Geophysical flow dynamics using pulsed Doppler radar

大规模移动流是世界各地的重大自然灾害，但我们预测其行为和规划其影响的能力有限，部分原因是我们缺乏对其流动动力学的了解。本研究将通过在雪崩和火山试验场进行精心控制的试验，研究地球物理质量运动流动过程的动力学（特别是雪崩和火山碎屑流）。这项研究将利用一种先进的新型多普勒雷达成像仪器，能够形成各种地球物理事件的二维动画图像。在英国皇家学会的支持下，伦敦大学学院正在开发这种雷达，它可以穿透雪崩和火山碎屑流周围的悬浮物，对流的密集部分（通常是风险分析中最重要的部分）进行成像。先进的信号处理算法将用于生成流的结构和动力学的详细模型。目前，光电仪器可以在单点提供这样的信息，现有的多普勒雷达可以提供流速的粗略图像，但平均超过50米，只能给出流速大小的总体测量（没有方向信息）。我们的仪器将把平均距离缩短到1米，这样，就可以第一次获得流动中单个块的信息，并根据它们对整体流动动力学的重要性进行评估。因此，我们可以评估为描述这些过程而提出的各种流动规律的有效性。这将通过将模型中的系数值限制在合理的值并直接拒绝某些提出的流动规律来改进这些流动过程的模型。这将导致这些过程的更准确的建模，这反过来将改进风险分析和防御结构的设计。因此，这项研究将大大增加我们对流动运动的理解，并将英国在这一领域的研究地位提高到国际领先水平。

Mass movement flows are a significant natural hazard throughout the world and yet our ability to predict their behaviour and plan for their effects is limited, in part, by our lack of understanding of their flow dynamics. This research will investigate the dynamics of geophysical mass movement flow processes (specifically snow avalanches and pyroclastic flows) by means of carefully-controlled trials at avalanche and volcano test sites. This research will utilise a sophisticated and new Doppler radar imaging instrument, able to form two-dimensional animated images of a variety of geophysical events. This radar has been under development at University College London, supported by the Royal Society, and permits imaging of the dense parts of the flow (often the most important component for risk analyses) by penetrating the suspended matter surrounding snow avalanches and pyroclastic flows. Advanced signal processing algorithms will be used to generate detailed models of the structure and dynamics of the flow. At present, opto-electronic instruments can provide such information at a single point and existing Doppler radar can provide crude images of the flow speed, but averaged over 50 m and only giving an overall measure of the velocity magnitude (with no information on direction). Our instrument will reduce the averaging distance to just 1 m so that, for the first time, information on individual blocks in the flow can be obtained and assessed in relation to their significance for the overall flow dynamics. Thus, we can assess the validity of a variety of flow laws that have been proposed for describing such processes. This will lead to improved models for these flow processes by limiting the values of coefficient in the models to reasonable values and rejecting some proposed flow laws outright. This will lead to more accurate modelling of these processes, which in turn will improve risk analyses and the design of defensive structures. This study will therefore considerably increase our understanding of flow movement and raise the status of UK research in this area to internationally-leading standards.