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Figure 3 Information message when a user ADS web request exceeds the number of fields limit.
Datasets
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Table 2 Summary of the number of fields limits, as well as the major features of all ADS datasets (last reviewed on
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17 June 2021)
Dataset | Number of fields limit | Adaptor (indicates where the data are stored; see "Efficiency Tips" below) | Notes |
10000 | MARS Internal/external | Those variables listed as fast-access are readily available from ADS disks. Those variables listed as slow-access and data older than 30 days are stored in ECMWF MARS tape archive. | |
100000 | MARS Internal/external | Those variables listed as fast-access are readily available from ADS disks. Those variables listed as slow-access are stored in ECMWF MARS tape archive. | |
100000 | MARS Internal | N/A | |
CAMS global inversion-optimised greenhouse gas fluxes and concentrations | 500 | adaptor.url | Stored locally on ADS disks |
100000 | MARS external | Data are stored in ECMWF MARS tape archive | |
CAMS global greenhouse gas reanalysis (EGG4) monthly averaged fields | 100000 | MARS external | Data are stored in ECMWF MARS tape archive |
10000 | adaptor.cams_solar_rad2.retrieve | This data is calculated on demand by a service jointly provided by DLR, Armines, and Transvalor. The ADS forwards requests to this service and returns the data from it. | |
5000 | adaptor.cams_regional_fc.retrieve | There are three classes of speed at which these requests will be processed:
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1000 | adaptor.url2.retrieve | N/A | |
1000 | adaptor.url | ||
1000 | adaptor.url |
Efficiency tips
- Where the data are actually stored can make a significant difference in the speed at which a request is processed. ADS data hosted in 'MARS internal' is stored on ADS disks, and so is faster to retrieve. The 'MARS external' datasets are stored in the ECMWF MARS (tape) archive, and in this case it is important to request as much data as possible from the same tape file in your ADS request.
- It is better to submit small requests rather than very large requests. This will ensure your requests are not given a lower priority in the ADS request queue.
- When using the CDS API, it is strongly recommended that users take as a starting point the example API request script shown at the bottom of the ADS web 'Download data' page for the dataset of interest, and use this as the basis for your request.
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