Support ERA5 forcing #242
Comments
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Note that JRA55-do has velocity components, temperature and humidity all at 10m height. |
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Re. using ERA5 for initial conditions: SST and SIC are available in ERA5. |
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(in response to @nichannah's email)
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re. above, from TWG 21 July 2021:
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Quick update. A new experiment has been created with update config/input files including remapping weights. I've still got some work to do to modify YATM to properly handle runtime modifications to the input fields. i.e. to calculate humidity from dew point temperature. |
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Just wondering if this is relevant to this development? https://confluence.ecmwf.int/display/CKB/ERA5%3A+large+10m+winds |
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This affects <160 spacetime points in the whole dataset, so it seems a smaller issue than the backwards cyclones in JRA55 #186 |
… can be calculated on the fly. COSIMA/access-om2#242
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For reference, here are all the variables in
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Here are the biases in the monthly 1993-2017 climatology of JRA55-do 1.4.0 JRA55-do is very much warmer (>30 degrees!) over Antarctica, and also has positive and negative biases of around 5 degrees extending into the Southern Ocean in winter and spring. I imagine this is mostly due to the low-temperature cutoff applied to Antarctic temperature, and smoothing in the marginal ice zone (see sec 3.3.4 of Tsujino et al 2018 and below), but figs 6b and 7a show that these changes are purely positive in August over the Southern Ocean whereas we see a mix of positive and negative. Some of the difference could also be due to the differing measurement height. JRA55-do is cooler in the Arctic, especially in winter. Outside the polar regions it is a fraction of a degree warmer over oceans. The large difference in polar winters suggests significant differences in the representation of sea ice and its effect on the atmosphere.
Tsujino et al 2018 Fig 6: Tsujino et al 2018 Fig 7: |
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@aekiss Nice plots, this is really interesting. The high latitudes differences are obviously striking. I showed this at BoM this week. Paul Sandery was there and he pointed out that the very large positive (>10°C) biases in Antarctica appear to be over land, so perhaps the JRA55-do team didn't give that much consideration given it's meant for ocean models. Tsujino et al. appear to mask out land areas.
I understand the height difference is what made you analyse air temps first. Are you considering any similar analysis for other fields? At a Thursday meeting a few weeks back when this was discussed I think I recall @nichannah saying he felt he was close to a first run with ERA5. Is that the case? Or still a few things to resolve first? |
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Hi @scrallen, yes I'll also compare the other fields we will use to drive the model. @nichannah is converging on a working configuration but hit a few unexpected snags that required code changes. Also, we are yet to resolve how to shift the temperature from 2m to 10m, and calculate 10m |
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Hi Andrew
The method below gives the RH at a position where the dew point
temperature is known, but I don't know if that was part of the question.
For vertical shifting of these properties, are boundary layer similarity
relations the way to go?
Cheers,
Aviv
p.s.
In case it's of use, here is a method I used before for conversion of dew
point temperature Td to RH, albeit at the given height above ground. It's
based on the Tetens approximation for saturation vapor pressure, and on the
fact that *saturation* vapor pressure at the dew point Td is equal to the
actual vapor pressure (at the actual temperature T).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% %Use Tetens formula to get RH from (T,Td)
function RH = RH_from_DP(Td,T)
%obtain temperature T and Dew-point temperature Td in Kelvin
R3=17.502; R4=32.19; T0=273.15;
Pv = exp(R3.*(Td-T0)./(Td-R4)); %Actual vapor pressure [Pa] at
temperature T, by Tetens formula
Ev = exp(R3.*(T-T0)./(T-R4)); %Saturation vapor pressure [Pa] by Tetens
formula
RH = 100*(Pv./Ev); %[0-100]. Calculate relative humidity: ratio of
vapor pressure to saturation vapor pressure
RH(RH>100) = 100; RH(RH<0) = 0; % Correct some unphysical results of
the empirical formula
RH = RH/100; % if need 0-1 range
end
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Another useful reference on How to calculate hus at 2m (huss): https://confluence.ecmwf.int/pages/viewpage.action?pageId=171411214 |
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Thanks @avivsolo, that's helpful. I actually meant specific humidity (not relative), but Tetens' formula could be used for that too. |
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The ERA5 documentation https://confluence.ecmwf.int/display/CKB/ERA5%3A+data+documentation
Equations 7.4 and 7.5 from Part IV, Physical processes section (Chapter 7, section 7.2.1b) in the documentation of the IFS for CY41R2 are here
The constants in 7.4 are to be found in Chapter 12 (of Part IV: Physical processes): |
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Hi @nic, to help me get me head around this, I've made this summary of the mapping between JRA55-do and ERA5 forcing fields as currently in libaccessom2/tests/ERA5/forcing.json, in comparison with JRA55-do from here. I have several questions in the notes column. @russfiedler do you have any suggestions? Apologies if I'm digging up things that have already been discussed.
