[A-CG45] Water and sediment dynamics from land to coastal zones

[ACG45-P02] What's the value of super-high-resolution global river simulation?

*Dai Yamazaki¹, Misako Hatono², Tomoko Nitta¹ (1.Institute of Industrial Sciences, The University of Tokyo, 2.Hiroshima University)

Keywords:Global River Model, Super-high-resolution, Digital Earths

Global river dynamics models are widely used as a river sub-model in Earth System Models and as a tool for large-scale flood risk assessment. In recent years, in the field of earth system modeling, attempts have been made to represent physical processes related to global environment prediction in super-high resolution (km scale), such as WCRP's Light House Activity “Digital Earths” and European Commission's “Destiny Earth” project. In response to this trend, the global river hydrodynamic model CaMa-Flood is updated for simulations at a global 1 arcmin resolution (about 1 km) by hybrid parallelization using MPI and OpenMP. However, although super-high-resolution simulation is useful for benchmarking model capability and detecting and improving bottlenecks, it has the problem of requiring extremely high computational costs. It is desirable to carry out complex earth system modeling considering the carbon cycle and flood risk assessment using large-scale climate ensemble data at medium to high resolution (about 20-5 km). Since CaMa-Flood treats flood inundation as sub-grid physics, it may be possible to obtain the same results as super-high-resolution simulations at medium to high resolutions. Therefore, in this study, the merits of ultra-high resolution are clarified by comparing the results of the realized ultra-high resolution (global 1 arcmin) river water dynamics simulation with the results of medium to high resolution simulation (global 15 to 3 arcmin). At the same time, we will discuss how acceptable medium-resolution to high-resolution simulations are.