Structure and Formation Process ofan Orographic Line-shaped Rainfall System during Baiu Season in Western Kyushu, Jap
an
Ayako Nakamura, Hiroshi Uyeda,(HyARC, Nagoya University, Nagoya, Japan)
Osamu Morita, (Graduate School of Sciences, Kyushu University, Fukuoka, Japan)
Yasufumi Kitazaki, Hideki Beppu(Fukuoka District Meteorological Observatory, JMA, Fukuoka, Japan)
Three rainbands in Kyushu
Goto Islands
Isahaya line1997/07/11/16:00JST
2002/07/01/12:20JSTKoshikijima line
2001/06/19/11:30JSTGoto line
Nagasaki Peninsula
Koshikijima Islands
Max crest : 461m
Max crest : 569m
Max crest : 511mJapan
Kyushu
Sapporo
Z=2.0km
Objective
2001/06/19/11:30JSTGoto lineHow do these lines form
from islands with low mountainsin moist lower atmosphere?
→many analyses・ Goto line
→few analyses
Study on formation mechanism・ Isahaya line and Koshikijima line
PURPOSETo clarify 1. the structure of the 19 June 2001 Goto line 2. the formation process of the 19 June 2001 Goto line
→many analyses・ Goto line
→few analyses
Study on formation mechanism・ Isahaya line and Koshikijima line
observation sites
JapanKyushu
Hirado Fukuoka
SefuriyamaGoto Islands
the Sefuriyama radar data(the JMA operational radar)
upper-air soundings data(at Fukuoka)
JMA wind profiler data(at Hirado)
Meso Regional Analysis data
Sapporo
Environmental field
Relative Humidity at surfaceconvectivelyunstable
780m LCL
RH > 80%at surface
( by MANAL data)
behavior and horizontal structure
Sefuri Mts.
11:40
12:50
09:40
16:00
north ofSefuri Mt
s.
overSefuri Mts.
overSefuri Mts.
dissipation
cellularstructure
north ofSefuri Mt
s.11:40
12:50
09:40
16:00
north ofSefuri Mt
s.
overSefuri Mts.
overSefuri Mts.
dissipation
130 ~ 200km
Sefuri Mts.
Z=2.0km
16:00
overSefuri Mts.
Z=2.0km
Sefuri Mts.Sefuri Mts.
11:40
north ofSefuri Mt
s.
overSefuri Mts.12:50
dissipation
overSefuri Mts.
16:00
Vertical structure
09:40 ~ 11:40
11:40 ~ 12:50
Sefuri Mts.
Distance from Sefuriyama radar site [km]
north ofSefuri Mt
s.
overSefuri Mts.
11:40
12:50
09:40
Wind profile and Froude number
25 ~ 29m/s
Froude number
Fr = 4.8 ( > 1 ) Upslope forcing by Goto Islands
By Smolarkiewicz and Rotunno(1989)
NhUFr 0
h: top height of a mountain
U0: a uniform horizontal windN: Brunt-Vaisala frequency
generation of convective clouds
U0=15m/s , N=6.8×10-3/s , h=460m
Wind Profiler
MANAL09JST
19 JUNE 2001
convective cells
Distance from Sefuriyama radar site [km]
about 28m/s
northeastward
Summary
over no high-mountains over mountains ( >1km height)
upslopeforcing
Weather map at surface
cloud image of GMS-5
Comparison of other lines
Isahaya line1997/07/11/16:00JST
2002/07/01/12:20JSTKoshikijima line
2001/06/19/11:30JSTGoto line
(By Takeda et al. 1999)
(By Nakamura et al. 2002)
Horizontal Feature
16:00
north ofSefuri Mt
s.
overSefuri Mts.
11:40
12:50
09:40
Vertical Feature
11:30
Time variation
Z=2kmZ=6kmZ=10km
Isahaya line
Takeda et al. 1999
Koshikijima line
-4 0 -3 0 -2 0 -1 0 0 1 0 2 0 3 0 4 0
D IS TA N C E E A S T O F N A G A S H IM A ( k m )
1 .0 k m
1 2 3 0 J S T 0 1 J U LY 2 0 0 2
Nakamura et al. 2002
Froude numberFroude numbe
rBy Smolarkiewicz and Rotunno(1989)
NhUFr 0
h: top height of a mountain
U0: a uniform horizontal windN: Brunt-Vaisala frequency
horizontal detouring the obstacle
the vertically propagating-wave pattern
Small Fr ( <1 )Large Fr ( >1 )