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AGS-PRF: Direct Radiative Effects of Saharan Dust on the Dynamics of the African Easterly Jet and African Easterly Waves

AGS-PRF：撒哈拉沙尘对非洲东风急流和非洲东风波动力学的直接辐射影响

基本信息

批准号：
1524767
负责人：
Dustin Grogan
金额：
$ 8.6万
依托单位：
Grogan Dustin F
依托单位国家：
美国
项目类别：
Fellowship Award
财政年份：
2015
资助国家：
美国
起止时间：
2015-10-01 至 2018-01-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1524767&HistoricalAwards=false
关键词：
AGS PRF Direct Radiative Effects

项目摘要

The large-scale atmospheric circulation over North Africa during summer is characterized by three striking features: the African easterly jet (AEJ); African easterly waves (AEWs); and large plumes of Saharan mineral dust aerosols. The central objective of this research is to determine the effects of Saharan dust on the linear dynamics and nonlinear evolution of the AEJ-AEW system. To achieve this objective, several tasks that will be carried out to answer the following questions: Can dust-radiative heating destabilize an otherwise stable AEJ (or vice versa)? If so, what aspects of the dust - concentration, spatial gradients, emission variability, etc. - affect the linear stability of the AEJ? How does the dust physics manifest in terms of the spatial structure and energetics of the AEJ? Are there particular locations and combinations of dust concentration and distribution that will optimize the linear growth (or decay) of AEWs? As the AEWs grow to finite amplitude, how does the dust affect their structure? Are there particular locations and combinations of dust concentration and distribution that will optimize the development of AEWs? And how does the AEJ-AEW system respond to a time varying dust plume, one that varies either periodically or episodically?To answer these questions, and others, the Weather Research and Forecasting (WRF) model, which is coupled to a dust tracer model, will be used to run a systematic sequence of experiments with and without dust. The data from the simulations will be analyzed and compared using standard methods. The analyses will provide information on the effects of dust on the following: growth rate, propagation, and structure of AEWs; formation of critical layers, which have been shown to play a role in tropical cyclogenesis; and local and global energetics of the AEJ-AEW system.Intellectual Merit:The intellectual merit of the research includes: advancing understanding of how Saharan dust-radiative feedbacks, which depend on a combination of the dust concentration and its spatial distribution, affect the linear growth and nonlinear development of AEWs; developing insights into the relationship between the spatial-temporal variability of Saharan mineral dust and the spatial-temporal evolution of the AEJ and AEWs; and improving forecasts of the dust-modified AEJ-AEW system and its possible effects on tropical cyclogenesis over the Atlantic Ocean.Broader Impacts:The broader impacts of this work includes: advancing knowledge on the sensitivity of AEJ-AEW system to the dust plume properties (e.g., location, concentration, spatial gradients), which could aid in the prediction of AEWs and thus tropical cyclones; demonstrating the importance of dust radiative heating on AEWs, which could motivate future studies to examine dust radiative effects on other synoptic scale disturbances that are associated with the dust source regions around the world.

北非夏季大尺度大气环流有三个显著特征：非洲东风急流（AEJ）、非洲东风波（AEWs）和撒哈拉矿物尘埃气溶胶的大羽流。这项研究的中心目标是确定撒哈拉沙尘对AEJ-AEW系统的线性动力学和非线性演化的影响。为了实现这一目标，几个任务，将进行回答以下问题：灰尘辐射加热不稳定，否则稳定的AEJ（反之亦然）？如果是这样的话，尘埃的哪些方面-浓度，空间梯度，排放变化等-影响AEJ的线性稳定性？尘埃物理学如何在AEJ的空间结构和能量学方面表现出来？是否有特定的位置和粉尘浓度和分布的组合，将优化AEW的线性增长（或衰减）？当AEW增长到有限振幅时，尘埃如何影响它们的结构？是否有特定的位置和粉尘浓度和分布的组合，将优化AEW的发展？ AEJ-AEW系统如何响应随时间变化的尘埃羽流，这种尘埃羽流是周期性变化的还是间歇性变化的？为了回答这些问题，以及其他问题，天气研究和预报（WRF）模型，这是耦合到一个灰尘示踪剂模型，将被用来运行一个系统的实验序列有和没有灰尘。将使用标准方法对模拟数据进行分析和比较。这些分析将提供关于尘埃对下列方面影响的资料：AEW的增长率、传播和结构;临界层的形成，这已被证明在热带气旋生成中发挥作用; AEJ-AEW系统的局部和全球能量学。进一步了解撒哈拉地区的沙尘辐射反馈，它取决于沙尘浓度及其空间分布的组合，如何影响AEW的线性增长和非线性发展;深入了解撒哈拉矿尘的时空变化与AEJ和AEW的时空演变之间的关系;改进经灰尘修正的AEJ-AEW系统的预报及其对大西洋上空热带气旋生成的可能影响。更广泛的影响：这项工作的更广泛的影响包括：这些结果表明，沙尘辐射加热对沙尘暴的重要性，这将促使今后的研究考察沙尘辐射对与世界各地沙尘源区有关的其他天气尺度扰动的影响。