[Go-essp-tech] Global attributes and DRS extensions for downscaled datasets
Karl Taylor
taylor13 at llnl.gov
Tue Mar 26 18:51:17 MDT 2013
Dear Martin,
I'm not advocating changing the CORDEX requirements; it's probably much
too late for that. There are are limitations to the generality of the
CORDEX specifications, which means they might not be applicable to
downscaling efforts outside of CORDEX. The document I prepared was to
try to address the more general issue of what descriptors are needed for
downscaled datasets.
I have proposed that a single additional "descriptor" be added to the
already defined components of the DRS:
Source of predictor data ? driving_model_id - driving_model_rip (e.g.
"GFDL-CM3-r1i1p1") In some cases the driving_model_rip might be
omitted (e.g., when using reanalysis output to drive the downscaling).
In CORDEX this descriptor could be formed by joining with a hyphen your
GCMModelName and CMIP5EnsembleMember.
I have also proposed expanding the "ensemble member" descriptor to
include an indication of the "nominal resolution". The idea here is
that output might need to be regridded or be made available at various
resolutions, so we would like to be able to distinguish among these
closely related datasets. Here is the description of the 'riph' designator:
Ensemble member? 'riph' designator, where the "rip" form is defined
as in CMIP5 (which for downscaled data would usually be "r1i1p1"), and
the "h" is followed by nominal resolution expressed in kilometers.
(For backward compatibility the DRS would consider the "h" segment as
optional, but it is required for downscaled datasets.) The last part of
the 'riph' designator is of the form "hnXXXX" or "hiXXXX" where XXXX is
the nominal horizontal resolution of the downscaled data, expressed in
kilometers (rounded to the nearest km with leading zeros dropped). "hn"
indicates that the data is stored on the model's "native" grid, while
"hi" indicates that the data has been interpolated from a model's native
grid to a different grid. (Statistically downscaled data would normally
be recorded on a so-called "native" grid.) Data on a native grid at a
nominal resolution of 5 km, for example, would be identified as "hn5",
while regridded data at 11 km resolution would be identified as "hi11".
The XXXX should be calculated as follows: XXXX = sqrt(domain area /
(number of grid cells)), expressed in km/grid cell and rounded off to
the nearest km.
CORDEX has chosen to include resolution information as part of a domain
name (e.g., CAM-44 or SAM-44i), but the resolution doesn't seem to me to
belong as part of the region identification.
I should note also that CORDEX specifies a directory structure and/or
filenames where in the CORDEX document some of the DRS categories are
renamed. I've attached a table that shows the DRS elements and
corresponding CORDEX identifiers, along with global attributes. (I'm
going to try to get NASA / NOAA to be consistent with the DRS.) I also
provide a table of additional global attributes. CORDEX is mostly
consistent with this table, except for using "CORDEX_domain and omitting
driving_model_tracking_ids.
Finally, I note that in the example found in the CORDEX document for
global attributes:
1) experiment_id = "evaluation", but in the directory structure and
filename templates, this is presumably used as "CMIP5ExperimentName",
but of course "evaluation" is not a CMIP5 experiment. I think a better
term for "CMIP5ExperimentName" is simply "experiment", which in the case
of CORDEX is usually the same as the CMIP5 experiment_id.
2) CORDEX requires "contact", but this was left out of the example.
Please let me know what you think.
Best regards,
Karl
On 3/26/13 4:58 AM, martin.juckes at stfc.ac.uk wrote:
>
> Hello Karl,
>
> I'm puzzled about how this fits in with CORDEX. We went through this
> discussion some time ago, and agreed on some data requirements in the
> document you cite below which we believed to be appropriately
> consistent with the CMIP5 requirements. This document was then
> discussed at a WCRP meeting and has been circulated as the
> requirements for groups submitting CORDEX data to ESGF. Since then,
> modelling groups have been preparing data and we are expecting to
> start publication soon. Do you think there are problems with
> uniformity in the way the CORDEX requirements are specified?
>
> Regards,
>
> Martin
>
> *From:*Karl Taylor [mailto:taylor13 at llnl.gov]
> *Sent:* 25 March 2013 21:50
> *To:* Galia Guentchev
> *Cc:* ncpp_core at list.woc.noaa.gov; NCPP TECHNICAL TEAM;
> go-essp-tech at ucar.edu; laura.e.carriere at nasa.gov; Potter, Gerald Lee.
