Understanding Tornadoes and Their Parent Supercells Through Ultra-High Resolution Simulation/Analysis

这一提议是为了在2011年投入使用的Blue Waters计算机系统上临时分配时间，以及为支持Blue Waters项目团队和供应商技术团队的各种合作者进行技术协调提供旅费。该项目包括对支持龙卷风发展和寿命的条件的研究。该方法是利用一个复杂的大气动力学和热力学模型，对超级单体和演变中的龙卷风之间的相互作用进行数值模拟。这些模拟将解决影响龙卷风演变的小尺度、动态活动特征，包括龙卷风的浅层流入和形成的薄降水带。所使用的数值模式将是一个名为CM1的平行风暴尺度大气模式的发展。这项工作将使人们更好地了解超级单体内部和周围不同的环境条件对龙卷风的发生和动力学的影响。需要“蓝水”这样规模的资源的理由是，如果没有它，就不可能解决几十米厚的薄降水幕（可能将大量角动量从云底转移到地面）、龙卷风流入层（也有几十米厚）和低洼冷空气池的影响。要诊断和理解龙卷风形成期间和之后超级单体内部的微物理、浮力和涡度动力学之间的相互作用，需要比现有计算系统更高的分辨率。从该项目中获得的见解应该有助于提高龙卷风预报能力，从而有可能通过早期和更准确的预警来提高安全性。更一般地说，本研究产生的数据可用于改进天气尺度模式的子网格参数化，提高其预测恶劣天气的能力。

This proposal is for a provisional allocation of time on the Blue Waters computer system, due to become operational in 2011, and for travel funds to support technical coordination by various collaborators with the Blue Waters project team and vendor technical team.The project involves a study of the conditions that support tornado development and longevity. The approach is to simulate numerically the interaction between a supercell and an evolving tornado using a sophisticated model of atmospheric dynamics and thermodynamics. These simulations will resolve small-scale, dynamically active features that influence the evolution of the tornado, including the shallow inflow into the tornado and the thin bands of precipitation that form. The numerical model used will be a development of a parallel, storm-scale, atmospheric model named CM1. The work will produce a better understanding of the influence of different environmental conditions within and around the supercell on the genesis and dynamics of tornadoes. The rationale for requiring a resource of the scale of Blue Waters is that, without it, it will not be possible to resolve thin curtains of precipitation, tens of meters thick, which potentially transfer large amounts of angular momentum from cloud-base to ground, the tornado inflow layer, also tens of meters thick, and the influence of low-lying pools of cold air. Being able to diagnose and understand the interplay between microphysics, buoyancy and vorticity dynamics within the supercell, during and after tornado-genesis, requires higher resolution than is possible on existing computing systems.The insights gained from this project should be helpful in improving tornado forecasting capability which has the potential to increase safety through early and more accurate warnings. More general, data generated by this study may be used to improve sub-grid parameterizations for synoptic scale models, improving their ability to forecast severe weather.