Anomalous intraseasonal events in the thermocline ridge region of Southern Tropical Indian Ocean and their regional impacts
Anomalous intraseasonal events in the thermocline ridge region of Southern Tropical Indian Ocean and their regional impacts
复制标题
南热带印度洋温跃层海脊区域的异常季节内事件及其区域影响
DOI：
10.1029/2011jc007357
复制
发表时间：
2012
影响因子：
--
通讯作者：
C. Gnanaseelan
中科院分区：
文献类型：
--
作者：
A. Jayakumar;C. Gnanaseelan
[1]本研究探讨了印度洋西南部温跃层脊地区强季节内冷却事件的机制。利用海洋环流模式和卫星观测资料，研究了与马登朱利安振荡有关的海气界面和海洋过程。敏感性实验的目的是了解海洋对季节内强迫的反应，特别强调2002年的冷却事件，记录了最强的季节内扰动，在过去的十年观察良好。这一事件的特点是异常的步行者环流在热带印度洋和持续的季节内热通量异常的持续时间比典型的类似事件（但没有任何有利的预处理的海洋基本状态的年际时间尺度）。1996年至2007年的模式热收支分析显示，在2002年的强烈冷却事件与马登朱利安振荡和次表层海洋过程的大气通量之间的相位关系。强对流、短波辐射减少和蒸发增加是造成上层海洋热损失的主要原因，同时对流活动相的传播速度变慢，这支持了较长持续时间强迫的积分。敏感性实验表明，海洋的动力响应，通过夹带在季节内的时间尺度主要控制事件期间的生物反应，与海洋年际变率起次要作用。本研究进一步推测了海洋季节内变化在2002年印度次大陆干旱中的作用。
[1] The present study explores the mechanisms responsible for the strong intraseasonal cooling events in the Thermocline Ridge region of the southwestern Indian Ocean. Air sea interface and oceanic processes associated with Madden Julian Oscillation are studied using an Ocean General Circulation Model and satellite observations. Sensitivity experiments are designed to understand the ocean response to intraseasonal forcing with a special emphasis on 2002 cooling events, which recorded the strongest intraseasonal perturbations during the last well-observed decade. This event is characterized by anomalous Walker circulation over the tropical Indian Ocean and persistent intraseasonal heat flux anomaly for a longer duration than is typical for similar events (but without any favorable preconditioning of ocean basic state at the interannual timescale). The model heat budget analysis during 1996 to 2007 revealed an in-phase relationship between atmospheric fluxes associated with Madden Julian Oscillation and the subsurface oceanic processes during the intense cooling events of 2002. The strong convection, reduced shortwave radiation and increased evaporation have contributed to the upper ocean heat loss in addition to the slower propagation of active phase of convection, which supported the integration of longer duration of forcing. The sensitivity experiments revealed that dynamic response of ocean through entrainment at the intraseasonal timescale primarily controls the biological response during the event, with oceanic interannual variability playing a secondary role. This study further speculates the role of oceanic intraseasonal variability in the 2002 droughts over Indian subcontinent.