Computer Cluster for Numerical Modelling and Simulation

气候地理工作组的重点是在区域和全球范围内对山地冰川进行数值模拟，以重建过去的冰川动态，进行预测和冰川-气候相互作用的概念研究。研究结果将用于调查冰川对季节性水供应的贡献，并量化冰川对区域海平面变化的贡献。我们还调查了冰川变化的这些影响的社会后果。我们的工作基于开放全球冰川模型（OGGM，http://oggm.org），该模型是由该小组开发的，国际社会的贡献越来越大。我们进一步应用大气的统计和动力学降尺度来研究冰-气边界的相互作用，这是由山区复杂的地形所决定的。由于OGGM模拟的冰川不是动态耦合的，因此模型的全局运行由大量独立的过程组成，从而导致模型具有很好的可扩展性。因此，原则上，OGGM非常适合部署在HLRN等区域/国家高性能计算中心。在实践中，OGGM依赖于大量的外部数据源，这些数据源经常更新并从互联网动态加载，这使得这是不可能的。出于安全考虑，这在HLRN是不可能的。或者，数据可以打包和上传，这是不切实际的，因为所需的数据量（约。1 TB/全局模型运行）。 此外，由于OGGM处于非常活跃的开发中，它需要最新的Python环境和频繁的更新。这种需求与计算中心（如HLRN）对稳定性的需求不兼容，这会阻止用户直接控制已安装的软件包。测试表明，OGGM对最新软件包的依赖阻止了它在HLRN资源上的部署。由于模型开发是正在进行的工作的一个重要方面，因此需要能够灵活分配和配置的本地资源。 最后，除了（可扩展性好）的任务建模大量的个别冰川，有一些“全球”的任务（主要是关于模型验证和优化），不能并行化，因此需要高的最大挂钟时间。这里请求的计算集群需要确保工作组所需的计算资源。

The working group Climate Geography focusses on numerical modeling of mountain glaciers on the regional and global scale, both for reconstructing past glacier dynamics, for producing projections and for conceptual studies of glacier-climate-interactions. The results are used for investigating the contribution of glaciers to seasonal water availability and for quantifying the contribution of glaciers to regional sea-level change. We also investigate societal consequences of these impacts of glacier change. Our work is based on the Open Global Glacier Model (OGGM, http://oggm.org), which is developed by the group with growing contributions from the international community. We further apply statistical and dynamical downscaling of the atmosphere to investigate interactions at the ice-air boundary, which are governed by the complex topography of mountain regions. Since the glaciers simulated by OGGM are not dynamically coupled, a global run of the model consists of a great number of independent processes, leading to very good scalability of the model. In principle, OGGM is therefore well suited to be deployed at regional/national high performance computation centers like HLRN. In practice, this is made impossible by the dependency of OGGM on a great number of external data sources, which are updated frequently and dynamically loaded from the internet. This is impossible at HLRN because of security considerations. Alternatively, data could be packaged and uploaded, which is impracticable because of the required amount of data (ca. 1 TB per global model run). Moreover, since OGGM is in very active development, it needs an up-to-date Python environment and frequent updates. This demand is incompatible with the compute centers’ (like HLRN) need for stability, which prevents users from getting direct control of the installed packages. Tests have shown that the dependence of OGGM on up-to-date software packages prevents its deployments at HLRN resources. Since model development is an important aspect of the ongoing work, local resources that can allocated and configured flexibly are needed. Finally, apart from the (well scalable) tasks of modeling a great number of individual glaciers, there are certain “global” tasks (mostly concerning model validation and optimization) that cannot be parallelized and thus need high maximum wall clock times. The compute cluster requested here is needed to secure the computational resources needed by the working group.