AUS2200 hybrid height coordinate

Atmosphere AUS2200
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1

Hi, I was wondering if anyone could provide some insight on the vertical coordinate provided in the published AUS2200 data.

For example, in the file

/g/data/bs94/AUS2200/mjo-neutral2013/v1-0/1hr/ua/ua_AUS2200_mjo-neutral_1hrPt_201303011900-201303020000.nc

the vertical dimension is atmosphere_hybrid_height_coordinate, in metres, with 66 levels having values:

lev = 2.4999996, 13.333332, 33.333332, 60, 93.33332, 133.33332, 180, 233.33332, 293.33332, ...

I guess my question is what do these values represent? Height above the surface, or something else? I canā€™t really find anything in the metadata to indicate this. And if the coordinate does not represent height above the surface, is there a a way to correct for this with the available data?

Thanks, Andrew

2

Thereā€™s a description of how UM model levels work at Vertical Coordinates - climate-cms wikis.unsw.edu.au. Levels closer to the surface follow orography, levels higher up are at fixed heights.

Your hybrid_height_coordinate is probably Zsea in the linked equations, there should be a second field in the file for C that goes from 1 at low levels to 0 at high levels.

3

Thanks for this reply, Scott

That makes sense - although I canā€™t see any field for C in the netcdf file or in the published AUS2200 directories, or even for the eta levels and first_constant_rho_level that I suppose could be used to calculate C? (from Appendix A here)

4

See the files in ~access/umdir/vn13.8/ctldata/vert for eta values for standard level sets - 66 levels is an odd count though so they may have done custom levels for the aus2200 runs?

5

Iā€™ll note that the data has been post-processed using MOPPeR (ā€œpost-processed using ACCESS-MOPPeR v0.6.0ā€ in the metadata), so I guess the vertical levels could have been truncated and/or converted within that

6

Thereā€™s a link to the CMIP6 grids and coordinate tables on the MOPPeR documentation page - but the page is also copyrighted to Pao and Sam so you might get the fastest answer by reaching out to either or both!

7

Thanks Bethan. @sam.green @paocorrales are you able to provide any information?

8

This is correct as I was able to reconstruct the hybrid_height_coordinate in the published netcdf file by using the eta_rho values in the vertlevs_L70_61t_9s_40km levset and the formula for Zsea given here.

So I should be able to now calculate the height above surface from Zsea and calculating C from the levset file, and using the orography file that is in the published AUS2200 directory.

These steps are not very obvious/straightforward, I wonder if some information can be provided to users of the published data somehow? I can put a recipe on the ACCESS cookbook, at the least.

9

In this case is @Paola-CMS the right person to ask :wink:

10

Whoops! Apologies Pao/Paola

1 Like
11

Hmm this seems specific to the aus2200 data, not the post-processing by MOPPeR/CMOR3. Your best bet is Paola or Dale answering this question as they were involved in the AUS2200 runs

12

Looking at the cf conventions for hybrid height levels there should be a formula_terms attribute on the standard_name="atmosphere_hybrid_height_coordinate" variable that points at the name of the C variable. Is this present in the file? If not thatā€™s probably a useful enhancement for the post-processor.

13

@andrewb1 yes, you should be able to calculate height above surface from that.

Agree it would be good to have a page explaining this somewhere with the dataset.

14

Is this present in the file?

Not that I can see, but Iā€™ll just paste the metadata here in case Iā€™m missing something obvious

netcdf ua_AUS2200_mjo-neutral_1hrPt_201303011900-201303020000 {
dimensions:
	time = UNLIMITED ; // (6 currently)
	lev = 66 ;
	lat = 2120 ;
	lon = 2600 ;
	bnds = 2 ;
variables:
	double time(time) ;
		time:units = "days since 1970-01-01" ;
		time:calendar = "proleptic_gregorian" ;
		time:axis = "T" ;
		time:long_name = "time" ;
		time:standard_name = "time" ;
	double lev(lev) ;
		lev:bounds = "lev_bnds" ;
		lev:units = "m" ;
		lev:axis = "Z" ;
		lev:positive = "up" ;
		lev:long_name = "hybrid height coordinate" ;
		lev:standard_name = "atmosphere_hybrid_height_coordinate" ;
	double lev_bnds(lev, bnds) ;
	double lat(lat) ;
		lat:bounds = "lat_bnds" ;
		lat:units = "degrees_north" ;
		lat:axis = "Y" ;
		lat:long_name = "Latitude" ;
		lat:standard_name = "latitude" ;
	double lat_bnds(lat, bnds) ;
	double lon(lon) ;
		lon:bounds = "lon_bnds" ;
		lon:units = "degrees_east" ;
		lon:axis = "X" ;
		lon:long_name = "Longitude" ;
		lon:standard_name = "longitude" ;
	double lon_bnds(lon, bnds) ;
	float ua(time, lev, lat, lon) ;
		ua:standard_name = "eastward_wind" ;
		ua:long_name = "Eastward Wind" ;
		ua:comment = "Zonal wind (positive in a eastward direction)." ;
		ua:units = "m s-1" ;
		ua:cell_methods = "time: point" ;
		ua:history = "2023-10-23T05:56:00Z altered by CMOR: replaced missing value flag (9.96921e+36) and corresponding data with standard missing value (1e+20)." ;
		ua:missing_value = 1.e+20f ;
		ua:_FillValue = 1.e+20f ;
		ua:coverage_content_type = "modelResult" ;

