Analysis of Predictability of Convective Initiation and Morphological Evolution Using Near-Cloud Permitting Grid Spacing Models

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。对中尺度对流系统（mcs）的形成和形态演变进行精确的计算机数值模拟对于定量降水和恶劣天气风险的预报都很重要。mcs体现了雷暴线和/或集群以及伴随的较轻降水，这些降水占美国中西部生长期降雨的大部分。计算速度的提高使得操作模型网格间距能够扩展到能够解决这些风暴系统中单个云特征的尺度。即便如此，这些云的形成发生在如此小的空间尺度上（而且充分依赖于这些精细尺度上测量不完美的初始大气条件），以至于无法在这些模型中得到适当的表示。由于类似的原因，较大的成熟雷暴要素的强度和水平模式的后续模式演变可能不准确地描绘出来，并进一步受到云微物理方案的缺陷的影响，这些方案反过来影响模拟的冷池/阵风锋以及由此产生的低层云强迫。本研究将利用大量观测和模拟MCS事件的档案，包括来自IHOP和BAMEX现场实验以及NOAA危险天气试验台项目的观测，以实现三个主要目标：(1)完成对存档模拟和对流起始和MCS演变的相应观测的详细分析，以确定控制这些属性的关键过程；(2)进行系统测试，以确定这种模拟对云微物理过程的表示和适合最先进大气模型的细网格尺度特征的新参数化方法的敏感性；(3)利用基于实体的验证技术和数值模拟集合，开发改进QPF（定量降水预报）指导的方法。这项研究的智力价值在于实现对数值模拟依赖于模型分辨率和所采用的特定参数化方案之间复杂关系的更全面和更准确的理解，这些方案在某些情况下可以追溯到十多年前开发的更粗糙的模型。通过支持一些研究生的教育，通过在课堂和学生项目导向的本科学习中纳入新兴研究主题，通过与国家气象局预报员和公共媒体采访的互动，以及通过改进定量降水数量/时间和影响公众的恶劣天气的预测方法，将产生更广泛的影响。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Accurate computer-based numerical simulations of the initiation and morphological evolution of mesoscale convective systems (MCSs), which embody lines and/or clusters of thunderstorms and attendant lighter precipitation accounting for the bulk of growing-season rainfall over the midwestern U.S., are important for forecasts of both quantitative precipitation amounts and severe weather risks. Increased computational speed has allowed operational model grid-mesh spacing to extend to scales capable of resolving individual cloud features within these storm systems. Even so, the initiation of these clouds occurs on spatial scales so small (and is moreover sufficiently dependant on imperfectly-measured initial atmospheric conditions at these fine scales) as to defy proper representation in these models. Subsequent modeled evolution of the intensity and horizontal patterning of larger mature thunderstorm elements may be inaccurately portrayed for similar reasons, and is further impacted by deficiencies in cloud microphysical schemes that in-turn influence simulated cold pools/gust fronts and resultant low-level cloud forcing.This study will exploit an extensive archive of observed and simulated MCS events, including observations from the IHOP and BAMEX field experiments and NOAA Hazardous Weather Testbed project, to accomplish three primary objectives: (1) Complete detailed analyses of archived simulations and corresponding observations of convective initiation and MCS evolution to identify key processes controlling these attributes; (2) perform systematic tests to determine sensitivity of such simulations to both representations of cloud microphysical processes and novel parameterization methods appropriate to fine-mesh scales characteristic of state-of-the-art atmospheric models; and (3) develop methods for improved QPF (Quantitative Precipitation Forecast) guidance making use of entity-based verification techniques and ensembles of numerical simulations. The intellectual merit of this research rests in achieving a fuller and more accurate understanding of numerical simulation dependencies on complex relationships between model resolution and those specific parameterization schemes being employed, which in some cases trace back to far-coarser models developed a decade or more ago. Broader impacts will emerge through support of the education of several graduate students, through inclusion of emerging research themes in classroom and student project-oriented undergraduate studies, via interactions with National Weather Service forecasters and public media interviews, and through contributions to improved methodologies for forecasts of quantitative precipitation amounts/timing and severe weather impacting the public.