Very high-resolution downscaling of the NZESM
Simulating New Zealand’s climate at fine spatial scales
Heavy rainfall and extreme winds affect communities and economic activities in New Zealand. Potential changes in these and other weather processes may be better understood by simulating them at very high spatial resolution.
The aim of this project is to develop a climate model for New Zealand at a very high spatial resolution of around 1 to 2.5 km. At this resolution, the steep, complex terrain of New Zealand is well resolved.
This improves the simulation of rainfall over mountain catchments, which is critical to national water resources. The model can also explicitly represent some small-scale vertical air movements, called convection, which influence the development of clouds and heavy rainfall events. This model is therefore termed a convection-permitting model (CPM). The CPM will be linked to the New Zealand Earth System Model (NZESM), via an intermediate regional climate model (RCM) running at a spatial resolution of 12 km.
Simulating climate at this fine spatial scale requires huge computational resources, particularly if the model spans the whole of New Zealand, and this capability will take some years to develop. The CPM will therefore be experimental to begin with: simulations will be restricted to short time-slices and, if necessary, geographic sub-regions of the country.
It’s important to start building this capability now, so that we can in time learn more about what changes are likely to occur in New Zealand climate later this century.