時間： 2010 年 6 月 17 日（星期四）下午 02:00 – 04:30
地點：南京信息工程大學
陳 泰 然
學術副校長 / 臺大講座 / 大氣科學系終身特聘教授
國立臺灣大學

 Three storms formed over Fujian / Guangding, intensified into isolated supercells, splitted and propagated eastward across the Taiwan Strait, made landfall over Taiwan and produced rain, hail, and property damage in Dec. 19,2002.
 Supercell thunderstorms are rare in the subtropics, not reported in open literature south of 25 o N over Southeat
Asia / western North Pacific.
 Northern storm registered a reflectivity of 72 dBZ, the strongest ever observed by any radar in Taiwan.
 A cargo plane crashed with the loss of two pilots near
Penghu Islands late on 19 December as it encountered a hailstorm.
 15 min of hail up to 2 cm in diameter, caused power outage and agriculture damage U.S. $ 6 M.

 To understand the synoptic and mesoscale environment that were favorable for the initiation and intensification of supercell thunderstorms.
 Using a cloud model, with real terrain, analysis data, and no initial thermal perturbation to simulate and diagnose storm structure,
Kinematics, splitting process, and the variation in the mesoscale environment.

(a) 1455 LST (f) 1727 LST (k) 1957 LST
(b) 1525 LST (g) 1754 LST (l) 2027 LST
(c) 1556 LST (h) 1826 LST (m) 2057 LST
(d) 1626 LST (i) 1856 LST (n) 2158 LST
(e) 1656 LST
530 km
(j) 1926 LST
530 km
(o) 2259 LST
530 km
Fujian Lungyen Doppler Radar
0.5
 base reflectivity from 1455 to 2259 LST (every 6 min):
 Three storms were initiated about 80 km inland around 1400
LST near the peaks of local terrain with a NE-SW alignment.
 Each of the three storms had lasted for about 10 h and propagated for over 550 km.

Three primary storms and their tracks:
 The storms on 19 December evolved into three isolated supercells, which exhibited storm splitting and propagated eastward for 550 km to make landfall over Taiwan.

Characteristics of super-cellular thunderstorms:
(a) 1714 LST, N1 (c) 1644 LST, C1 (e) 1754 LST, S1
(b) 1914 LST, N1
Inflow notch
Inflow notch
(d) 1926 LST, C1
Inflow notch
Hook echo
(f) 1832 LST, S1
Inflow notch
Inflow notch
Pendant echo
104 km
Inflow notch
Pendant echo
104 km 104 km
 Radar-observed features gave some indication that the three primary storms were indeed supercells.
 Radial velocity not available from Lungyen radar.

Reflectivity contours from Lungyen and CWB radars (30, 40, 50 dBZ) during 1455-2300 LST
 After formation, the three storms evolved into isolated supercells and each experienced multiple splits.
 The right-movers were usually stronger than leftmovers and traveled eastward rapidly at about
18 m s

1 across the Taiwan
Strait.

2100-2400 LST 19 Dec.
3-h total rainfall (mm)
(a) (b)
Lightning reports (19 Dec.)
Solid dot: hail
 Producd swaths of rain, hail, and property damages.

Surface analysis
0000 UTC (0800 LST) 19 Dec. 2002 1200 UTC (2000 LST) 19 Dec.
 Northerly flow prevailed over much of the East Asia under the control of the Siberian high. A NE-SW-oriented cold front extended from the
Japan area to southern Taiwan.
 The severe thunderstorms on 19 December developed around 1400
LST over southern Fujian / eastern Guangdong, behind the surface cold front in a post-frontal environment

925 hPa at 0000 UTC 19 Dec.
(a)
30

N
850 hPa at 0000 UTC 19 Dec.
(b)
30

N
20

N
110

E 120

E
925 hPa
0800 LST
19 Dec 2002
20

N
110

E 120

E
850 hPa
0800 LST
19 Dec 2002
 As 850 hPa front was farther north of 925 hPa front by 100-
200 km, the surface-based postfrontal cold air over the area of storm development was rather shallow and confined to below 925 hPa in the morning of 19 December 2002.

