How to downlod the data directly from the Parameter database

Datasets and Usage C3S - Datasets and Usage
1

Hi, I need some variables which could have the information about gravity waves.
For that I explored the Parameter database of ECMWF (Parameter Database) I believe that it also come usee the ERA5 datasets.

For example I have selected the parameter which comes under our interest to download “U-tendency from subgrid orography”. Unfortunately we don’t have the description of the data (Parameter Database). Therefore, It difficult to write the script to download the data. I tried following script, and it showed error. Please suggest me, how to download this variable.

import cdsapi

c = cdsapi.Client()

c.retrieve(
‘reanalysis-era5-complete’,
{
‘product_type’: ‘reanalysis’,
‘variable’: [‘U-tendency from subgrid orography’],
‘year’: [‘2020’ ],
‘month’: [‘01’ ],
‘date’: [ ‘01’,],
‘format’: ‘grib’,
},
‘download2.grib’)

MARS has returned an error, please check your selection.
Request submitted to the MARS server:
[{‘day’: [‘01’], ‘month’: [‘01’], ‘product_type’: ‘reanalysis’, ‘variable’: [‘U-tendency from subgrid orography’], ‘year’: [‘2020’], ‘class’: [‘ea’], ‘expver’: [‘1’], ‘database’: ‘fdbmarser’}]
Full error message:
mars - ERROR - 20250218.150428 - Ambiguous parameter: day could be DATE or DATABASE
mars - ERROR - 20250218.150428 - undefined value : reanalysis for parameter PRODUCT
mars - ERROR - 20250218.150428 - Values are :
mars - ERROR - 20250218.150428 - undefined value : U-tendency from subgrid orography for parameter VERIFY
mars - ERROR - 20250218.150428 - Values are :

The job failed with: MarsRuntimeError

2

Hi,
the complete list of parameters available on ERA5 model levels are available at the following link, table 12 and 13: ERA5: data documentation - Copernicus Knowledge Base - ECMWF Confluence Wiki

Thanks

3

Hi Michela,

Thank you so much for your reply.

I am looking for data on the variables “U-tendency from subgrid orography” and “V-tendency from non-orographic wave drag.” As you suggested, I checked Tables 12 and 13 in this link.

I found a variable named “Mean eastward wind tendency due to parametrisations” and successfully downloaded the data using the following script:

import cdsapi
c = cdsapi.Client()
c.retrieve('reanalysis-era5-complete', { 
   'date'    : '2013-01-01',            
   'levelist': '1/10/100/137',          
   'levtype' : 'ml',
   'param'   : '235007',                   
   'stream'  : 'moda',                  
   'time'    : '00/to/23/by/6',         
   'type'    : 'fc',
   'area'    : '80/-50/-25/0',          
   'grid'    : '1.0/1.0',               
   'format'  : 'netcdf',                
}, 'ERA5-ml-235007-subarea.nc')

However, when I change the ‘param’ value to retrieve “U-tendency from subgrid orography,” the script does not work and throws an error. Since the website provides limited information on this parameter, I am unsure how to modify the script to download this data correctly.

Could you confirm whether “Mean eastward wind tendency due to parametrisations” in Table 13 corresponds to “U-tendency from subgrid orography”? The term “parametrisations” is quite general, does it include this specific?

I would appreciate any guidance on how to proceed.

Thank you for your time and support.

Kind regards,
Anish

4

Hi Amish,

Unfortunately, U-tendency from subgrid orography is not an ERA-5 parameter.

The parameter database that you refer to is intended to support the ecCodes software and, as such, contains more parameters than is currently available in any single datastore.

U-tendency of subgrid orography is not a parameter that is currently available for retrieval in any open data catalogue.

Can you tell me a bit more about what you’re looking for?

Thanks,
Emma

5

Hi Emma,

Thank you for the clarification.

We lack observational data on gravity wave (GW) forcing, ideally in the form of gravity wave drag. While the ERA5 dataset provides parameterized subgrid-scale GW forcing, we have only been able to access the total column GW dissipation (gravity_wave_dissipation, GWD, 197). We are currently working on obtaining a vertically resolved field from them, but an ERA5 dataset with vertically resolved GW drag due to dissipation would be ideal. Our focus is on the lower stratosphere, particularly in the Himalayan hotspot region. Specifically, we are interested in the climatology of GW drag and its anomalies in certain years.

Please let me know if you can suggest any relevant data.

I also have a question about the “Mean eastward wind tendency due to parametrisations” in Table 13. Could you provide more details on this?

Kind regards,
Anish

6

Hi Anish,

For vertically resolved gravity wave drag, ERA5 does not archive separate GW drag profiles. However, the relevant information is included in the “Time-mean eastward/northward wind tendency due to parametrization” fields, which are available at model levels in the ERA5 forecast data. These correspond to Parameter IDs 235007 (eastward) and 235008 (northward).

This variable combines tendencies from:

  • Orographic and non-orographic gravity wave drag
  • Vertical diffusion parametrization
  • Convective momentum transport

Since your focus is on the lower stratosphere in the Himalayan hotspot region, the main contributors in that area will likely be gravity wave drag and vertical diffusion.

The data you are trying to access is on MARS tapes, but the access is still via the cdsapi. You need to follow the instructions here How to download ERA5, in particular section 4, option B.

I’ve also provided a link to the relevant area where these parameters can be found in our ERA Catalogue here.

I hope this helps! Let me know if you need further details.

Best wishes,
Emma