MRI: Acquisition of a Computing Cluster for Atmospheric and Geophysical Research

这是一项重大研究仪器(MRI)奖，用于资助购买一台5节点集群计算机，以支持大气和海洋科学的研究和教育活动。在大气方面，该机器的主要应用是扩展的全大气社区气候模式(WACCM-X)，该模式用于研究平流层突然变暖事件(SSW)影响电离层的机制。SSW是冬季平流层绕极环流的大规模扰动(通常在北极上空)，其中平流层温度在几天内可上升高达50摄氏度。虽然这些扰动发生在北极上空和大约20公里的高度，但它们可以影响300公里高度赤道上空电离层的电子含量，在那里它们可以干扰用于导航、通信和其他目的的卫星。这种影响在如此远的距离内传播的机制尚不清楚，但据信涉及大气潮汐的垂直传播。这里的工作验证了SSW影响可能发生的想法，因为SSW激发的西风传播的行星尺度波产生了影响潮汐垂直传播的纬向风异常，以及另一种假设，即机制涉及臭氧吸收紫外线导致的加热变化。海洋工作考虑了沿海海洋中的波浪-湍流相互作用，这是理解与侵蚀和污染相关的沉积物输送和理解海洋生物必不可少的水性质的重要问题。这项工作使用了大涡模拟(LES)模型--频谱多域模型，来模拟近岸海洋(海底深度高达100米左右)中的波浪。理解波动和湍流相互作用的一个关键问题是将运动场分为波动轨道运动和湍流，PI使用适当的正交分解(POD)进行攻击，其中各个模式表示流动中不同的长度尺度，并且具有遵循经典Kolmogorov级联的能级。集群计算机被用来计算三维POD，它提供了不同的模式集来表示在中等空间尺度上发生的波轨道运动、小尺度湍流以及两者之间的非线性相互作用。MRI奖通过为研究和教育提供基础设施而产生更广泛的影响，包括海洋、大气和计算机科学课程。特别是，计算机支持新成立的海岸和海洋系统科学博士项目，这是该大学的第一个博士项目。此外，本科生强烈参与集群计算机的组装和维护，从而获得使用硬件集成和操作系统的动手技能。

This is a Major Research Instrumentation (MRI) award which funds the acquisition of a 5-node cluster computer to support research and education activities in atmospheric and oceanic sciences. On the atmospheric side the primary application of the machine is the Extended Whole Atmosphere Community Climate Model (WACCM-X), which is used here to study the mechanisms through which sudden stratospheric warming events (SSWs) affect the ionosphere. SSWs are large-scale disturbances of the stratospheric circumpolar circulation in winter (typically over the North Pole) in which stratospheric temperature can rise by up to 50C over the course of a few days. While these disturbances occur over the pole and at altitudes of about 20km, they can affect the electron content of the ionosphere over the equator at an altitude of 300km, where they can interfere with satellites used for navigation, communication, and other purposes. The mechanisms by which this influence propagates over such great distances is not known but is believed to involve the vertical propagation of atmospheric tides. Work here tests the idea that the SSW impact can occur because westerly propagating planetary-scale waves excited by the SSW produce zonal wind anomalies which affect the vertical propagation of tides, and the alternative hypothesis that the mechanism involves changes in the heating due to ultraviolet absorption by ozone.The oceanographic work considers wave-turbulence interactions in the coastal ocean, an important issue for understanding the transport of sediments associated with erosion and pollution and for understanding water properties essential to ocean biology. The work uses a large eddy simulation (LES) model, the Spectral Multi-domain model, to simulate waves in the near-shore ocean (bottom depths up to 100m or so). A key issue in understanding the interaction of waves and turbulence is the problem of separating the motion field into wave orbital motions and turbulence, which the PIs are attacking using a proper orthogonal decomposition (POD) in which individual modes represent different length scales within the flow and have energy levels which follow the classical Kolmogorov cascade. The cluster computer is used to calculate a three-dimensional POD which provides separate sets of modes to represent the wave orbital motions, small-scale turbulence, and nonlinear interactions between the two occurring at intermediate spatial scales.The MRI award has broader impacts by providing infrastructure for research and education, including courses in oceanic, atmospheric, and computer science. In particular, the computer supports the newly formed PhD program in Coastal and Marine System Science, the first doctoral program at the university. Also, undergraduate students are strongly engaged in the assembly and maintenance of the cluster computer, thus acquiring hands-on skills in working with hardware integration and operating systems.