Investigation of Ningaloo Nino - The Role of Madden-Julian Oscillation and Leeuwin Current Variability

在2010-2011年强烈的拉尼娜现象期间，观察到澳大利亚西海岸出现极端海洋变暖和海洋热浪。这一极端变暖事件被称为“宁格罗厄尔尼诺”，类似于太平洋的厄尔尼诺和大西洋的本格拉厄尔尼诺等其他东部大陆边界变暖现象。在最近的宁格鲁厄尔尼诺事件期间，澳大利亚西海岸的SST比长期季节平均值高出5摄氏度以上，足以影响大规模的大气环流，对海洋生态系统和资源产生破坏性影响。在该区域，东南印度洋的本地和远程强迫海洋环流，如Leeuwin流系统，可能在Ningaloo Niño事件的发展中起着关键作用。这个拟议项目的主要目标是了解控制Ningaloo Niño/Niña发展的物理过程。拟议的项目将有助于规划和设计重大国际实地活动，改善印度洋的观测网络，通过支持学生和博士后加强教育，并推进气候预测。其中一个PI机构被美国教育部认定为西班牙裔服务机构，因此该项目将有助于为代表性不足的少数民族提供培训机会。此外，拟议的研究将确定必须在气候模型中很好地表示的关键过程，这将有助于改善气候模型模拟，并通过提供更可靠的气候预测造福社会。在拟议的研究中，将探讨各种影响“宁格罗厄尔尼诺”的海洋过程，包括：1）来自太平洋的远程强迫与印度洋强迫对Leeuwin海流系统和宁格罗厄尔尼诺/厄尔尼诺的影响; 2）向西辐射的Rossby波的地形捕获效应及其与宁格罗厄尔尼诺/厄尔尼诺事件相关的下降流/上升流; 3）MJO通过海洋过程对Leeuwin海流和Ningaloo Niño/Niña的影响; 4）澳大利亚夏季风在影响Ningaloo Niño/Niña事件中的作用。将采用一个高分辨率的印度洋-太平洋海盆海洋环流模式，该模式可充分反映印度尼西亚海域复杂的水深和地形。将彻底分析和最大限度地利用增强的实地观测数据和卫星数据来验证模型。将进行一系列面向过程的OGCM实验，以量化远程本地强迫对Leeuwin海流系统和Ningaloo/Niño的影响，并确定所涉及的关键过程，包括沿海开尔文波和Rossby波辐射的作用。研究结果将确定确定与Ningaloo Niño相关的海洋表面温度和海洋上层变化的物理过程，这可能会改变大气环流。特别是，Madden-Julian振荡和来自太平洋的远程强迫对Leeuwin海流系统和Ningaloo Niño的影响，不能仅通过观测来隔离，将通过一系列OGCM实验来量化。因此，拟议项目的完成将大大提高我们对Leeuwin海流系统和Ningaloo Niño动力学的理解，这是东南印度洋的主要气候变化。

During the strong La Niña event in 2010-2011, extreme ocean warming and a marine heat wave off the west coast of Australia were observed. This extreme warming event is termed as "Ningaloo Niño", an analogy to other eastern continental boundary warming phenomena such as El Niño in the Pacific and the Benguela Niño in the Atlantic. During the recent Ningaloo Niño event, SSTs off the west coast of Australia were more than 5 degree centigrade above long-term seasonal means, which is sufficient to impact large-scale atmospheric circulation and has devastating impacts on marine ecosystems and resources. In this region, locally and remotely forced ocean circulations in the southeast Indian Ocean, such as Leeuwin current system, may play a crucial role in the development of the Ningaloo Niño event. The primary goal of this proposed project is to understand physical processes that control the development of Ningaloo Niño/Niña. The proposed project will contribute to the plan and design of major international field campaigns and improving observational network in the Indian Ocean, enhancing education through supporting students and a post-doc, and advancing climate prediction. One of the PIs' institutions is recognized as a Hispanic Serving Institution by the U.S. Department of Education, and thus the project will contribute to providing training opportunities for underrepresented minorities. In addition, the proposed research will identify key processes that must be represented well in climate models, which will help improve climate model simulation and benefit society by providing more reliable climate prediction. A variety of oceanic processes that affect the 'Ningaloo Niño' will be explored in the proposed study including: 1) The impact of the remote forcing from the Pacific Ocean versus forcing over the Indian Ocean on the Leeuwin current system and Ningaloo Niño/Niña; 2) Effects of topographic trapping of westward radiating Rossby waves and their associated downwelling/upwelling associated with Ningaloo Niño/Niña events; 3) The influence of the MJO on Leeuwin current and Ningaloo Niño/Niña via oceanic processes; 4) The role of Australian summer monsoon in affecting the Ningaloo Niño/Niña events. A high-resolution Indo-Pacific basin ocean general circulation model (OGCM) will be employed, which can adequately represent complex bathymetry and topography in the Indonesian Seas. The data from enhanced in-situ observations and satellite data will be thoroughly analyzed and maximally utilized to validate the model. A series of process-oriented OGCM experiments will be performed, to quantify the impacts of remote & local forcing on the Leeuwin current system and Ningaloo/Niño, and identify key processes involved, including the role of coastal Kelvin waves and radiation of Rossby waves. The results will identify the physical processes that determine the sea surface temperature and upper-ocean variability associated with Ningaloo Niño, which can alter atmospheric circulations. In particular, the impacts of Madden-Julian oscillation and the remote forcing from the Pacific on the Leeuwin current system and Ningaloo Niño, which cannot be isolated by observations alone, will be quantified by a series of OGCM experiments. Consequently, completion of the proposed project will substantially advance our understanding of the dynamics of Leeuwin current system and Ningaloo Niño that is major climate variability in the southeast Indian Ocean.