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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: fude@bosai.go.jp. 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)

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インドシナ半島に影響を及ぼす熱帯低気圧

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  1. 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: fude@bosai.go.jp

  2. 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

  3. 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

  4. インドシナ半島に上陸する熱帯低気圧のトラック(1990-1998)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

  5. Conclusion August September NE W W October November Upper-level High Upper-level High E E W

  6. The tracks of tropical cyclones landing on the Indochina Peninsula N-course ○ Jul. - Sep. × Oct. - Nov. S-course 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: • The change in the tracks of the tropical cyclones from the N-course to the S-course • The characteristics of N-course and S-course tropical cyclones.

  7. Model Description of the CGCM High-resolution coupled atmosphere-ocean general circulation model Atmospheric component Ocean component JMA (Japan Meteorological Agency) Global Spectral Model Southampton - East Anglia SEA ・・Resolution・・ 0.5625deg, with 37 vertical levels Hydrostatic equation ・・Resolution・・ T213 (with horizontal resolution of 55 km ) with 21 levels in vertical. ・・Scheme・・ Pacanowski and Philander (1981) ・・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) ・・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).

  8. The tracks of simulated cyclones landing on the Indochina Peninsula N-course ○ Jul. - Sep. × Oct. - Nov. S-course 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.

  9. Model Description of the MM5 PSU/NCAR Mesoscale Model 5 version 3 Nonhydrostatic version Domain 1 ・・Initial and boundary condition・・ The 6-hourly outputs of a CGCM including SST Domain 2 ・・Scheme・・ Microphysics Simple Ice scheme Cumulus Grell scheme(D1) Non (D2) PBL MRF scheme Radiation 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.

  10. Tropical cyclones simulated by the MM5 N-course S-course Figure: time variations of central sea level pressure of each tropical cyclone (colors are defined by the course as shown in left figure). Figure: Simulated tracks of the tropical cyclones detected by minimum sea level pressure. Circles indicate the location of 00 and 12 UTC. • Comparing with the S-course cyclone, the N-course cyclone more intensify into the tropical cyclone passing over the northern South China Sea.

  11. Summary About the situation affecting the N-course and the S-course tracks of the tropical cyclones During Jul.-Sep., the existence of the westerly monsoon over the southern part of the Indochina Peninsula intercepts from the tropical cyclones passing the S-course. N-course cyclone 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

  12. Mid-level moisture advection N-course cyclone S-course cyclone N-course cyclonescontinuously move westward even after they landed on the Indochina Peninsula. Summaryabout general characteristics of the N-course and the S-course cyclones S-course cyclonesdecay 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.

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