The Impact of Canonical and Non-canonical El Nino and the Atlantic Meridional Mode on Atlantic Tropical Cyclones

典型和非典型厄尔尼诺现象及大西洋经向模态对大西洋热带气旋的影响

• 批准号: 1347808
• 负责人: Ramalingam Saravanan
• 金额: $ 22.03万
• 依托单位: Texas A&M University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-02-01 至 2018-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1347808&HistoricalAwards=false
• 关键词: Impact; Canonical; Non; canonical; El

This project examines the roles of sea surface temperature (SST) variations in the tropical Atlantic and Pacific on Atlantic Tropical Cyclones (TCs, including hurricanes). The SST variations considered are those associated with two types of El Nino events, the traditional East Pacific (EP) events in which the largest SST warming occurs in the equatorial EP, and the non-traditional Central Pacific (CP) El Nino events in which the maximum warming occurs along the equator near the dateline. In addition, the work will consider the impact of SST anomalies associated with the Atlantic Meridional Mode (AMM), a meridional dipole pattern with warming north of the equator accompanied by cooling south of the equator and vice versa. Previous research associates La Nina events with enhanced Atlantic TC activity while El Nino events are associated with suppression of TCs in the Atlantic, and in particular the PIs estimate that the probability of one or more major hurricanes making landfall on the U.S. coast is 23% during El Nino compared to 63% during La Nina. However, the extent to which these relationships hold for both CP and EP El Nino events has not been determined, and the few studies that have been performed show conflicting results. The AMM is also believed to have an impact on Atlantic TCs, but the mechanism of this influence is not well understood, in part because the AMM modulates several environmental factors that cooperate in their influence on Atlantic TCs. The research tests three specific hypotheses, the first of which posits that the primary influence of the AMM on Atlantic TCs is through the cross-equatorial SST gradient associated with the SST anomalies, which modulates the circulation and thermodynamics of the overlying atmosphere. The second hypothesis is that the geographic difference between CP and EP El Nino events is of less importance than the strength of the SST anomalies, thus CP El Ninos are expected to have a smaller influence than EP events simply because the CP events tend to be weaker. the third hypothesis is that there is constructive interference between La Nina events and positive AMM excursions, so that the combination of two is extremely supportive of Atlantic TCs, while a similar destructive interference between El Nino and negative AMM results in near-average Atlantic TC activity. The bulk of the work for the project consists of numerical experiments using the Weather Research and Forecasting (WRF) model, configured as a Tropical Channel Model (TCM), meaning a re-entrant domain in the zonal dimension with meridional boundaries at 30S and 50N.The work has broader societal impacts due to the potential value of better understanding of relationships between Atlantic TCs and SST variability associated with El Nino and the AMM, which could be used to anticipate how active the Atlantic hurricane season will be in a given year. In addition, the work supports an early-career scientist from a traditionally underrepresented group.

该项目研究热带大西洋和太平洋海面温度（SST）变化对大西洋热带气旋（TC，包括飓风）的作用。 所考虑的海温变化与两种类型的厄尔尼诺事件有关，即传统的东太平洋（EP）事件，其中最大的海温变暖发生在赤道地区，以及非传统的中太平洋（CP）厄尔尼诺事件，其中最大的海温变暖发生在赤道地区。最大变暖发生在日期变更线附近的赤道沿线。 此外，这项工作还将考虑与大西洋经向模态（AMM）相关的海温异常的影响，这是一种赤道以北变暖而赤道以南变冷的经向偶极子模式，反之亦然。 先前的研究将拉尼娜事件与大西洋热带气旋活动的增强联系起来，而厄尔尼诺事件则与大西洋热带气旋的抑制有关，特别是，PI估计，在2017年期间，一次或多次大型飓风在美国海岸登陆的概率为23%。厄尔尼诺现象期间的这一比例为 63%。 然而，这些关系对于中部型厄尔尼诺事件和东部型厄尔尼诺事件的适用程度尚未确定，而且已经进行的少数研究显示了相互矛盾的结果。 AMM 也被认为对大西洋 TC 产生影响，但这种影响的机制尚不清楚，部分原因是 AMM 调节了多个环境因素，这些因素协同影响大西洋 TC。 该研究测试了三个具体假设，第一个假设认为AMM对大西洋TC的主要影响是通过与海温异常相关的跨赤道海温梯度来调节上覆大气的环流和热力学。 第二个假设是，CP 厄尔尼诺事件和 EP 厄尔尼诺事件之间的地理差异不如海温异常的强度重要，因此 CP 厄尔尼诺事件预计比 EP 厄尔尼诺事件的影响更小，因为 CP 厄尔尼诺事件往往较弱。 第三个假设是，拉尼娜事件和正 AMM 偏移之间存在相长性干扰，因此两者的结合极大地支持了大西洋 TC，而厄尔尼诺事件和负 AMM 之间类似的破坏性干扰导致大西洋 TC 活动接近平均水平。 该项目的大部分工作包括使用天气研究和预报 (WRF) 模型进行数值实验，该模型配置为热带通道模型 (TCM)，这意味着在纬向维度上有一个折返域，经向边界位于南纬 30 度和北纬 50 度这项工作具有更广泛的社会影响，因为它具有更好地了解大西洋热带气旋与厄尔尼诺和 AMM 相关的海温变化之间关系的潜在价值，可用于预测大西洋的活跃程度飓风季节将在给定年份。 此外，这项工作还为来自传统上代表性不足的群体的早期职业科学家提供支持。