This is a post to document some details for the ERA-5 forced ACCESS-OM2 runs that I have completed to a state which I’m happy to share. I’m hoping others with an interest can jump in and do some analysis. Hopefully the runs will be useful to someone!
I’ve done 4 ERA-5 runs (RYF and IAF, 1-degree and 1/4-degree), with 4 equivalent JRA55-do forced runs for comparison, with details listed in the below table.
Initial analysis of some basic metrics can be found here for the IAF and here for the RYF. Please feel free to expand on these and share your findings here!
Thanks to @aekiss, @russfiedler, Nic Hannah, @Aidan and probably a bunch of other people I’ve missed for their contributions.
1 degree ACC Transport is a bit odd, where ERA5 takes off, then comes back down around 1980 and basically shadows the JRA55 value until they start to diverge a little from 2010
The relatively consistent drifts in global T is one thing that surprised me. Some of the adjustments in JRA55-do were made I think to reduce drift, and so I was expected larger drifts with ERA-5 without these adjustments. But the magnitude of the drift isn’t really any larger.
Likewise, the consistency between the circulation metrics is also remarkable. The resolution has a much bigger impact. I guess its saying that the bulk wind stresses between the two forcing products are consistent, and model physics is important.
I’m hoping @willrhobbs will do a more detailed analysis of sea ice. I’m not sure I know enough to offer any interpretations. However, it is interesting to see that 025deg_era5_iaf run does capture some of this year’s very low Antarctic sea ice, although it may not be as extreme as in observations.
One last thing: The original reason I was interested in these simulations was to see if they improved on JRA-55’s really weak tropical instability wave activity in the equatorial Pacific. There are suggestions from some papers that the very weak North Equatorial Counter Current in OMIP-2 forced simulations is because of some of the adjustments made to integrate scatterometry data in JRA55-do (but not in ERA-5). However, in the RYF 1/4-degree simulations TIWs are only slightly stronger in ERA-5, and still way too weak (see last plots in https://github.com/rmholmes/cosima-scripts/blob/master/ERA-5/ERA-5_Initial_Analysis-RYF-old_more_vars_equatorial.ipynb). I need to revisit this in the IAF simulations.
@Aidan I’m bringing a poster on (Antarctic) sea ice comparison to the COSIMA workshop between ERA5, the IAF and obs (1/4 degree model). Not sure how far I’ll get with it, but ideally I’ll get as far as the dynamic/thermodynamic tendency terms,.
For anyone who is using recent data from the access-om2-025/025deg_era5_iaf run, please note that I have just extended this run to the end of 2023. Note that 2023 is now output043 and run as one contiguous year, replacing the previous output043-045 which were irregular runs of just a few months.
I have also extended the access-om2-025/025deg_jra55_iaf_era5comparison run to the end of 2023 (this is the run that is an apples-to-apples comparison to 025deg_era5_iaf).
@micael can you please trigger an update of the cookbook database to take into account these changes?
Aidan
(Aidan Heerdegen, ACCESS-NRI Release Team Lead)
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Hi @willrhobbs. If this poster isn’t on the hive anywhere feel free to upload a PDR or PNG of the poster in this topic. Or in a separate topic and link to it.
@Aidan Here it is - the timeplot of sea ice anomalies is probably most relevant, although the maps show that the model had too much ice almost everywhere last winter
