Drastic change of barrier layer off Sumatra due to MJO passage
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The document discusses how the barrier layer off the western coast of Sumatra drastically deepened due to the passage of a Madden-Julian Oscillation (MJO) during the Pre-YMC period. The barrier layer thickness increased from 5m to 60m within one day and up to 85m over five days, which had never been observed before. This drastic deepening was caused by vertical mixing from the MJO forcing and downwelling of the thermocline by an oceanic Kelvin wave occurring in phase with the MJO. High-frequency observations are needed to better understand the ocean's response and role in rainfall formation during MJO events.
![light water
heavy water
barrier layer: halocline
depth(m) Salinity(psu)
temperature ( )℃
isopycnic layer depthdepth
isothermal layer depth
ILD( T=0.2 )⊿ ℃
MLD
( [ T=0.2 ])⊿σ ⊿ ℃](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
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Drastic change of barrier layer off Sumatra due to MJO passage
- 1. JAMSTEC/DCOP Qoosaku MOTEKIQoosaku MOTEKI Masaki KATSUMATA Kunio YONEYAMA Kentaro ANDO Takuya HASEGAWA Drastic changeof the barrier layerbarrier layer off the western coastof Sumatra due to the MJO passage during the Pre-YMC
- 2. light water heavy water barrier layer: halocline depth(m) Salinity(psu) temperature ( )℃ isopycnic layer depthdepth isothermal layer depth ILD( T=0.2 )⊿ ℃ MLD ( [ T=0.2 ])⊿σ ⊿ ℃
- 3. Drastic deepening of BL BLT (barrier layer thickness) increased from 5m to 60m within 1-day, up to 85m during 5-days. Such drastic deepening of BL has not observed ever.
- 4. Factors for drastic deepening BLT increased by vertical mixing by MJO forcing and downwelling thermocline by oceanic Kelvin wave. in-phase of MJO and oceanic Kelvin wave
- 5. R/V MiraiR/V Mirai 2015/12/13 00Z MJO observed during R/V Mirai cruise Global-IR
- 6. R/V MiraiR/V Mirai MJO passage westerlywesterly windswinds
- 7. MJO MLDMLD ILDILD BLTBLT depth(m) ILD( T=0.2 )⊿ ℃ MLD ( [ T=0.2 ])⊿σ ⊿ ℃
- 10. downwelling Kelvin wave arrives Sumatra R/V MiraiR/V Mirai
- 11. BL deepeningby vertical mixingwith MJO forcingand stretchingwith downwelling Kelvin wave salinity stratification is stretching bysalinity stratification is stretching by downwelling Kelvin wavedownwelling Kelvin wave breaking fresh lensbreaking fresh lens by vertical mixingby vertical mixing after MJO forcingafter MJO forcing
- 12. depth(m) Salinity(psu) temperature ( )℃ fresh lens before MJO ILD( T=0.2 )⊿ ℃ MLD ( [ T=0.2 ])⊿σ ⊿ ℃ light water heavy water
- 13. light water heavy water barrier layer: halocline depth(m) Salinity(psu) temperature ( )℃ fresh lens breaking by vertical mixing ILD deepening by Kelvin wave ILD( T=0.2 )⊿ ℃ MLD ( [ T=0.2 ])⊿σ ⊿ ℃ after MJO
- 14. Drastic deepening of BL BLT (barrier layer thickness) increased from 5m to 60m within 1-day, up to 85m during 5-days. Such drastic deepening of BL has not observed ever.
- 15. Factors for drastic deepening BLT increased by vertical mixing by MJO forcing and downwelling thermocline oceanic Kelvin wave. in-phase of MJO and oceanic Kelvin wave
- 16. BL formation: Salinity stratification tendency H. adv. V. adv. tilting stretchin g vertical mixing Cronin, M. F., and M. J. McPhaden, 2002: Barrier layer formation during westerly wind bursts. J Geophys Res-Oceans, 107. tendency H. adv. tilting stretching vertical mixing
- 18. depth(m) MJO
- 19. 塩分鉛直傾度 Sz→ 塩分成層の伸縮 -wzSz
- 20. MJO depth(m)
- 22. MJO passagedisturbance passage 35m 35m 20m 25m 25m 10m 60m 70m 85m 100m
- 23. MJO passagedisturbance passage 6m/s 35m 3m/s 35m 5m/s 20m 25m 25m 10m 60m 70m 9m/s 8m/s 85m 100m
- 24. depth(m) Salinity(psu) temperature ( )℃ isopycnic layer depth isothermal layer depth ILD( T=0.2 )⊿ ℃ MLD ( [ T=0.2 ])⊿σ ⊿ ℃
- 25. light water heavy water barrier layer: halocline depth(m) Salinity(psu) temperature ( )℃ isopycnic layer depthdepth isothermal layer depth ILD( T=0.2 )⊿ ℃ MLD ( [ T=0.2 ])⊿σ ⊿ ℃
- 27. downwelling Kelvin wave arrives Sumatra
- 28. The way of ocean response depends on the condition of ocean surface layer
- 29. What ocean response was induced by the MJO forcing?