700 hPa at 0000 UTC 19 Dec.
200 hPa at 0000 UTC 19 Dec.
 Strong vertical shear (700 hPa LLJ near Fujian and Taiwan) associated with the cold front and instability.
 An approaching ULJ at 200 hPa also provided strong shear through deep layers, a factor beneficial to the longevity of supercell storms .

Shantou sounding at 0800 LST 19 Dec.
 The supercells occurred behind a winter cold front which provided a large west-southwesterly vertical wind shear of 6.4

10

3 s

1 at 0-3 km.
 Weak-to-moderate instability (CAPE = 887 J kg

1 ) above the shallow surface cold air.
Low-level bulk shear = 6.4

10

3 s

1

 The supercells occurred over the shallow cold air behind a winter cold front, with a large westsouthwesterly vertical wind shear of 6.4

10

3 s

1 at
0-3 km. This combined with weak-to-moderate instability (CAPE = 887 J kg

1 ) above the shallow surface cold air to yield a favorable environment for supercells.

Manual mesoscale surface analyses
GMS-5 IR cloud imagery
(a) 0800 LST, 19 Dec (c)1400 LST, 19 Dec
(a) 0800 LST 19 Dec. 2002
30N
(a)
110E
20N
120E
(b) 1400 LST 19 Dec. 2002
30N
130E
110E
(b) 1100 LST, 19 Dec
(b)
20N
120E 130E



(d) 1700 LST, 19 Dec
(d)
 Prior to storm initiation, significant daytime solar heating under cloudfree skies occurred over the mountain slopes over the area of storm initiation.
 Daytime upslope winds on both sides of the mountain were observed.

A



B
 T exceeded 20 ° C over mountains while induced upslope winds were about 3-5 m s -1 .
 Three storms all initialed close to the peaks of local topography.

(c)
(a)
(b) (d)
 Significant daytime solar heating occurred over the mountain slopes along the coast of southeastern China, leading to development of local circulation and onshore / upslope winds, resulting in convergence and uplifting.

QuikSCAT Oceanic Winds
(a) 0534 LST, 19 Dec 2002
25

N
20

N
115

E
(b) 1825 LST, 19 Dec 2002
120

E
25

N
 Over the Strait, low-level shear intensified during the daytime of
19 Dec. due to cold air surge.
 Increase in low-level shear produced conditions even more prone to supercell development, three storms became more isolated and reached peak intensity after 1730 LST.
20

N
115

E 120

E


Significant daytime solar heating occurred over the mountain slopes along the coast of southeastern
China, leading to development of local circulation and onshore / upslope winds, resulting in convergence and uplifting.
 The storms reached their maximum strength over the Strait where low-level shear intensified during the day due to cold air surge.

 The CReSS (Cloud Resolving Storm Simulator) model developed at the Hydrospheric Atmospheric Research
Center of NU, Japan (Tsuboki and Sakakibara 2002,
2007).
 This model used in this study (v.2.2) is a nonhydrostatic, fully compressible, cloud-resolving model.
 This model employs a terrain-following vertical coordinate

.
 An explicit bulk cold rain scheme are used without any cumulus parameterization.
 Two experiments were performed:
Grid size
Vertical levels
Initial time
Integration length
Remarks
Run1 1.5 km
Run2 0.5 km
65
63
0800 LST 19
Dec. 2002
1100 LST 19
Dec. 2002
24h
14h
JMA regional analyses as IC / LBCS
Run1 as IC / LBCS without nudging

Summary of CReSS-model configuration.
Run 1
Domain and basic setup
Projection
Grid size (km)
Grid number
Domain size (km)
Topography and SST
Initial and lateral boundary conditions (IC/LBCs)
Initial thermal perturbation
Initial time
Integration length
Output frequency
Model physics
Advection, diffusion
Cloud microphysics
Cumulus parameterization
PBL parameterization
Surface processes
Run 2
Lambert Conformal, center at 118

E, secant at 20

N and 50

N
1.5

1.5

100-475 m
648

450

65
972

675

20.8
0.5

0.5

100-475 m
1584

900

63
792

450

19.85
Real at 0.00833

, and observed at 1
 resolution
JMA regional analyses
(20

20 km, 20 levels, 6 h)
CReSS Run 1 outputs
(30 min)
None
0800 LST
24 h
15 min
1100 LST
14 h
15 or 5 min
4th-order in H/V, 4th-order in H/V
Bulk cold rain scheme (6 species)
None
1.5-order closure with TKE prediction
Energy and momentum fluxes, and shortwave and longwave radiation
Soil model
Numerical methods
Time steps (
 t ,
 
