[A-AS03] [EE] 最新の大気科学：海大陸研究強化年－YMC

[AAS03-P02] Drastic deepening of the barrier layer off the western coast of Sumatra
due to the MJO passage during the Pre-YMC

*茂木 耕作¹、米山 邦夫¹、勝俣 昌己¹、安藤 健太朗¹、長谷川 拓也¹ (1.国立研究開発法人　海洋研究開発機構　大気回用相互作用研究分野)

キーワード：barrier layer, MJO

Drastic deepening of the barrier layer off the western coast of Sumatra
(4°S, 102°E, 800 m depth) due to the MJO passage observed during
December 2015 is investigated. The Research Vessel Mirai observation
captured the drastic increase of isothermal depth from 20 m to 100 m
for only 4 days due to the westerly burst (5-9 m/s) associated with
the MJO. While, the mixed layer was deepened from 10 m to 40 m because
of the strong stratification of the salinity in the ocean surface
layer. As a result, the barrier layer depth was deepened from 10 m to
80 m. This drastic deepening of the barrier layer was associated with
the increase of turbulent energy dissipation rate. Because the current
speed in the surface layer off the western coast of Sumatra was very
slower (less than 20 cm/s) than that over the open ocean (more than 50
cm/s), the vertical mixing due to the westerly burst could be a main
factor for the barrier layer deepening.