The representation of the winter and summer extratropical storm tracks in
both hemispheres is evaluated in detail for the available models in the 6th
phase of the Coupled Model intercomparison Project (CMIP6). The state of
the storm tracks from 1979-2014 is compared to that in ERA5 using a Lagrangian objective cyclone tracking ...
The representation of the winter and summer extratropical storm tracks in
both hemispheres is evaluated in detail for the available models in the 6th
phase of the Coupled Model intercomparison Project (CMIP6). The state of
the storm tracks from 1979-2014 is compared to that in ERA5 using a Lagrangian objective cyclone tracking algorithm. It is found that the main biases
present in the previous generation of models (CMIP5) still persist, albeit to a
lesser extent. The equatorward bias around the SH is much reduced and there
appears to be some improvement in mean biases with the higher resolution
models, such as the zonal tilt of the North Atlantic storm track. Low resolution models have a tendency to under-estimate the frequency of high intensity
cyclones with all models simulating a peak intensity that is too low for cyclones in the SH. Explosively developing cyclones are under-estimated across
all ocean basins and in both hemispheres. In particular the models struggle
to capture the rapid deepening required for these cyclones. For all measures,
the CMIP6 models exhibit an overall improvement compared to the previous
generation of CMIP5 models. In the NH most improvements can be attributed
to increased horizontal resolution, whereas in the SH the impact of resolution
is less apparent and any improvements are likely a result of improved model
physics.