)
Integration method
Number of PEs
41 levels, every 5 cm to 2 m deep
2 s, 1 s 1.5 s, 0.5 s
Filtered leapfrog for
 t (HE-VE), and leapfrog and Crank-Nicolson for
 
(HE-VI)
18 108

Observation:
Tracks of major storms simulated by CReSS:
1.5 Km
 CReSS successfully reproduced the three major storms at the correct time and location, but the southern storm decayed too early over the Taiwan Strait. In both runs, model storms travel about 15

-20
 to the left of the actual storms.
0.5 Km

Comparison between observed and modeled storms:
Split Storm Time of Life cell initiation span
(LST) (h)
Distance Mean direction Size traveled and speed *

40 dBZ
(km) (degree/m s

1 ) (km)
Observation
Model
Run 2
(0.5 km)
Model
Run 1
(1.5 km) n1 c1 s1 h1 h2 i1
I2
N1 by 1425

8.6

570 260

/19.6
15-35 yes
C1 by 1425

8.7
S1 by 1455

8.6
N2
Others
1525 4.3

~2-6

518 268

/17.8

507 271

/17.4
247 215

/19.2
~150-400 ~243

/~17-19
15-35
15-40 yes
<20

15 yes yes
 n1 c1 s1 s2 h1
1200

11.0
1145

12.3
1245 7.0
1600

9.0
1830 4.8
1630

8.5
1730 6.0
1330 10.5
1400 6.0
1400
1530
5.8
9.3
1500 9.0
735
313
324
623
410

633 243

/16.0

692 248

/15.7
278 255

/11.0

391 259

/12.1
237 232

/13.9

575 246

/18.8
377 232

/17.5
248

/18.3
247

/13.1
250

/17.6
227

/18.9
258

/15.4

15 yes
10-20 yes

20 yes
10-25

20

12 yes yes yes
10-20 yes

15

15 yes yes
10-20 yes
10-25 yes
10-15 no
* The 500-700 hPa environmental wind was from 243
 at 18.5 m s

1 (WEA).
 The two experiments produced similar overall results, suggesting that the 1.5-km grid spacing is sufficient even for storm dynamics.



ζ t


S R
  [(v
H
 c)  
H
 w
 ζ
 z
 (ω
H
 
H
)w 
 w
ζ
 z
 F
ζ
(1)
 ω
H
 t
S R
  [(v
H
 c)  
H
] ω
H
 w
 ω
H
 z
 (ω   ) V
H
   (Bk)  F
ωH
(2)
  (Bk) 
R p
 p   T (3)

Storm c1 at 3984 m at 1630 LST:
(a) (d) x

 x x


(b) x
 x

 x

(c)
(e)
(f) x
 x

 x

 The vorticity budget analysis indicates that midlevel updraft rotation arose mainly from the tilting effect, and was reinforced by vertical stretching at the supercell stage.
 Vertical advection tends to cancel with stretching.
 Total
 tendency is mostly positive at updraft centers and thus tends to enhance existing

.

(a)



(b)
 D


C
B
E
A
 Solid dots mark 3 primary storms at 1830 LST.
 Letter A~E indicate the locations of model sounding used.
 Only subtle differences exist between observations and run1 results.

Thermodynamic and shear parameters at points A~E in run1 during 1100 LST 19 to 0200
(a) (d)
LST 20 Dec. 2002
                       

(c)

P
C
P
B
D
D
P
A
P
D

(b)

P
C
P
B
D
D
P
A
        
P
D
 
(e)

P
C
P
B
D
D
P
A
        
P
D
 
(f)

       
P
C
P
B
D
D
P
A

P
D

         
D
D
P
C
P
B
P
A
P
D
P
C
D
D
P
B P
A
P
D
 In addition to the common ingredients of sufficient shear and instability, the evolution of model storms depends heavily on the detailed lowlevel vertical structure of storm environment, which varies horizontally and is linked to the rapid evolution of surface cold air.


