Diurnal Convection Peaks over the Eastern Indian Ocean off Sumatra during Different MJO Phases
Diurnal Convection Peaks over the Eastern Indian Ocean off Sumatra during Different MJO Phases
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DOI：
10.2151/jmsj.2011-a22
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发表时间：
2011
影响因子：
3.1
通讯作者：
M. Fujita;K. Yoneyama;S. Mori;T. Nasuno;M. Satoh
中科院分区：
文献类型：
--
作者：
M. Fujita;K. Yoneyama;S. Mori;T. Nasuno;M. Satoh
研究了苏门答腊岛外印度洋东部海域Madden-Julian振荡（MJO）不同阶段的日对流峰值特征。在惠勒和亨登（2004）定义的MJO第2至第3阶段（P2和P3）期间，当印度洋东部上空以中等低空西风为主时，卫星观测到对流的显著日变化。周日的对流峰值在傍晚时出现在苏门答腊岛上空，而对流则在清晨朝印度洋方向迁移。通过在苏门答腊岛西部近海使用全球定位系统，观测到从傍晚到午夜水汽显著减少，抵消了岛上的上升运动。午夜到清晨，对流从海岛向外迁移，使西部近海水汽增加。这一显著的日变化证实了Miura等人（2007）利用非静力ICosahe-Werner大气模式（NICAM）进行的数值试验的结果：在P2-P3期间，东印度洋大气中含有丰富的水汽，而海洋大陆在平静条件下受到太阳辐射的加热。这种情况与两个日对流高峰的发展是一致的：由太阳辐射加热引起的陆地上空傍晚对流和由低层西风和陆风辐合引起的海洋上空午夜对流。
The authors investigated diurnal convection peak characteristics over the eastern Indian Ocean off the island of Sumatra during different phases of the Madden-Julian oscillation (MJO). During MJO phases 2 to 3 (P2 and P3) defined by Wheeler and Hendon (2004), prominent diurnal variation in convection was observed by satellites when moderate low-level westerly winds were dominant over the eastern Indian Ocean. The diurnal convection peaks were prominent over the island of Sumatra in the evening, while migrations of the convection toward the Indian Ocean were observed in the early morning. By using the Global Positioning System around the western region offshore of Sumatra, a significant reduction in water vapor was observed from evening until midnight, compensating for the upward motion over the island. During midnight to early morning, the water vapor in-creased in the western offshore region as the convections migrated from the island. This prominent diurnal varia-tion confirmed the result from a numerical experiment by Miura et al. (2007) using the Nonhydrostatic ICosahe-dral Atmospheric Model (NICAM).During P2 to P3, the atmosphere over the eastern Indian Ocean contains abundant water vapor, while the Maritime Continent is fairly well heated by solar radiation under calm conditions. This situation should be favor-able for the development of two diurnal convection peaks: the evening convection over the land induced by solar radiative heating and the midnight convection over the ocean triggered by convergence of the low-level westerly wind and the land breeze.