The Response of Convective Precipitating Storms to Anthropogenically Enhanced Global Radiative Forcing

对流性降水风暴（CPS）和冰雹、破坏性地面风、龙卷风和山洪等相关危害对生命和财产构成严重威胁。 这些危险现象是由大气湿度、温度和风的三维分布决定的。 简单的物理参数表明，这些状态变量的变化所造成的人为增加温室气体（GHG）浓度将反过来影响CPS的频率和强度。 在早期的工作中，首席研究员（PI）已经表明，有价值的洞察力，这种本地响应的动态可以获得使用气候模式，对流过程参数化在次网格尺度。 然而，这种“间接”方法的局限性突出了应用数值模式的重要性，明确解决对流风暴在大的大陆地区。在初步工作中，PI还建立了伸缩模拟策略的基本可行性，该策略包括嵌套在全球模型（G-C策略）中的对流云允许模型[天气研究和预报（WRF）模型]和嵌套在全球模型中的区域模型（G-R-C策略）。 在这一试点工作取得成功的基础上，PI将利用这些战略来生成现代和未来时期的CPS气候学和相关危害。 将进行一些使用再分析作为全球驱动因素的初步实验，主要是为了揭示CPS统计中的模型偏差。 大部分实验将涉及WRF模型的高分辨率集成，由政府间气候变化专门委员会关于排放情景的特别报告强制的气候模型集合驱动。 这个合奏将有助于量化的CPS动态变化的大尺度边界条件的敏感性。伴随着这些实验将是新的技术来分析信息丰富的WRF模型输出。 首先，以前开发的自动化，面向对象的分析程序将用于识别，表征和分类的沉淀系统。 这将允许进一步考虑属性，如对流与层状降水的面积范围。第二，代理方法将适用于提供一个量化的本地规模的危险天气伴随着CPS。 例如，将使用经验参数中的风暴尺度风场来估计龙卷风的发生。 还将制定类似的破坏性风和冰雹参数。 最后，将采用称为子采样的强大的恢复技术来计算观测和建模的时间序列的统计特征及其置信区间，包括均值、方差、偏度、相关性和极值分布的参数。这一项目的智力价值是，它将提供对流降水风暴和相关现象对温室气体浓度增加所引起的全球辐射强迫增强的潜在反应的估计。 这将通过一种新的跨尺度建模方法，然后通过同样新颖的分析技术来实现。该项目的更广泛影响之一是，它将提供可用于评估人为气候变化潜在影响的额外信息。 该项目还将影响普渡大学的研究生和本科生教育。 例如，很大一部分研究将由研究生在教师的指导下进行，从而培养下一代气候和天气科学家的尖端技能。 为了提高这一技能，将为普渡大学的学生和教师提供气候建模工具的年度研讨会。 此外，方案研究所试点项目的组成部分已经纳入了从非专业、本科到研究生的课程，包括编制关于气候统计的研究生课程。PI将继续（并扩大）这种纳入研究生和本科课程。

Convective precipitating storms (CPSs) and the associated hazards of hail, destructive surface winds, tornadoes, and flash floods pose serious risks to life and property. These hazardous phenomena are governed by the three-dimensional distributions of atmospheric moisture, temperature, and wind. Simple physical arguments suggest that changes in these state variables resulting from anthropogenic increases in greenhouse gas (GHG) concentrations will in turn affect the frequency and intensity of CPSs. In earlier work, the Principal Investigators (PIs) have shown that valuable insight about the dynamics of this local response can be gained using climate models in which convective processes are parameterized at subgrid scales. However, the limitations of this "indirect" approach highlight the importance of applying numerical models that explicitly resolve convective storms over large continental areas. In preliminary work, the PIs also established the basic viability of telescoping modeling strategies that consist of integrations of a convective-cloud-permitting model [the Weather Research and Forecasting (WRF) model] nested within a global model (the G-C strategy) and within a regional model that is itself nested within a global model (the G-R-C strategy). Building on the success of this pilot work, the PIs will utilize these strategies for the purpose of generating climatologies of CPSs and associated hazards over modern and future time periods. Some initial experiments using reanalyses as the global driver will be conducted, primarily to reveal model biases in the CPS statistics. The bulk of the experimentation will involve high-resolution integrations of the WRF model, driven by an ensemble of climate models forced by Intergovenmental Panel on Climate Change Special Report on Emissions Scenarios. This ensemble will help to quantify the sensitivity of the CPS dynamics to variations in the large-scale boundary conditions. Accompanying these experiments will be novel techniques to analyze the information-rich WRF model output. First, previously developed automated, object-oriented analysis procedures will be used to identify, characterize, and classify the precipitating systems. This will allow further consideration of attributes such as the areal extent of convective versus stratiform precipitation. Second, a proxy method will be adapted to provide a quantification of local-scale hazardous weather attendant with the CPSs. For example, tornado occurrence will be estimated using the storm-scale wind field in an empirical parameter. Similar parameters for damaging wind and hail will also be developed. Finally, a powerful resampling technique known as subsampling will be employed to compute statistical characteristics and their confidence intervals from observed and modeled time series, including means, variances, skewnesses, correlations, and parameters of extreme value distributions. The intellectual merit of this project is that it will provide an estimate of the potential response of convective precipitating storms and associated phenomena to the enhanced global radiative forcing associated with increases in GHG concentrations. This will be achieved through a novel scale-spanning modeling approach, and then through equally novel analysis techniques. One of the broader impacts of this project is that it will offer additional information that can be used to assess the potential impacts of anthropogenic climate change. The project will also affect graduate and undergraduate education at Purdue University. For example, a significant portion of the research will be performed by graduate students under the mentorship of faculty, thereby training the next generation of climate and weather scientists in cutting edge skills. To enhance this skill set, an annual workshop on climate modeling tools will be offered to Purdue students and faculty. In addition, components of the PIs' pilot project have already been incorporated into courses from the non-major, undergraduate level to the graduate level, including development of a graduate course on climate statistics. The PIs will continue (and expand) this incorporation into the graduate and undergraduate curriculum.