| 项目编号: | 1560844
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| 项目名称: | Extratropical Persistent Anomalies on a Warmer Earth: Connections to Extratropical Storms and Storm Tracks |
| 作者: | Walter Robinson
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| 承担单位: | North Carolina State University
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| 批准年: | 2016
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| 开始日期: | 2016-09-01
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| 结束日期: | 2019-08-31
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| 资助金额: | 971912
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| 资助来源: | US-NSF
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| 项目类别: | Standard Grant
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| 国家: | US
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| 语种: | 英语
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| 特色学科分类: | Geosciences - Atmospheric and Geospace Sciences
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| 英文关键词: | pas
; project
; condensational heating
; pa
; persistent anomaly
; synoptic system
; study
; climate model
; simulation
; block
; case
; pa behavior
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| 英文摘要: | This is a study of persistent anomalies (PAs) in atmospheric circulation, defined as unusual states of the atmospheric flow that remain approximately fixed over periods longer than a few days. PAs addressed here occur in middle latitudes when the normal eastward progression of weather systems over a given location is disrupted. They are generally associated with splitting or meridional shifting of jet streams and are loosely synonymous with atmospheric blocking, although blocking has a more restrictive definition. Interest in PAs comes largely from their association with high-impact weather events including cold air outbreaks, droughts, pluvials, and heat waves. The project seeks to understand the fundamental dynamics which determine the frequency, intensity, and duration of persistent anomalies (PAs), as well as the changes in PA behavior that are likely to occur as a result of warming due to greenhouse gas increases.
PAs are broader in spatial scale than the weather fronts and cyclones that are collectively referred to as synoptic systems. Studies of blocking show that synoptic systems play a large role in the onset and maintenance of blocks, a finding that holds true for PAs as well. The PIs hypothesize that the initiation and maintenance of PAs depends on smaller-scale processes that occur inside the synoptic systems, including the organization of rain-bearing clouds (where condensational heating occurs) into mesoscale features (rain bands and squall lines, for example). The hypothesis is motivated in part by studies showing that global weather and climate models with higher resolution do a better job in simulating blocks, despite the large size of blocks compared to grid spacing even in low resolution models. The PIs propose that higher resolution is better because it allows a more accurate representation of the much smaller mesoscale features where the condensational heating takes place. Better representation of condensational heating leads to more vigorous systems, which can more effectively move low vorticity air across the jet stream from the tropics to high latitudes as required for PA formation. One implication of this hypothesis is that models or climate states which are more conducive to high intensity synoptic systems will produce more strong PAs. This argument suggests that PAs could become stronger or more prominent as climate warms, as the greater moisture content of warmer air allows for more intense rainfall and condensational heating.
The project examines PAs in present-day climate by identifying a set of cases and performing "hindcast" simulations of those cases using a global atmospheric model (the Weather Research and Forecasting model, or the Model for Prediction Across Scales if it becomes available). Model configurations which produce the best simulations of these cases will be identified, and a number of diagnostics will be performed to identify the key ingredients which lead to PA initiation and persistence. Additional experiments are performed using a technique in which the initial atmospheric state for the simulation is modified to remove particular synoptic features, in order to assess the role of these features in PA formation. The impact of climate change on PAs is studied by repeating the hindcasts but with the background state modified to approximate the effects of greenhouse warming as simulated by climate models. Long model integrations are used to consider PA behavior in a statistical sense, and simple single-layer models are used to further examine the basic dynamics of PAs.
The behavior of PAs is a topic of practical as well as scientific interest, given the close association of PAs with high-impact weather events that affect human activities. The work addresses questions which are directly relevant to improving the ability of weather models to forecast PA-related extreme weather, and the ability of climate models to anticipate future changes in PA behavior. In addition, the project provides undergraduate research opportunities through two new courses emphasizing collaborative research, one on data analysis and the other on numerical simulations. An undergraduate internship is also supported in each summer of the project, and the position is advertised at minority-serving institutions. In addition, the project will employ and train two graduate students and a postdoctoral fellow, thereby providing future workforce development in this area of research. |
| 资源类型: | 项目
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| 标识符: | http://119.78.100.158/handle/2HF3EXSE/91246
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| Appears in Collections: | 全球变化的国际研究计划
科学计划与规划
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| Recommended Citation: | |
Walter Robinson. Extratropical Persistent Anomalies on a Warmer Earth: Connections to Extratropical Storms and Storm Tracks. 2016-01-01.
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