> (GSFC-606.2)[UNIVERSITY OF MARYLAND]; Dean Williams; Nadeau, Denis
> (GSFC-610.1)[R S INFORMATION SYSTEMS, ]; Juckes, Martin
> (STFC,RAL,RALSP); Pascoe, Stephen (STFC,RAL,RALSP)
> *Subject:* Global attributes and DRS extensions for downscaled datasets
>
> Dear all,
>
> I have spent considerable time reviewing the following four documents:
>
> A. The email (copied below) sent by Galia and Aparna, which proposed
> attributes, filenames, and directory structures for downscaled data.
>
> B.
> http://cmip-pcmdi.llnl.gov/cmip5/docs/cmip5_data_reference_syntax.pdf
> which describes the corresponding CMIP5 metadata.
>
> C.
> http://cordex.dmi.dk/joomla/images/CORDEX/cordex_archive_specifications.pdf
> <http://cordex.dmi.dk/joomla/images/CORDEX/cordex_archive_specifications_121022.pdf>
> which describes the corresponding CORDEX metadata.
>
> D.
> http://cmip-pcmdi.llnl.gov/cmip5/docs/CMIP5_output_metadata_requirements.pdf
> which specifies all the CMIP5 metadata requirements.
>
> I hope that document A above could be made compatible with the others
> and in general could provide a sound basis for establishing more
> uniformity moving forward. Toward that end, I have prepared the
> attached document describing for downscaled data a minimal set of
> global attributes needed to augment those used in CMIP5 and also the
> extensions needed to the DRS document to accommodate downscaled data.
>
> I hope at least a few of you will take the time to study this document
> and provide feedback.
>
> Best regards,
> Karl
>
>
> Mail sent by Galia Guentchev 3/12/13
>
> **********************************************************************
> Details of each element of the proposed directory structure:
>
> Proposed elements -
> /projectID/sub-project/product/institution/*predictorModel/experimentID/frequency/realm/MIPtable/Pred
> ictor_experiment_rip/predictorversion*//downscalingMethod/predictand
> (variableName)/region///DownscaledDataversion//file_name.nc
>
> Example:
>
> /ncpp2013/perfectModel/downscaled/NOAA-GFDL/*GFDL-HIRAM-C360-coarsened/amip/day/atmos/day/r1i1p1/v20121024*//GFDL-ARRMv1/tasmax/US48/v20120227//tasmax_day_amip_r1i1p1_downscaled_US48_GFDLARRMv1_19790101-19831231.nc
>
> The new element sub-project (in blue above) gives the opportunity to
> indicate to users that in the one case the method was trained on
> observations (standard setting), and in the other on model that was
> considered to be the truth (perfect model setting);
> The options there could be: PerfectModel or Standard - where possibly
> there could be a different name instead of 'standard' for the standard
> downscaling setting.
>
> For NASA datasets some of the directories could be:
>
> project = NEX
> product = downscaled
> institution = NASA-Ames
> predictorModel - original model value
> experimentID = historical
> frequency = mon
> realm = atmos
> Predictor_experiment_rip - original model value
> variable = precipitation or temperature
> region = CONUS
>
> DownscalingMethod will also be included as a directory to allow for
> search on method.
>
> **********************
> There are a set of sub-directories that refer to the _PredictorModel_
> - presented in bold -
> */predictorModel/experimentID/frequency/realm/MIPtable/Pred
> ictor_experiment_rip/predictorversion*
>
> Where:
>
> ·predictor model - is the specific GCM which is the source of the
> predictor data set - GFDL-HIRAM-C360-coarsened - in the above example
>
> ·experimentID - the specific experiment - amip in this case
>
> ·frequency - refers to the temporal scale of the predictor fields - daily
>
> ·realm - the realm of the predictors - in this case atmos(phere)
>
> ·MIPtable - name of the model intercomparison table - daily in this
> example, could be amon - for atm monthly data;
>
> ·Predictor-Experiment-rip - follows the standard notation from CMIP5
>
> ·version - the version date of the global model that provided the
> predictor dataset
>
> The elements above follow quite closely the structure for CMIP5 model
> output directory elements.