- 32. 80km80km100km
- 33. 80km80km100km
- 34. High SSTHigh SST (30℃)(30℃) 2015/12/13 00Z SST condition during MJO passage NOAA
- 35. low Sal. (<33psu)low Sal. (<33psu) 2015/12/13 00Z surface salinity during MJO passage ECCO2
- 45. MJO 通過 水深(m) バリアレイヤー層：塩分成層 等温層 ( T=0.2 )⊿ ℃ 等密度層 ( [ T=0.2 ])⊿σ ⊿ ℃
- 55. 塩分鉛直傾度の時間変動 Szt
- 56. 塩分の時間変動 St→ 低塩分の鉛直混合 -(w’S’)zz
- 57. 塩分鉛直 2 階微分 Szz→ 鉛直移流 -wSzz
- 67. 水温 (K: カラー ) MJO 通過 水深(m) 等密度層等密度層 等温層等温層 バリアレイヤー：塩バリアレイヤー：塩 分成層分成層 水深(m)
- 68. 塩分 (psu: カラー ) MJO 通過 水深(m)
- 69. 地表風速 (m/s: 黒実線 ) MJO 通過 水深(m)
- 70. 乱流エネルギー散逸率 ( カラー ) log[ ](W/kg)ε MJO 通過 海洋の鉛直混合の強さ 水深(m)
- 71. 等密度層等密度層 等温層等温層 バリアレイヤー：塩バリアレイヤー：塩 分成層分成層 密度 (kg/m3 : カラー ) MJO 通過 水深(m)
- 72. 低塩分の表層が強風で鉛直混合した結果 、 水温躍層の塩分成層が顕在化して 厚いバリアレイヤーが出現 MJO 通過塩分 (psu) ケルビン波によるケルビン波による 水温躍層・塩分成層の沈降水温躍層・塩分成層の沈降 MJOMJO によるによる 表層の鉛直混合表層の鉛直混合
- 73. 海洋が降水形成に与える影響 MJO の発生・梅雨前線の北進 MJO が海洋表層に与える影響 バリアレイヤーの形成過程 観測現場でのリアルタイムの データ同化システムの構築 実績 5 年計画 10 年展望
- 74. MJO 通過 水深(m) 蛍光度 (fls: カラー )
- 75. MJO 通過 水深(m) 塩分時間変化 (dpsu/dt: カラー )
- 76. MJO 通過 水深(m) 乱流エネルギー変化率 ( カラー ) log[ ](W/kg/day)ε 鉛直混合の強化・弱化
- 77. MJO 通過 水深(m) 乱流エネルギー変化率 ( カラー ) log[ ](W/kg/day)ε 鉛直混合の強化・弱化
Editor's Notes
- My name is Qoosaku MOTEKI. I would like to show here the drastic change process of the ocean surface structure by the MJO forcing. I was on the Research Vessel Mirai cruise to operate this oceanic turbulence observation in December 2015 during the Pre-YMC campaign. So that’s why I do this study.
- First of all, the barrier layer is the difference between the mixed layer depth and isothermal layer depth due to the salinity stratification. The barrier layer prevent to vertically exchange the heat flux and momentum flux. So the barrier layer thickness would be one of the key factors for air-sea interaction.
- On the basis of the Pre-YMC observations, BLT increased drastically within only 24 hours during the MJO passage over the R/V Mirai. Such drastic deepening has not observed ever. what I want to conclude here is,
- Such drastic deepening is due to the vertical mixing by the MJO forcing and downwelling thermocline by oceanic Kelvin wave. The fact that these two factors in the atmosphere and ocean are in-phase is inducing drastic deepening.
- So lets get started with the observed MJO status. Well-organized MJO convection passed over the eastern Indian Ocean on 13 December in 2015.
- taking average of tbb btw 5s-5n, the MJO convection associated with the westerly winds passes during the latter half of the Mirai observation period like this. Remarkable oceanic response is induced by this MJO forcing of the strong westerly winds...
