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MAHASRI/ HyARC Workshop in Da n ang

MAHASRI/ HyARC Workshop in Da n ang. Internal structure of westward migratory cloud systems with diurnal cycle in west Sumatera observed on 10 November, 2006 during HARIMAU2006 campaign Namiko Sakurai ・ Shuichi Mori (JAMSTEC) ・ Masayuki Kawashima ・

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MAHASRI/ HyARC Workshop in Da n ang

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  1. MAHASRI/HyARC Workshop in Danang Internal structure of westward migratory cloud systems with diurnal cycle in west Sumatera observed on 10 November, 2006 during HARIMAU2006 campaign Namiko Sakurai・Shuichi Mori(JAMSTEC)・Masayuki Kawashima・ Yasushi Fujiyoshi（Hokkaido Univ.）・HAMADA Jun-Ichi（JAMSTEC）・ Hironori Fudeyasu（IPRC）・Yoshikazu Tabata（Kyoto Univ.）・Emrizal（BMG）・ FadliSyamsudin（BPPT）・Manabu D. Yamanaka（JAMSTEC/Kobe Univ.）・ Jun Matsumoto（Tokyo Metro. Univ./JAMSTEC）

  2. Diurnal cycle of cloud system migration over Sumatera Island Satellite data analysis (Yang and Slingo 2001; Mori et al. 2004) 01LST 04LST 16LST 19LST (Sakurai et al. 2005, JMSJ) As a next step, ground based observation is needed. • Internal structure of migratory precipitation system with diurnal cycle. • Three-dimensional wind field structure in the migratory precipitation • system.

  3. Dual Doppler radar observation was held by HARIMAU project in 2006 and 2007 in the West Sumatera ★ HARIMAU2006 ★:Wind profiler ★:Weather radar Objective of this study To describe internal structure of westward migratory cloud system with diurnal cycle using HARIMAU2006 data.

  4. Intensive Observation (HARIMAU2006) Observation period 26 Oct. ～ 27 Nov., 2006 Observation data R=83km ①X-band Doppler Radar (XDR) at MIA and Tiku Time resolution：6 minute Elevation：18 ②Rawinsonde data at Tabingand Siberut Time resolution: 3 or 6hours ③Automatic Weather Station (AWS) at MIA, Tiku, Tabing, and Siberut Time resolution：1 minute

  5. MTSAT IR1 on Nov.10, 2006 NOV.10 14LT NOV.10 16LT NOV.10 18LT NOV.10 20LT NOV.10 22LT NOV.11 00LT

  6. Background wind on November 10, 2006 Horizontal wind at Tabing Tabing ★ N E Zonal wind

  7. Surface wind at Tiku on November 10, 2006 Tiku ★ (°) Sea breeze→Land breeze 360 8 (m/s) 300 6 240 180 4 120 2 60 0 0 24 00 06 12 18 ■：Wind direction ◆：Wind speed Local Time

  8. Time variations of precipitation systems on 10 November, 2006 2km Lake Maniajau Tiku MIA

  9. Migration of precipitation over the land 12:00－16:30LT Lake Maninjau X’ X’ Old convective cell Tiku New convective cell X X X X’

  10. 0.5km in height Tiku Precipitation systems from the land were accompanied with strong easterly wind. MIA Precipitation systems generated over the sea developed northward with southerly wind.

  11. West-southwestward migration After 19:30LT A A’ A’ A Migratory speed: 5 m/s.

  12. 20:24LT B B’ B’ B

  13. Statistical analysis of the number and dimension of precipitation systems during HARIMAU2006 Land Sea [m] 352 52 102 152 202 252 302 402 [km2]

  14. Summary Internal structure of precipitation systems which migrated from the land to the sea off on November 10, 2006 was investigated by dual Doppler radar analysis. Migratory mechanism of precipitation systems The precipitation systems generated new convective cells successively in the region of sea (land) breeze front. Northwestward migration of precipitating systems in the daytime was explained by advection by environmental wind in the lower troposphere. Precipitation systems from the land to the sea off was migrated by successive generation of new convective cells in the leading edge of the precipitation systems. Organization of precipitation systems over the sea Precipitation systems migrating from the land and generating over the sea organized into larger precipitation system than those over the land, and the horizontal scale was more than 100 km in long axis which was on a parallel with the western coast of Sumatera Island.Statistical analysis showed that the number of large precipitation systems over the sea was more than that over the land.

  15. Diurnal variation of horizontal distribution of precipitation systems during HARIMAU2006

  16. Diurnal variation of the number of precipitation systems over the land and sea during HARIMAU2006 Land Sea 52 102 152 202 252 302 352 402 [km2]

  17. Convective activity during HARIMAU2006 Rawinsonde observation TBB Tabing

  18. Eastward migration→Southward migration 16:30－19:00LT 0.5km 2km Tiku Tiku

  19. Trajectory analysis ● ●

  20. MIA ★ 24 00 06 12 18 Tabing ★ ■：Wind Direction ◆：Wind Speed 24 00 06 12 18

  21. Steepest descent method was used to obtain the updated values of u,v,w. Unew = Uold + k・d J/d u Vnew = Vold + k・d J/d v Wnew= Wold+ k・d J/d w The iterative process was continued until a satisfactory solution was found (observational error and mass conservation error are minimized with smoothing out the small-scale variations of u,v,w ). Root Mean Squared Error of wind velocity was less than 1 ms-1

  22. Retreaval of three dimensional wind field using 3-D variational technique (Gao et al., 1999) Cost function Jo : Observation error : Errors due to the misfit between observations and analyses Jd : Weak constraint for : Anelastic mass conservation is satisfied as possible. anelastic mass continuity Js : Smoothness Constraint: Spatial Smoothing for removing small scale noise Jb : Background error : Relaxation to the background (rawinsonde) data

  23. Diurnal cycle of convective activity over Indonesian maritime continent Annual Rainfall Evening rain & Morning rain Mori et al. (2004, MWR)

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