インドシナ半島に影響を及ぼす熱帯低気圧

インドシナ半島に影響を及ぼす
熱帯低気圧
筆保弘徳飯塚聡松浦知徳
National Research Institute for Earth Science and Disaster Prevention
3-1, Tennodai, Tsukuba, Ibaraki, Japan
E-mail: [email protected]
研究の流れ
事例解析(1998)
・日雨量観測値 GMS5(IR-1) NCEP Reanalysis (2.5deg.)
統計解析気候値
・ NCEP Reanalysis (2.5deg., 1961-1999)
・NASA storm track (1961-1998)
数値シミュレーション
・High-resolution coupled atmosphere-ocean
general circulation model
・PSU/NCAR MM5v3
モンスーン末期(9-11月)の降雨の特徴
• 対流圏下層の西風と北東風・東風との低
気圧性シア域
• 南シナ海・西太平洋からやってくる熱帯低
気圧
• 対流圏上層の偏西風と偏東風との高気圧
性シア域
インドシナ半島に上陸する熱帯低気圧のトラック
(1990-1998)
8,9
10,11
Conclusion
August
September
NE
W
W
October
November
Upper-level High
Upper-level High
E
E
W
The tracks of tropical cyclones landing on the Indochina Peninsula
N-course
○
Jul. - Sep.
S-course
×
Oct. - Nov.
Figure: The tracks of tropical cyclones landing on the Indochina Peninsula for 9 years (1990-1998). Tracks and
generation location of tropical cyclones during July and September (thin line and circle), and tropical cyclones during
October and November (dashed line and cross).
•The tropical cyclones land on Indochina Peninsula mostly from September to November.
•The tropical cyclones tend to pass over the northern part from July to September, while over the
southern part from October to November.
Remarkable points:
1.
The change in the tracks of the tropical cyclones from the N-course to the S-course
2.
The characteristics of N-course and S-course tropical cyclones.
Model Description of the CGCM
High-resolution coupled atmosphere-ocean general circulation model
Atmospheric component
JMA (Japan Meteorological Agency)
Global Spectral Model
Hydrostatic equation
Ocean component
Southampton - East Anglia SEA
・・Resolution ・・
・・Resolution ・・
0.5625deg, with 37 vertical levels
T213 (with horizontal resolution of 55 km )
with 21 levels in vertical.
・・Scheme・・
・・Physical Scheme・・
Short Wave Radiation (Lacis and Hansen, 1974)
Long Wave Radiation (Sugi et al., 1990)
Convection (Arakwa and Schubert, 1974)
SiB (Sato et al., 1989)
Gravity wave drag (Iwasaki et al., 1989)
Pacanowski and Philander (1981)
・・Coupled Model・・
The atmospheric and oceanic
models were coupled through daily
mean SST and atmospheric fluxes.
・・Run・・
Integrated for 14 years (results of the last 11 years).
The tracks of simulated cyclones landing on the Indochina Peninsula
N-course
○
Jul. - Sep.
S-course
×
Oct. - Nov.
Figure: The tracks of tropical cyclones landing on the Indochina Peninsula for 11 years simulated by the CGCM.
Tracks and generation location of tropical cyclones during July and September (thin line and circle), and tropical
cyclones during October and November (dashed line and cross).
•As same in the observations, the simulated tropical cyclones also tend to pass over the
N-course or the S-course, which is in good agreement with the observational evidence.
Model Description of the MM5
PSU/NCAR Mesoscale Model 5 version 3
Nonhydrostatic version
・・Initial and boundary condition・・
The 6-hourly outputs of a CGCM
including SST
Domain 1
Domain 2
・・Scheme・・
Microphysics
Cumulus
PBL
Radiation
Simple Ice scheme
Grell scheme(D1) Non (D2)
MRF scheme
Cloud-radiation scheme
A one-way interactive nested grid
Domain 1(outer):150x150x23(27km)
Domain 2(inner):301x301x23 (9km)
・・Run・・
N-course cyclone :3 case
S-course cyclone :3 case
Figure:Simulated domains and terrain height
above sea level.
Tropical cyclones simulated by the MM5
N-course
S-course
Figure: Simulated tracks of the tropical cyclones
detected by minimum sea level pressure. Circles
indicate the location of 00 and 12 UTC.
Figure: time variations of central sea level pressure
of each tropical cyclone (colors are defined by the
course as shown in left figure).
•Comparing with the S-course cyclone, the N-course
cyclone more intensify into the tropical cyclone
passing over the northern South China Sea.
Summary
About the situation affecting the N-course and the S-course tracks of the tropical cyclones
During Jul.-Sep.,
N-course cyclone
the existence of the westerly monsoon
over the southern part of the Indochina
Peninsula intercepts from the tropical
cyclones passing the S-course.
Cyclone track
High SST region
Westerly wind region
During Oct.-Nov.,
the westerly monsoon disappears,
and SST cooling in the South China Sea
results from the northeast monsoon,
leading to an increase of the S-course
tropical cyclones.
S-course cyclone Northeasterly wind region
Low SST region
High SST region
Cyclone track
Summary about general characteristics of the N-course and the S-course cyclones
N-course cyclones continuously move westward even after they landed on
the Indochina Peninsula.
S-course cyclones decay before moving into Thailand.
During the passage of N-course cyclones over the Indochina Peninsula, the
southeasterly winds associated with the mid-level cyclonic circulation spread
rainfall widely over the northern part of the Thailand.
Mid-level
moisture
advection
S-course
cyclone
N-course
cyclone

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