The New Zealand Earth System Model (NZESM)

The NZESM as an infographic

This page gives you an overview of the NZ earth system modelling project, including updates on current and planned model simulations.

The basic make-up of the model 

The New Zealand Earth System Model (NZESM) is a state-of-the-art modelling system that couples together representations of atmospheric physics (wind, temperature and water in the atmosphere and the processes that link them), ocean dynamics (oceanic temperatures, currents and salinity), sea ice (both sea ice coverage and sea ice thickness), and land physics (soil moisture, soil temperature and river run-off).  

In addition, the model represents some chemical, biological and land-ice aspects of the “earth system”: chemistry of the lower and middle atmosphere (with a focus on ozone), ocean “biogeochemistry” (think plankton and dissolved carbon), and Antarctic ice shelves. 

Relationship between the NZESM and the UK Earth System Model 

In New Zealand, we don't have the resources to develop or even to maintain our own, fully independent earth system model.  

We therefore develop the NZESM in partnership with the Unified Model Consortium, led by the UK Met Office. The NZESM is derived from and feeds back into the UK Earth System Model (UKESM). 

Further, all the components that feed into the NZESM represent large, multi-institutional model development efforts.  

The Deep South Challenge model development effort is geared towards advancing the model in several areas that are of key interest to New Zealand. Check out the range of projects we have in our earth system modelling and prediction programme here.

Producing useful climate simulations using a hierarchy of models

A global climate or earth system model is generally characterised by relatively low resolution, such as 1 to 2 degrees in latitude and longitude in the atmosphere (around 100 to 200 kilometres). This means a country like New Zealand is covered by a small number of grid points, which in turn means that the effects of local geography (for example, the Southern Alps), are not fully represented in these simulations.  

A global model is generally used to assess large-scale features of climate change, such as the global-mean surface temperature. To assess local-scale questions (at around 10 to 15 kilometres), global climate model simulations need to be followed by regional climate modelling. In New Zealand, it looks something like this:

The hierarchy of models used to produce climate projections for New Zealand. There are a few other models in use not shown, e.g. WaveWatch (to model wave height), [email protected] ANZ (to produce large ensembles) and HadGEM3 (the simpler physics-only climate model).

Current and planned simulations for the Deep South National Science Challenge

The UKESM will contribute to the upcoming 6th Coupled Model Intercomparison Project (CMIP6), which will inform the Sixth Assessment Report of the IPCC.  

The NZESM will exercise some liberty when configuring the model for our own planned production simulations, in ways that may differ from UKESM.  

We also will produce some simulations using the HadGEM3 climate model, which is the physical basis of UKESM, but which lacks atmospheric chemistry, biogeochemistry and ice shelves. We will be running some atmosphere-only and ocean-only simulations. 

Have a look at this Gantt chart of our planned simulations with different model constellations:

How does our earth system modelling programme assist our other programmes conducting research into climate adaptation in New Zealand?

One of the unique aspects of the Deep South Challenge is the way we join together physical science, modelling, social science and political response.

By building strong relationships between our modelling, Vision Matauranga and Impacts & Implications programmes, we're helping communities, councils, property owners and businesses access reliable climate information in formats they can understand and apply:

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