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 ）