Sub-Daily Scale Extreme Precipitation in Future Climate-Change Scenarios: A Pilot Study

次日极端降雨事件及其相关的对流降水系统将通过采用分层、跨尺度建模方法在北美明确模拟，最终在3D云解析模型模拟中达到高潮。实验设计包括全球气候模式（GCM）、嵌套区域气候模式（RCM）和子嵌套云分辨模式（CRM）集成。pi将采用两种基本方法：GCM-CRM嵌套和GCM-RCM-CRM嵌套。这是第一次尝试使用这两种方法来模拟美国本土历史上的强对流天气事件。个案研究事件将包括1974年4月3日的超级龙卷风爆发、1995年5月5日的暴洪和冰雹事件以及其他必要的事件。大部分工作“包括对事件的分析和验证，以及它们在统计工具开发中的应用”将致力于这些回顾性实验。然而，一旦确定了最佳方法，这些pi将在IPCC SRES排放情景的强迫下进行初步实验，以检验该方法模拟次日极端降雨事件对增强的温室强迫的响应的能力。主要目标是：1。通过使用一系列配置模拟历史事件，并将各种模拟与仪器数据进行比较，确定GCM、嵌套RCM和子嵌套CRM的单向耦合的最佳方法。2. 通过将模拟的未来事件与类似的历史事件进行比较，对未来排放情景下亚日极端降雨事件的特征、频率和地理分布进行初步预测。3. 通过将未来事件与特定类型的降水天气系统联系起来，从而与最可能伴随的危险现象联系起来，初步预测次日极端降雨将在何时何地伴随其他危险天气现象，如龙卷风和冰雹。该项目更广泛的影响包括教育和培训两名研究生。如果这个试点项目取得成功，它将展示在人类活动造成的气候中预测恶劣天气事件统计数据的潜力。这种预测所得的资料可能对决策者大有裨益。

Sub-daily extreme rainfall events and their associated convective precipitating systems will be explicitly simulated over North America by employing a hierarchical, scale-spanning modeling approach that culminates in 3D cloud resolving model simulations. The experimental design consists of global climate model (GCM), nested regional climate model (RCM), and sub-nested cloud-resolving model (CRM) integrations. The PIs will employ two basic approaches: GCM-CRM nesting and GCM-RCM-CRM nesting. This is the first attempt to simulate historical severe convective weather events over the contiguous United States using these two approaches. The case study events will include the tornado super-outbreak of 3 April 1974, the flash flood and hailstorm event of 5 May 1995, and others as deemed necessary. The majority of the work "to include the analysis and verification of the events, as well as their use in the development of the statistical tools" will be devoted to these retrospective experiments. However, once the optimum method for has been established, the PIs will perform an initial experiment forced by an IPCC SRES emissions scenario to examine the ability of that method to simulate the response of sub-daily extreme rainfall events to enhanced greenhouse forcing. The primary objectives are: 1. To identify the optimum methodology for one-way coupling of a GCM, a nested RCM and a sub-nested CRM by simulating historical events using a range of configurations and comparing the various simulations against instrumental data. 2. To yield an initial projection of the characteristics, frequency, and geographical distribution of sub-daily extreme rainfall events for a future emissions scenario, by comparing the simulated future events to similar historical events. 3. To yield an initial projection of where and when the sub-daily extreme rainfall will be accompanied by other hazardous weather phenomena such as tornadoes and hail, by associating the future events with specific types of precipitating weather systems and hence with the most likely attendant hazardous phenomena. The broader impacts of the project include the education and training of two graduate students. If this pilot project is successful, it will demonstrate the potential for projecting statistics of severe weather events in a climate forced by human activities. Information from such projections could be of significant benefit to policy makers.