FAQ - WDCC User Interface & Download
If you experience problems or need assistance please contact us via
firstname.lastname@example.org. A ticketing system will acknowlegde your enquiry and generally your request will be processed within one working day. When sending attachments (i.e. screenshots) please bear in mind that the ticketing system will only accept mails up to 3MB in size.
For an overview of the current status of the WDCC's and DKRZ's services please visit https://status.dkrz.de/.
Accounts & Password
How do I get access to the WDCC?
Please fill out the form at https://cera-www.dkrz.de/WDCC/ui/cerasearch/register or send an email containing your name and institute affiliation to
email@example.com. You will receive the account details when your request has been processed (usually within one working day).
How can I reset a lost password?
firstname.lastname@example.org reset your password.
How can I change my password?
The password can be changed after login on this page: https://cera-www.dkrz.de/WDCC/ui/cerasearch/changePassword.
How is the data licensed?
All data and pages available from WDCC are licensed under a Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/2.0/de/deed.en) as far as those conditions are not in any way modified by the following conditions or by any conditions specific to data or pages. For more detail see 'Conditions WDCC Database': http://terms.wdc-climate.de/
How to cite data?
Citation information can be found via webbrowser using the WDCC user interface (http://cera.wdc-climate.de/):
- Enter the name or acronym of the entry into the search box and click on the magnifying glass
- Click the blue label (e.g. 'Experiment' or 'Dataset Group') in the result list to open the landing page
- The citation information can be found in the 'Cite as' block of the metadata page. You may also use the auto-generated BibTeX and RIS exports in order to transform the citation in a style of your choice.
For more information see also: http://www.komfor.net/cite-data.html
Data download in general
How can I access data stored in the WDCC?
WDCC datasets can either be downloaded via webbrowser using the web interface or with the Java-based commandline tool Jblob that can be used on any OS supporting Java ( Oracle or OpenJDK ).
I created an account but I still don't have permissions to download a specific dataset
Some data providers do not wish for their datasets to be publicly available and only grant permission after approval. Please check the 'Access constraints' point at the landing page of the desired dataset to find out what to do. If there are no clear instructions at this point, please contact us at
email@example.com a short description of what you intend to do with the data and we will get in touch with the data provider.
Is it possible to select temporal subsets during data download?
Both the WDCC web interface and Jblob generally offer the ability to select temporal subsets of stored data by specifying start and end dates. The granularity is based on how the data is stored in our database, e.g. the smallest downloadable time span for a dataset that is stored in monthly records is one month.
Is it possible to select a geographic region during data download?
Jblob offers a subset of cdo processing capabilities, including selection of a geographic region, please take a look at the Jblob documentation for more information. Regional selection from the interactive download is currently not possible.
Can the data format be changed during download (i.e. Grib => NetCDF)?
Currently it is not possible to change a dataset's format during download.
Can wget be used to download data from WDCC?
Wget access is currently not supported.
What is the maximum size of downloads?
Currently a maximum of 16TB can be downloaded or selected for processing in a single request.
Can I get more information about the datasets stored within the WDCC ?
For many datasets supplementary information is available in the form of "additional_info"-type entries (these can be found in the data hierarchy) or individually stored detailed data headers. The data headers (if available) can be accessed from the dataset's metadata information page by clicking on the "Data headers" button in the 'General information' section.
Data download speed and access times
Why does it take so long before the download actually starts?
A large part of the datasets available the WDCC are stored on tapes and have to be retrieved to a local disk cache before the actual transfer. Only downloads for datasets that are currently present in the disk cache will start immediately. It is not necessary to start a download again if the first request ist still active but hasn't transferred anything yet.
How long will it take to transfer data stored on tapes?
The tape access delay depends on the current workload of our archive subsystem, usually the transfer from tape to disk cache will start within 5-10 minutes. The transfer speed between tapes and disk cache is 100-120 MB/s. Please keep in mind that datasets in the WDCC are stored within special "containers" that may be larger than the dataset itself, so the transfer of a 1 GB dataset might take longer if it is archived within a 100 GB container. The same applies for downloading temporal subsets of datasets.
How long will it take to process data during download?
Data processing during download currently is done in 3 separate steps. First, the datasets is retrieved from tapes (if necessary) and the selected time steps are merged into a single file. Afterwards the cdo processing will take place and finally the result file will be tranferred to the user. The resulting idle time before the download actually starts may be up to several hours, e.g. when extracting smaller areas or sinlge variables from very large / multi-variable datasets.
WDCC user interface
How many parallel downloads can I start?
Please limit the number of parallel downloads to 4. If you need to download large numbers of datasets please take a look at our batch download toolJblob and create a script for chain-downloads of datasets. Additionally there is a feature available on many list page that allows you to download .csv lists for script generation and/or pre-defined Jblob download scripts.
Are download managers (including browser add-ons) supported?
Download managers are not supported, if you need to use them regardless please configure a retry interval of at least 60 seconds and limit the number of parallel downloads to 4. If usage of a download manager results in too many request in a very short time your account may be temporarily blocked!
How many parallel downloads can I start?
Please limit the number of parallel downloads to 4 and the number of processing (cdo) requests to 1 when processing very large datasets.
How do I know if my Jblob download was successful?
Please check the return value of the Jblob call. A return code of 0 is a successful transfer, any other value indicates a problem during data download. Please take a look at the Jblob documentation for a description of the different exit values.
How can I use Jblob on DKRZ's mistral system?
Jblob is accessible on mistral via the module 'jblob', you only need to load the module by executing
module load jbloband this will add the binary to your search path and prepare the Java environment.
Common Jblob error messages
cdo(2) sellonlatbox (Abort): Unsupported grid type!
In most cases appending
--cdo "selgridname,gaussian"to the processing request will avoid the error, e.g.
jblob --dataset <acronym> --cdo "sellonlatbox,0,180,0,90" --cdo "selgridname,gaussian"