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Thanks @aekiss, this is very helpful. For now I've made the following improvements:
Regarding https://github.com/COSIMA/libaccessom2/blob/242-era5-support/libforcing/src/forcing_field.F90#L169 |
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OK let's see how that goes. |
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@aidan which field had one chunk for the whole month? I thought it was |
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@nichannah - re. ERA5 chunking and caching: you'll still get a performance speedup even if you need to read the same chunk more than once due to memory constraints on the size of the cache. e.g. a 8hr cache would speed it up by 8x even if chunks are larger than 8hr (ie even if chunks are read more than once). |
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@rmholmes can you add me to the NCI issue ticket? I raised the missing 1979 data almost a year ago (HELP-182126, 4 April 2022) and was told it was an upstream issue, but I'd have thought it would have been fixed upstream by now. |
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@aekiss oh sorry I hadn't seen that you'd asked exactly the same question. I've added you to the ticket and sent another message. |
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ERA5 winds are already at the right height (10m), but temp and humidity (from dew point) are at 2m and ideally should be moved to 10m to match. But this doesn't make much difference for temperature; not sure about humidity. There are other outstanding issues too - I'll pull together a summary. |
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Here's my attempt at summarising the remaining issues from this crazy-long thread:
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Thanks @aekiss!!! I just added one extra point on the caching code. I think it's also important to continue to make a value judgement on additional work in this direction given the possibility of a ERA-5-do product in the future, and the move to ACCESS-OM3/NuOPC framework. But I'm happy that we at least pushed it to the point of something that looks reasonable. |
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@rmholmes can you push your test run as a branch on my config https://github.com/COSIMA/1deg_era5_iaf pls? |
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Yes, but looks like I don't have the permissions to do that? The branch is at https://github.com/rmholmes/1deg_era5_iaf/tree/ryan_testing, or give me permissions? I should probably also create repositories on COSIMA for https://github.com/rmholmes/1deg_era5_ryf and https://github.com/rmholmes/025deg_era5_ryf? Finally, given Will's comments this morning it seems like it would be low hanging fruit and productive to setup a |
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This issue has been mentioned on ACCESS Hive Community Forum. There might be relevant details there: https://forum.access-hive.org.au/t/cosima-working-group-meeting-minutes-2023/407/9 |
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OK I've copied For https://github.com/rmholmes/1deg_era5_ryf and https://github.com/rmholmes/025deg_era5_ryf you can see if it will let you transfer ownership to COSIMA (settings > general > transfer ownership)
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Thanks for transferring ownership. This one's private - is that intentional? https://github.com/COSIMA/1deg_era5_ryf |
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Ooops. Fixed it. I've also setup a 1/4-degree IAF ERA5 (with JRA55 v1.5.0 run-off) (https://github.com/rmholmes/025deg_era5_iaf) and a corresponding JRA55 v1.5.0 run (https://github.com/rmholmes/025deg_jra55_iaf/tree/jra55v150), both to start in 1980. There's no hours to test these now but I'll kick them along at some stage. |
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Re. point 1 above, ACCESS-OM3 is using the DATM data atmosphere from CDEPS, which supports ERA5 out of the box. So that might teach us something useful about what fields we should use. This table suggests the ERA5 input fields are
The ERA5 DATM code is here and exports these fields to the other model components |
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The list of ERA5 input fields in DATM seems to omit visible radiation - or is that included in the |
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Some of those terms in your list @aekiss for the DATM look like a mirror of what the CESM would have been passing so they have converted the ERA5 into CESM look a like so it can run their shortwave scheme for instance over CICE. |
