Sea ice dataset of UM regional model driven by ERA5

Atmosphere Regional Nesting Suite
1

Hi Team,

When I use ERA5 to drive the UM regional model as initial and lateral boundary conditions, I note that ERA5 also provides information of sea ice cover. In the regional ancillary suite (copied from u-bu503), I found the sea surface temperature and sea ice concentration come from monthly climatology of HadISST dataset https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2002jd002670.

Does anyone know which sea ice dataset is used when driving the UM regional model with ERA5, HadISST or ERA5?

Thanks very much!

Zhangcheng

2

Hi Zhangcheng,

The short answer is the sea-ice concentration is coming from ERA5 via the Fields File reconfiguration of the ERA5 data via the GRIB file format.

Please be aware though that sea surface temperature is NOT coming from ERA5 via the same mechanism as it is not included as a GRIB variable.

Also be aware that there were issues with sea-ice concentration values if using ERA5 and ERA5-land with the older nci_era5grib command.

@dale.roberts, has the the sea-ice concentration error been fixed in the new nci_era5grib command?

2 Likes
3

Also please note, I noticed that the SEA-ICE TEMPERATURE field is not being set properly via the reconfiguration. This is not an issue for the regions we have been running because there is no sea ice.

Please let me know if you need help and we can look into it.

5

Lastly, it depends regional modelling setup you are using.

If you using the AUS2200 setup, the sea-ice may be being restored back to the ancillary to account for the nci_era5grib issue.

Again, please reach out if you need help and I will try to direct you.

1 Like
6

Hi @cbengel

Yes, I can confirm the anomalous sea ice issue is resolved in the latest version of era5grib, however, that version isn’t yet available in analysis3-unstable yet, its still undergoing testing. It can be pip install’d into a virtual environment though.

1 Like
7

Thanks @cbengel! It’s really good to know that :slight_smile:.

Sorry for responding late as I just came back from leave.

Many thanks,
Zhangcheng