>
> There is a set of sub-directories that refer to the Downscaling method
> - presented in italics -
> /downscalingMethod/predictand (variableName)/region/DownscaledDataversion
>
> /Where:
>
> ·downscalingMethod - is the downscaling method abbreviation - in this
> case GFDL-ARRMv1 - the GFDL in the name indicates that this is a
> setting applied by GFDL where there were two sets of predictors, based
> on the ARRM method of K.Hayhoe; also v.1 indicates which version of
> the ARRM method was used (the original version) - more details about
> the method are given in the global attributes of the file;
>
> ·Predictand (variableName) - the specific predictand variable that was
> downscaled; tasmax in this case;
>
> ·region - indicates that the method was applied to the US48
>
> ·DownscaledDataversion - the version of the downscaled dataset
>
> *For the purposes of standardization there are two directions to
> consider:*
>
> 1) One is to have*one standard directory* structure that will be used
> by all - for example, following the example of GFDL to have the
> details of the predictor model first and then the downscaling method
> details:
>
> ·ProjectID - sub-project - product - Institution - Predictor dataset
> details - Downscaling method details - Filename
>
> Having a standardized approach would help any automated service/web
> service to detect the directory path for a particular dataset.
>
> 2) During our last teleconference there was a proposal to follow the
> downscaling practice and describe the downscaling method first and
> then the predictor model. This leads to *two paths*:
>
> . ProjectID - _Standard or Perfect Model sub-project facet_-
> product - Institution - then see below:
> - (if Perfect model setting) Predictor dataset details
> - Downscaling method details,
> - (if Standard setting) - Downscaling method details -
> Predictor dataset details
>
>
> The NCPP Core team accepts that it may be reasonable to have a
> directory structure - where the method description is first; and
> another directory structure - where the predictor description is first
> and then the methods that are applied are described; *NCPP will
> support either approach* (one overall directory structure, or two
> separate pathways) and if the second approach is chosen (with two
> different sub-directory sequences) - we would like to promote and to
> support the standardization of these different directory pathways -
> meaning - we will support two standardized directory structures to
> accommodate two common practices.
>
> ******************
> Additional details:
>
> *Variable level attributes-*
> The published dataset should also conform to CF-standards.
> eg-
>
> tasmax:long_name = "Downscaled Daily Maximum
> Near-Surface Air Temperature" ;
> tasmax:units = "K" ;
> tasmax:missing_value = 1.e+20f ;
> tasmax:_FillValue = 1.e+20f ;
> tasmax:standard_name = "air_temperature" ;
> tasmax:original_units = "K" ;
> * tasmax:downscaling_method: GFDL-ARRMv1*
>
> *Global attributes- *listing a few here, several CMIP-style attributes
> will be inherited.
>
> "predictorModel" will replace "model_id"
> For the 'downscaling model', as agreed with Luca on the call it
> would be 'downscalingMethod'
>
> :Conventions = "CF-1.4" ;
> :references = "info about model, training datasets etc
> will be provided here"
> :info = "additional info about the downscaling method"
> :creation_date = "2011-08-19T21:57:06Z" ;
> :institution = "NOAA GFDL(201 Forrestal Rd, Princeton,
> NJ, 08540)" ;
> :history = "info on file processing. Eg" processed by
> toolX." ;
> :projectID = ncpp2013
> :subprojectID = perfectModel
> :product = downscaled
> :institution = NOAA-GFDL
> :predictorModel = GFDL-HIRAM-C360-coarsened
> :experimentID = amip
> :frequency = day
> :modeling_realm = atmos
> :Predictor_experiment_rip = r1i1p1
> :region = US48
> :table_id = day
> :version = v20120227
> :downscalingMethod = GFDL-ARRMv1
> **************************************************
>
> Best regards,
> Galia and Aparna
>
>
> --
> Galia Guentchev, PhD
> Project Scientist
> National CLimate
> Predictions and
> Projections
> Platform (NCPP)
> NCAR RAL CSAP
> FL2 3103
> 3450 Mitchell Lane
> Boulder, CO, 80301
> phone: 303 497 2743
>
>
> --
> Scanned by iCritical.
>
>
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