important role in generating the upper-level warm core.
400
380
360
340
320
400
380
360
340
320
Hei
ght (
km
)
a
b
Radius (km)
880
900
920
940
960
980
1000
880
900
920
940
960
980
1000
0 6 12 18 24 30 36 42 48 54 60 66 72
• Higher altitude of warm core at t =30 h;• Higher outflow layer at t=30 h;• Higher inflow layer at t=30 h;
ab
t = 30 h
t = 54 h• Warm core is located at the same altitude as the outflow layer
Differences:
Common feature:
50
a) 15:15
W
b) 15:30
c) 15:45 d) 16:00
W
W
W
RI onset
Shading: θ
Red contour:Upward motion
Blue contour:Downward motion
Black circle:RMW at Z = 1 km
“W”: warm anomaly
Z = 14 km
W1
W1
W2
W2W2
a) 11:25 b) 11:40
c) 11:55 d) 12:05
40
Pre-RI
Shading: θ
Red contour:Upward motion
Blue contour:Downward motion
Black circle:RMW at Z = 1 km
“W”: warm anomaly
Z = 14 km
Internal gravity wave movie
Hypothesis – upper level warm core
• An upper level warm core is important for RI;• The upper level warm core results from the descending
air in the lower stratosphere due to convective bursts• This upper level warm core is protected by the
symmetric divergent outflow at upper level from ventilation;
• Convective bursts, driven by high SSTs, play an important role in generating the upper-level warm core.
NASA/GSFC, 26 March 2012900
920
940
960
980
1000
900
920
940
960
980
1000
0 6 12 18 24 30 36 42 48 54 60 66 72
SST-1
CTL
Hei
gh
t (k
m)
Cen
tra
l P
ress
ure
(hP
a)
400
380
360
340
320
400
380
360
340
320
Model Hour
b
a
c
The 18/6/2 km control simulation
The SST-1 sensitivity simulation
CTL: 3.5 hPh/hrSST-1: 1.9 hPa/hr
0
50
100
150
200
0 6 12 18 24 30 36 42 48 54 60 66 72
Nu
mb
er o
f In
ten
se U
pd
raft
s
Time (hour)
2-km control2-km SST-1
Time Series of the number of Intense updrafts
Hypothesis – small symmetric eyewall
• The small eye is important;• The symmetric patter is important
Hypothesis – small symmetric eyewall
• The small eye is important;• The symmetric patter is important
CEN
TRA
L SU
RFA
CE
PRES
SUR
E (
mb)
RA
DIU
S OF M
AXIM
UM
WIN
D (km
)TIME (hours)
0 24 48 72 96 120
Pmin
Rmaxv
1010
1005
1000
995
990
985
180
150
120
90
60
30
0
880
900
920
940
960
980
1000
880
900
920
940
960
980
1000
0 6 12 18 24 30 36 42 48 54 60 66 72
Adapted from Schubert and Hack (1982)
Onset of RI
RMW (km)
DP
(hP
a)
• AAM conservation
• Gradient wind balance
• solid body rotation
Hypothesis – small symmetric eyewall
• The small eye is important;• The symmetric patter is important
Why does the eyewall becomes from asymmetric to symmetric?
40
a) 06:00 b) 15:00
v v v v v v v v v vv
v
v
v
v
v
1
3
5
7
9
11
13
15
13
57
911
13
15
Why symmetric pattern is important for RI?
-25
-15
-5
5
15
25
35
-25
-15
-5
5
15
25
35
3 6 9 12 15 18
1-5 km distancedistance_ydistance_x
Time (hour)
Dis
tan
ce (
km
)
(b) 07:45
(c)08:05 (d)08:45
(a) 07:00
AB
AB
AB B
A
How does the eye size contract fast in pre-RI stage?
Shading: radar reflectivity
contour:Vorticity
“A”, “B” denote the rainbands.
CEN
TRA
L SU
RFA
CE
PRES
SUR
E (
mb)
RA
DIU
S OF M
AXIM
UM
WIN
D (km
)
TIME (hours)0 24 48 72 96 120
Pmin
Rmaxv
1010
1005
1000
995
990
985
180
150
120
90
60
30
0
eyewall closure !Small symmetric eyewall forms!
Conclusion
• WRF model reproduces reasonable well the track, intensity and storm structure given the reasonable configuration;
• An upper level warm core is important for the storm to undergo RI because of its efficiency;
• The upper level warm core results from the descending air in the lower stratosphere due to convective bursts
• This upper level warm core is protected by the symmetric divergent outflow at upper level from ventilation;
• Convective bursts, driven by high SSTs, play an important role in generating the upper-level warm core.
Conclusion -continued
• The small eye size is important in determining RI;• The asymmetric pattern is hostile to RI because it
induces tilting and the asymmetric divergent outflow advects warming away from the center;
• The change of vertical wind shear with time is a key factor for the trigger of RI since it prevents the formation of a large symmetric eyewall at early stage.
Future work
• Perform more clear SST sensitivity tests to identify its impact on convective bursts and associated warm core;
• Microphysics sensitivity test.
Any questions?