A Modeling Study of Easterly Waves and Their Intraseasonal Variability in the East Pacific

东太平洋东波及其季节内变化的模拟研究

• 批准号: 1735978
• 负责人: Eric Maloney
• 金额: $ 36.03万
• 依托单位: Colorado State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-11-01 至 2022-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1735978&HistoricalAwards=false
• 关键词: Modeling; Study; Easterly; Waves; Their; Modeling; Study; Easterly; Waves; Their

Easterly waves (EWs) are wavelike atmospheric disturbances with a ridge-to-trough size of roughly 1,000km which propagate from east to west at low latitudes. EWs are important weather makers in much of the tropics and play a critical role in hurricane development. Much of the research has focused on African EWs, which along the easterly jet over the Sahel and propagate westward over the North Atlantic. The genesis of these waves is often explained in terms of jet instabilities particular to the easterly jet, yet similar EWs are found in the tropical eastern Pacific where the large-scale flow characteristics are very different. One explanation for the presence of EWs in the eastern equatorial Pacific is that they originated as African EWs, formed through processes associated with the African easterly jet, and subsequently propagated across the Atlantic and the Caribbean to reach the eastern Pacific. While there is some evidence to support this theory, previous work by the PI (see AGS-1347738) suggests that EWs can form in the tropical eastern Pacific despite the clear differences between this region and the Sahel.This project tests the hypothesis that east Pacific EWs are largely caused by upscale growth of topographically-generated disturbances downwind of the mountain ranges of Central America. Numerical simulation by the PI have shown that EW activity is dramatically reduced when the Central American topography is flattened, but these simulations were crude as the removal of topography has a variety of dramatic effects on the meteorology of the region including mean flow, cloudiness and precipitation. Simulations to be performed here would use a "nudging" technique to constrain the background flow despite modifications to topography and other factors so that a more focused study of wave generation by specific forcing mechanisms can be performed in a realistic setting. The work would use the Weather Research and Forecasting (WRF) model in a convection-permitting configuration. The work would also address the modulation of EWs by intraseasonal oscillations of the background flow. Additional work uses diagnostic techniques including vorticity and energy budgets to study EW generation and propagation in observational data.The work has societal relevance due to the key role of EWs in tropical meteorology and hurricane genesis. If EWs found in the eastern Pacific originated in the African easterly jet they may be more predictable than if they are generated locally by Central American topography, thus the results of this work have potential implications for operational forecasting. The modulation of EW activity by intraseasonal oscillations is also of practical interest given the long lead times of intraseasonal oscillations. In addition, the project provides support and training for a graduate student, thereby providing for the future workforce in this research area.

海浪（EWS）是波浪状的大气干扰，山脊到槽的尺寸约为1,000公里，在低纬度地区从东到西传播。 EWS是许多热带地区重要的气象制造商，并且在飓风发展中起着至关重要的作用。 许多研究都集中在非洲EWS上，非洲EWS沿着萨赫勒的东方喷气式飞机，并在北大西洋上向西传播。 这些波的起源通常用与东方射流的射流不稳定性来解释，但是在热带东部太平洋中发现了类似的EW，在大规模的流动特征非常不同。 在东部赤道太平洋中存在EWS的一种解释是，它们起源于非洲EWS，是通过与非洲东部喷气式飞机相关的过程形成的，随后在大西洋和加勒比海地区传播到东太平洋。 尽管有一些证据可以支持这一理论，但PI先前的工作（参见AGS-1347738）表明，尽管该地区和Sahel之间存在明显差异，但EWS仍可以在热带东部太平洋中形成，但该项目检验了以下假说，即东太平洋EWS在很大程度上是由众多山上散发出山上的山顶上的山上的山顶上的众多山上的增长造成的。 PI的数值模拟表明，当中美洲地形被扁平时，EW活性会大大降低，但是这些模拟是粗略的，因为地形的去除对该地区的气象学有多种巨大影响，包括平均流动，云彩和沉淀。 尽管对地形和其他因素进行了修改，但在此处进行的模拟将使用“淡淡的”技术来限制背景流程，以便可以通过特定的强迫机制进行对波产生的更为专注的研究。 这项工作将在对流的配置中使用天气研究和预测（WRF）模型。 这项工作还将通过背景流的季节内振荡来解决EWS的调节。 其他工作使用诊断技术在内，包括涡度和能源预算在观察数据中研究EW的产生和传播。由于EWS在热带气象学和飓风Genesis中的关键作用，该工作具有社会相关性。 如果在东太平洋地区发现的EWS起源于非洲东部喷气式飞机，它们可能比中美洲地形在本地生成的情况更为可预测，因此这项工作的结果对运营预测具有潜在的影响。 考虑到季节内振荡的长时间，季节内振荡对EW活性的调节也引起了实际兴趣。 此外，该项目为研究生提供了支持和培训，从而为该研究领域的未来劳动力提供了支持。