Dynamics of Interactions between Wave Packets and Explosive Cyclogenesis over Western North Pacific

西北太平洋波包与爆炸性气旋发生相互作用的动力学

• 批准号: 0757250
• 负责人: Edmund Chang
• 金额: $ 44.56万
• 依托单位: SUNY at Stony Brook
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-05-01 至 2013-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0757250&HistoricalAwards=false
• 关键词: Dynamics; Interactions; between; Wave; Packets

During the cool season, the western North Pacific is frequented by strong cyclones. Some of these deepen explosively to generate dangerous winds and huge waves. There are indications that these cyclones are less predictable than less intense storms. Western Pacific cyclones bring hazardous weather to the region; at the same time, they excite Rossby wave trains that propagate rapidly eastward to affect the U.S. and even Europe within a few days. Recent studies have shown that analysis and forecast errors over the western Pacific propagate quickly downstream to affect weather forecasts for the U.S. Recent statistical analyses by the investigator showed that cyclone development over the western and central Pacific is strongly affected by pre-existing upper-tropospheric wave packets over Asia - the frequency of occurrence of explosive cyclogenesis is significantly higher three days after wave packets having the appropriate configuration are found either over Russia or across southern Asia. Moreover, preliminary modeling studies suggest that explosive cyclogenesis that occurs under the influence of these wave packets may be much more predictable than that which occurs in the absence of wave packets - in some cases, western Pacific explosive cyclogenesis can be robustly forecasted up to eight days before it occurs. The main goal of this project is to explore and to understand the dynamics of the interactions between upper-level wave packets and surface cyclogenesis. In addition, factors affecting the predictability of these events will be explored, and the impacts of wave packets on U.S. weather will be examined. Cases in which cyclogenesis did not occur despite the presence of significant upstream dynamical forcings will be compared to cases in which cyclogenesis can be robustly simulated, in order to understand the conditions that inhibit or favor rapid cyclogenesis. A suite of modeling and diagnostic studies will be employed. The main modeling tool is the NCAR Community Atmospheric Model (CAM). For each selected case, ensemble data assimilation, using the technique of the ensemble Kalman filter, will be conducted using CAM. This ensemble of analyses will be used as initial conditions to obtain an ensemble of forecasts. With this forecast ensemble, the predictability of these events can be assessed. Ensemble-based sensitivity analyses will expose the important factors that affect the evolution of these events. The technique of potential vorticity diagnostics and inversion will be used to conduct feature-based sensitivity study to examine dynamical factors that may have significant impacts on the evolution of these events over the medium range. This study addresses a major issue for forecasting - explosive cyclogenesis generates high impact weather, and frequently these events are not well forecasted. The results may assist forecasters in interpreting model forecasts of these events by stratifying events into different types and quantifying the differences in predictability of each type. Detailed studies of the dynamics of these events will provide researchers with new information about how to improve the prediction of these events by clarifying the different roles played by diabatic processes, dynamics, and uncertainties in initial conditions. Western Pacific cyclones frequently excite Rossby wave trains that propagate eastward to produce high impact weather events, such as blizzards and floods, over the U.S. The broader impact of this study is in the significant societal benefits that can derive from improved forecasts of high impact weather.

在寒冷的季节，北太平洋西部经常有强气旋出没。其中一些会爆炸性地加深，产生危险的风和巨浪。有迹象表明，这些气旋比强度较小的风暴更难预测。西太平洋气旋给该地区带来危险的天气;同时，它们激发罗斯贝波列，迅速向东传播，在几天内影响美国甚至欧洲。最近的研究表明，西太平洋的分析和预报误差会迅速向下游传播，影响美国的天气预报。研究人员最近的统计分析表明，西太平洋和中太平洋的气旋发展受到亚洲上空先前存在的对流层上层波包的强烈影响。在俄罗斯或南亚上空发现具有适当结构的波包后三天，爆发性气旋生成的发生频率明显更高。此外，初步的模拟研究表明，在这些波包的影响下发生的爆发性气旋生成可能比没有波包的情况下发生的更可预测-在某些情况下，西太平洋爆发性气旋生成可以在发生前8天进行稳健的预测。这个项目的主要目标是探索和理解上层波包和地面气旋生成之间相互作用的动力学。此外，将探讨影响这些事件的可预测性的因素，并研究波包对美国天气的影响。尽管存在显着的上游动力强迫的情况下，气旋发生没有发生的情况下，气旋发生可以被鲁棒地模拟，以了解抑制或有利于快速气旋发生的条件进行比较。将采用一系列建模和诊断研究。主要的建模工具是NCAR社区大气模型（CAM）。对于每一选定的情况，将使用CAM进行使用集合卡尔曼滤波器技术的集合数据同化。这套分析将被用作初始条件，以获得一个整体的预测。有了这个预报集合，就可以评估这些事件的可预报性。基于总体的敏感性分析将揭示影响这些事件演变的重要因素。位涡诊断和反演技术将用于进行基于特征的敏感性研究，以检查可能对这些事件的中期演变产生重大影响的动力因素。这项研究解决了预报的一个主要问题-爆发性气旋生成产生高影响天气，而这些事件往往没有得到很好的预报。这些结果可以帮助预报员通过将事件分为不同类型并量化每种类型的可预测性差异来解释这些事件的模型预测。这些事件的动力学的详细研究将为研究人员提供有关如何通过澄清非绝热过程，动力学和初始条件的不确定性所发挥的不同作用来改善这些事件的预测的新信息。西太平洋气旋经常激发Rossby波列，向东传播，在美国产生高影响的天气事件，如暴风雪和洪水，这项研究的更广泛的影响是在显着的社会效益，可以从改善预测的高影响天气。