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@aekiss The visible radiation is in the shortwave radiation fields swvdr swvdf |
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Ah OK - might have to look at the code to see how shortwave is calculated from the input files |
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Yes @aekiss I think I need to look at the existing DATM code as well I have only looked at the DOCN and DICE boxes so far and how that fitted with CICE. Like my conversation with Kieran Ricardo the other day the way NUOPC is set up is still new to us and how we thought about things linked together before may need rethinking I guess we need to think how the UM will link to an ACCESS_OM3 MOM/CICE/WW3 as well as the JRA55 and ERA set ups in the data model. |
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I did a quick check of the radiation and precipitation variables (points 1 and 4 at #242 (comment)). Just for a single day, but looking reasonable to me: |
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@rmholmes and others. Your experiences with ERA5 and JRA55 will be valuable as NCAR, GFDL, and interested others start the process of developing an "ERA5-do". I hope we can count on you for testing new forcing fields when they are ready. Gokhan is in charge at NCAR. He hopes to have something for beta-testing early 2024. |
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Great to hear ERA5-do is going ahead @StephenGriffies. I'll be interested in testing this in ACCESS-OM3 when it's ready too. |
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Thanks for looking at those field @rmholmes - I agree they don't look very different. My worry was whether exactly the same things are included in both cases, e.g. the same wavelength bands and diffuse/direct for shortwave, or the same precip types. This might only show up on maybe a 10% level, which is harder to test as the fields might differ by this amount between JRA55 and ERA5 anyway even if they're trying to show exactly the same things. Might require diving into documentation. |
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ERA5 has a list of known issues here https://confluence.ecmwf.int/display/CKB/ERA5%3A+data+documentation#ERA5:datadocumentation-Knownissues |
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NCI also has a table of ERA5 data issues here https://opus.nci.org.au/display/ERA5/Known+Issues |
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I have now finished a 1/4-degree ERA-5 forced IAF run, covering the period from 1980 up to the latest available forcing time of 31st of March 2023. The main problem I ran into is blow-ups under unrealistically large ERA-5 winds (up to 130ms-1) as described in this ACCESS-OM2 issue and this ECMWF post. Getting past them involved scaling down the strength of the wind fields using the offset/scaling system in libaccessom2 and this notebook. A quick look at the output is looking promising (IAF runs, and RYF runs). I hope to do a more detailed analysis and will put up a forum post at some point asking for input from anyone who is interested. |
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Awesome, thanks @rmholmes! |
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This issue has been mentioned on ACCESS Hive Community Forum. There might be relevant details there: https://forum.access-hive.org.au/t/era-5-forced-access-om2-simulations/1103/1 |
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This issue has been mentioned on ACCESS Hive Community Forum. There might be relevant details there: https://forum.access-hive.org.au/t/jra-3q-as-a-replacement-for-jra55/1759/8 |
This issue is a continuation of an email discussion on making configurations that support ERA5 forcing, e.g. to assess the impact of the forcing dataset on the sea ice simulation.
ERA5 is available on NCI at
/g/data/rt52: https://opus.nci.org.au/display/ERA5/ERA5+Community+Home[edit: use/g/data/ik11/inputs/ERA5instead]Replacing JRA55-do with ERA5 would require
and changes to
and possibly more, e.g.
Our configurations currently support only JRA55-do forcing: https://github.com/COSIMA/access-om2/tree/master/control
but we have some old, unsupported CORE configs here that may be useful as a reference for the changes required
https://github.com/COSIMA/1deg_core_nyf
https://github.com/COSIMA/025deg_core2_nyf
https://github.com/COSIMA/025deg_core_nyf
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