- like this. This is a time-depth cross section of temperature from 3-hourly CTD observation. Mixed layer depth defined from density difference that is equivalent to 0.2degC is shown by dashed line, and isothermal depth defined from 0.2degC temperature difference is shown by dotted line. The blue line of the 29degC shows continuous downwelling thermocline from 23 November to 17 December. Meanwhile, before the MJO arriving on 13 Dec., MLD and ILD are quite shallow and BLT is less than 20 m. Whereas, as the MJO arriving 13 Dec., ILD is rapidly increasing from 20 m to 80 m, but very shallow MLD is keeping less than 20 m. Then, BLT is drastically deepening during the MJO passage. This time lag of deepening of ILD and MLD is due to
- very strong salinity stratification near the surface. Before the MJO, the salinity above 10 m is less than 32 psu that is quite small because of large amount of continuous precipitation everyday. This strong salinity stratification structure near the surface is called fresh lens. We clearly find that the fresh lens structure is broken by the MJO forcing after 13 Dec. So what is the MJO forcing?
- This is time-depth cross section of turbulence energy dissipation rate by color. The bold solid line shows sea surface wind speed with the right axis. The strong wind peaks of the MJO forcing appear twice on 13 and 15 Dec. And vertical mixing signals appear as the oceanic response from the MJO forcing. So this vertical mixing could break the fresh lens structure and the salinity stratification extend downward. This is one of the factors of the drastic deepening of BLT. However, vertical mixing signals don’t sufficiently reach up to the bottom of the ILD. So the downwelling ILD is due to the distinct factor.
- That is downwelling Kelvin wave that just arrives Sumatra. This is time longitude cross section of sea surface height anomaly from ocean objective analysis ECCO2 dataset. The black contours indicate the surface westerly wind speed from the atmospheric objective analysis. You can easily see that positive anomaly of sea surface hight under the westerly winds propagates eastward and arrives Sumatra during the Pre-YMC period.
- So, as the background, continuous downwelling thermocline during the observation period from 20 m to 100 m is due to the oceanic Kelvin wave. Above 20 m, there is a remarkable fresh lens structure before the MJO passage, and the fresh lens is broken by the vertical mixing after 13 December due to the MJO forcing. These two factors induce the drastic deepening of the barrier layer.
- That is, the vertical profile with fresh lens structure before the MJO is drastically changed
- to this one after the MJO because the fresh lens was broken by the vertical mixing due to the MJO forcing and ILD deepening by oceanic downwelling Kelvin wave. As a result, a thick barrier layer appears within 24 hours on 13 December.
- On the basis of the Pre-YMC observations, BLT increased drastically within only 24 hours during the MJO passage over. Such drastic deepening has not observed ever. what I want to conclude here is,
- Such drastic deepening is due to the vertical mixing by the MJO forcing and downwelling thermocline by oceanic Kelvin wave. The fact that these two factors in the atmosphere and ocean are in-phase is inducing drastic deepening.
- Such drastic deepening is due to the vertical mixing by the MJO forcing and downwelling thermocline by oceanic Kelvin wave. The fact that these two factors in the atmosphere and ocean are in-phase is inducing drastic deepening.
- Such drastic deepening is due to the vertical mixing by the MJO forcing and downwelling thermocline by oceanic Kelvin wave. The fact that these two factors in the atmosphere and ocean are in-phase is inducing drastic deepening.
- salinity stratification: vertical derivative of salinity
- fluorescence distribution after the MJO shows a trace as a result of vertical mixing
- This is time series of mixed layer depth by black, isothermal layer depth by blue, and barrier layer thickness by black dashed line, from 23 Nov. to 17 Dec. based on the CTD observation.
- This is time series of mixed layer depth by black, isothermal layer depth by blue, and barrier layer thickness by black dashed line, from 23 Nov. to 17 Dec. based on the CTD observation.
- This is time series of mixed layer depth by black, isothermal layer depth by blue, and barrier layer thickness by black dashed line, from 23 Nov. to 17 Dec. based on the CTD observation.
- ．
- Such drastic deepening is due to the vertical mixing by the MJO forcing and downwelling thermocline by oceanic Kelvin wave. The fact that these two factors in the atmosphere and ocean are in-phase is inducing drastic deepening.
- そこで、そうした取り組みによる直近の実績のポイント
- このように，みらいの観測海域をMJOが通過するところでデータを得る
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- そこで、そうした取り組みによる直近の実績のポイント
- あくまでJAMSTECにしか絶対にできない、そう確実に言える成果を出していく上で、私が担える役割
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．
- それを示す非常に貴重なデータを得ることができました．