// global attributes:
		:Conventions = "CF-1.7 ACDD1.3" ;
		:creation_date = "2023-10-23T05:56:25Z" ;
		:data_specs_version = "01.00.00" ;
		:date_created = "2023-06-11" ;
		:exp_description = "A limited area model study of the entire Australian continent at 2.2 km resolution, using the UM atmospheric model. ERA5, ERA5Land and BARRA-R for soil moisture only reanalysis data was used to provide initial and boundary conditions. The study covers a complete Madden-Julian Oscillation event during a neutral phase in January-February 2013." ;
		:forcing = "GHG, Oz, SA, Sl, Vl, BC, OC, (GHG = CO2, N2O, CH4, CFC11, CFC12, CFC113, HCFC22, HFC125, HFC134a)" ;
		:geospatial_lat_max = "-6.83" ;
		:geospatial_lat_min = "-48.79" ;
		:geospatial_lon_max = "158.98" ;
		:geospatial_lon_min = "107.52" ;
		:grid = "native atmosphere grid (2120x2600 latxlon)" ;
		:institution = "University of Melbourne" ;
		:keywords = "Climate change processes, Adverse weather events, Cloud physics" ;
		:nominal_resolution = "2.2 km" ;
		:organisation = "Centre of Excellence for Climate Extremes" ;
		:product = "model-output" ;
		:product_version = "v1.0" ;
		:realm = "atmos" ;
		:source = "UM v12.2 ECMWF ERA5, ERA5-Land and BARRA-R (for soil moisture) reanalysis fields used as forcings" ;
		:source_id = "AUS2200" ;
		:table_id = "A1hr" ;
		:table_info = "Creation Date:(20 June 2023) MD5:fd3de836c2eb45864aab0211f52f6ce4" ;
		:time_coverage_end = "2013-03-01" ;
		:time_coverage_start = "2013-01-01" ;
		:variable_id = "ua" ;
		:version = "v1.0" ;
		:license = "https://creativecommons.org/licenses/by/4.0/" ;
		:cmor_version = "3.7.1" ;
		:tracking_id = "e15bd7e0-373b-416c-8d99-03586df2c1d3" ;
		:title = "AUS2200 Unified Model atmospheric simulation of a Madden-Julian Oscillation event during a neutral phase, Jan and Feb 2013, over Australia at 2.2km resolution." ;
		:frequency = "10minPt" ;
		:experiment_id = "mjo-neutral2013" ;
		:experiment = "mjo-neutral2013" ;
		:creator_name = "Dale Roberts, Paola Petrelli, Claire Vincent" ;
		:creator_role = "model simulation, post-processing, principal investigator" ;
		:creator_url = "https://orcid.org/0000-0003-3952-6344, https://orcid.org/0000-0002-0164-5105,  https://orcid.org/0000-0001-5315-1644" ;
		:contact = "claire.vincent@unimelb.edu.au" ;
		:comment = "post-processed using ACCESS-MOPPeR v0.6.0 https://doi.org/10.5281/zenodo.10976467" ;
		:publisher_name = "NCI" ;
		:publisher_email = "help@nci.org.au" ;
		:id = "https://doi.org/10.25194/gprx-2d45" ;
		:citation = "Roberts, Dale, Petrelli, Paola, Vincent, Claire. AUS2200 Unified Model atmospheric simulation of a Madden-Julian Oscillation event during a neutral phase, Jan and Feb 2013, over Australia at 2.2km resolution v1.0 (2024). NCI Australia. (Dataset) https://doi.org/10.25914/gprx-2d45" ;
		:creator_email = "dale.roberts1@anu.edu.au, paola.petrelli@utas.edu.au, claire.vincent@unimelb.edu.au" ;
		:history = "2023-10-22T03:39:20Z ; CMOR rewrote data to be consistent with , CF-1.7 ACDD1.3 and CF standards." ;
}
1 Like
15

@andrewb1 " The values of Zsea and C are also available in the LOOKUP header of UM output files, as values blev and bhlev respectively."

They donā€™t look like theyā€™re in your header metadata :frowning:

16

So, it seems like some relevant metadata has been lost from the UM files on post processing, which makes converting hybrid height coordinates to height above surface a little tricky.

As a temporary solution Iā€™m adding a recipe to the atmosphere cookbook (someone can review the PR if they want) with a workaround for the missing metadata.

I suppose a more long term solution would be to add the metadata back somehow, and/or to make some changes to the post-processing software

17

Pinging @dale.roberts might work ā€¦ :crossed_fingers:

18

Hi @andrewb1 Thanks for your post - I am just marking this as out of scope for ACCESS-NRI triage admin purposes but looks like there is lots of help available so please continue the discussion.

1 Like
19

Hi @Aidan and all. Apologies for taking a while to respond, I had to dig through quite a few archived emails for the answers to this. So, the easy question, why 66 levels? When we started getting the post-processed data together, we had very little permanent storage, so there was some back and forth getting an agreement on what was necessary vs what was nice to have. I found an email dated 28/8/23 stating ā€˜We can remove everything for the uppermost four model levels (i.e. 28985.46, 32192.732, 35845.004, 40000)ā€™. Thatā€™s easy to do, drops the file size by a few percent and seemed sensible, so Paola did as instructed. I guess this instruction was never widely circulated? I certainly forgot about it.

As for the second question, regarding missing metadata, I donā€™t know. I couldnā€™t find anything in my emails about that. I suspect the answer is a confluence of the factors posted above, maybe CMOR/CF compliance limits the metadata in the file? If that is the case maybe that metadata lives elsewhere by necessity? Maybe no one ever asked and so it was never done? I do recall doing work around getting fields onto pressure levels, but not altitude. Although I do recall plotting altitude from UM data once, but that might have just been playing around? The only person who would know CMOR/CF that well and would have the records of the AUS2200 post processing is Paola.

4 Likes
20

Thanks for digging into this, @dale.roberts!