Interaction between Low-Frequency Waves and High Frequency Eddies

低频波与高频涡流之间的相互作用

• 批准号: 9103647
• 负责人: Huug van den Dool
• 金额: $ 21.55万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1991
• 资助国家: 美国
• 起止时间: 1991-07-01 至 1994-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9103647&HistoricalAwards=false
• 关键词: Interaction; between; Low; Frequency; Waves

The time-averaged (climatological) extra-tropical atmospheric flow shows a definite spatial arrangement of areas of locally maximum variance ("storm tracks") located east of equatorward extending meanders (pressure trough) in the climatological jet-stream. Van den Dool and Cai propose to study the temporal variations of the flow which underlie this climatic feature. They posit a complementary inter-relationship between slowly-varying ("low frequency") planetary-scale waves and rapidly changing ("high-frequency") synoptic scale eddies. This would suggest that there exist traveling storm track regions downstream of traveling low-frequency waves, which are obscured in the time average. In fact, they report on a pilot study which demonstrates the existence of such regions in the mid- troposphere. They used a novel analysis technique, which records high-frequency activity in a frame which follows an identifiable feature of the low-frequency flow as it travels about the mid- latitudes. Having demonstrated the existence of traveling storm tracks, they now propose extended analyses to elucidate the three-dimensional structures of both the low-frequency and high- frequency features as seen in this moving ("phase-transformed") frame, and the symbiotic relationship between them. The results of the proposed study will form the basis of future attempts to extend detailed day-to-day weather forecasts out to ranges that exceed a week.

时间平均（气候学）热带大气流显示了位于气候急流中向赤道延伸的曲流（压力槽）以东的局部最大方差区域（“风暴轨迹”）的明确空间排列。 范登杜尔和蔡提议研究这种气候特征背后的气流的时间变化。 他们假设缓慢变化（“低频”）行星尺度波和快速变化（“高频”）天气尺度涡流之间存在互补的相互关系。 这表明在行进的低频波下游存在行进的风暴路径区域，这些区域在时间平均值中被掩盖。 事实上，他们报告了一项试点研究，该研究证明了对流层中层存在此类区域。 他们使用了一种新颖的分析技术，该技术将高频活动记录在一个框架中，该框架遵循低频流在中纬度地区传播时的可识别特征。 在证明了移动风暴路径的存在之后，他们现在提出了扩展分析，以阐明在这个移动（“相变”）框架中看到的低频和高频特征的三维结构，以及它们之间的共生关系。 拟议研究的结果将构成未来尝试将详细的每日天气预报扩展到超过一周的范围的基础。